[Docs] [txt|pdf]



Network Working Group                                Robert W. Scheifler
Request for Comments: 1013                                     June 1987



                  X WINDOW SYSTEM PROTOCOL, VERSION 11
                                 Alpha Update
                                  April 1987
     Copyright (c) 1986, 1987 Massachusetts Institute of Technology
                   X Window System is a trademark of M.I.T.


Status of this Memo

   This RFC is distributed to the Internet community for information
   only.  It does not establish an Internet standard.  The X window
   system has been widely reviewed and tested.  The internet community
   is encouraged to experiment with it.  Distribution of this memo is
   unlimited (see copyright notice on page 2).



































M.I.T.                                                          [Page 1]

RFC 1013                                                       June 1987


   Permission to use, copy, modify, and distribute this document for any
   purpose and without fee is hereby granted, provided that the above
   copyright notice appear in all copies and that both that copyright
   notice and this permission notice are retained, and that the name of
   M.I.T. not be used in advertising or publicity pertaining to this
   document without specific, written prior permission.  M.I.T. makes no
   representations about the suitability of this document or the
   protocol defined in this document for any purpose.  It is provided
   "as is" without express or implied warranty.

    Author: Robert W. Scheifler
           Laboratory for Computer Science
           545 Technology Square, Room 418
           Cambridge, MA 02139

    Contributors:
           Dave Carver (Digital HPW)
           Branko Gerovac (Digital HPW)
           Jim Gettys (MIT/Project Athena, Digital)
           Phil Karlton (Digital WSL)
           Scott McGregor (Digital SSG)
           Ram Rao (Digital UEG)
           David Rosenthal (Sun)
           Dave Winchell (Digital UEG)

    Implementors of initial server who provided useful input:
           Susan Angebranndt (Digital)
           Raymond Drewry (Digital)
           Todd Newman (Digital)

    Invited reviewers who provided useful input:
           Andrew Cherenson (Berkeley)
           Burns Fisher (Digital)
           Dan Garfinkel (HP)
           Leo Hourvitz (Next)
           Brock Krizan (HP)
           David Laidlaw (Stellar)
           Dave Mellinger (Interleaf)
           Ron Newman (MIT)
           John Ousterhout (Berkeley)
           Andrew Palay (ITC CMU)
           Ralph Swick (MIT)
           Craig Taylor (Sun)
           Jeffery Vroom (Stellar)

   This document does not attempt to provide the rationale or pragmatics
   required to fully understand the protocol or to place it in
   perspective within a  complete system.  Knowledge of X Version 10
   will certainly aid in understanding this document.





M.I.T.                                                          [Page 2]

RFC 1013                                                       June 1987


   The protocol contains many management mechanisms that are not
   intended for normal applications.  Not all mechanisms are needed to
   build a particular user interface.  It is important to keep in mind
   that the protocol is intended to provide mechanism, not policy.

   This document does not attempt to define precise formats or bit
   encodings.

   -------------------------------------------------------------------













































M.I.T.                                                          [Page 3]

RFC 1013                                                       June 1987


   SECTION 1.  TERMINOLOGY


   Access control list
           X maintains a list of hosts from which client programs may be
           run.  By default, only programs on the local host may use the
           display, plus any hosts specified in an initial list read by
           the server.  This "access control list" can be changed by
           clients on the local host.  Some server implementations may
           also implement other authorization mechanisms.

   Active grab
           A grab is "active" when the pointer or keyboard is actually
           owned by the single grabbing client.

   Ancestors
           If W is an inferior of A, then A is an "ancestor" of W.

   Atom
           An "atom" is a unique id corresponding to a string name.
           Atoms are used to identify properties, types, and selections.

   Backing store
           When a server maintains the contents of a window, the
           off-screen saved pixels are known as a "backing store".

   Bit gravity
           When a window is resized, the contents of the window are
           not necessarily discarded.  It is possible to request the
           server (though no guarantees are made) to relocate the
           previous contents to some region of the window.  This
           attraction of window contents for some location of a window
           is known as "bit gravity".

   Bitmap
           A "bitmap" is a pixmap of depth one.

   Button grabbing
           Buttons on the pointer may be passively "grabbed" by a
           client.  When the button is pressed, the pointer is then
           actively grabbed by the client.

   Byte order
           For image (pixmap/bitmap) data, byte order is defined by
           the server, and clients with different native byte ordering
            must swap bytes as necessary.  For all other parts of the
           protocol, the byte order is defined by the client, and the
           server swaps bytes as necessary.

   Children
           The "children" of a window are its first-level subwindows.



M.I.T.                                                          [Page 4]

RFC 1013                                                       June 1987


   Client
           An application program connects to the window system server
           by some interprocess communication (IPC) path, such as a TCP
           connection or a shared memory buffer.  This program is the
           window system server.  More precisely, the client is the IPC
           path itself; a program with multiple paths open to the server
           is viewed as multiple clients by the protocol.  Resource
           lifetimes are controlled by connection lifetimes, not by
           program lifetimes.

   Clipping regions
           In a graphics context, a bitmap or list of rectangles can
           be specified to restrict output to a particular region of
           the window.  The image defined by the bitmap or rectangles
           is called a "clipping region".

   Color cell
           An entry in a colormap is known as a "color cell".  An entry
           contains three values specifying red, green and blue
           intensities.  These values are always viewed as 16 bit
           unsigned numbers, with zero being minimum intensity.  The
           values are scaled by the server to match the display
           hardware.  The components of a cell are coincident with
           components of other cells in DirectColor and TrueColor
           colormaps.

   Colormap
           A "colormap" consists of a set of color cells.  A pixel value
           indexes the color map to produce intensities to be displayed.
           Depending on hardware limitations, one or more colormaps may
           be installed at one time, such that windows associated with
           those maps display with true colors.

   Connection
           The IPC path between the server and client program is known
           as a "connection".  A client program typically (but not
           necessarily) has one connection to the server over which
           requests and events are sent.

   Containment
           A window "contains" the pointer if the window is viewable and
           the hotspot of the cursor is within a visible region of the
           window or a visible region of one of its inferiors.  The
           border of the window is included as part of the window for
           containment.  The pointer is "in" a window if the window
           contains the pointer but no inferior contains the pointer.

   Coordinate system
           The coordinate system has X horizontal and Y vertical, with
           the origin [0, 0] at the upper left.  Coordinates are
           discrete, and in terms of pixels.  Each window and pixmap has



M.I.T.                                                          [Page 5]

RFC 1013                                                       June 1987


           its own coordinate system.  For a window, the origin is at
           the inside upper left, inside the border.

   Cursor
           A "cursor" is the visible shape of the pointer on a screen.
           It consist of a hot spot, a source bitmap, a shape bitmap,
           and a pair of colors.  The cursor defined for a window
           controls the visible appearance when the pinter is in that
           window.

   Depth
           The "depth" of a window or pixmap is number of bits per pixel
           it has. The depth of a gcontext is the depth of the root of
           the gcontext.

   Device
           Keyboards, mice, tablets, track-balls, button boxes, etc. are
           all collectively known as input "devices".  The core protocol
           only deals with two devices, "the keyboard" and "the
           pointer".

   Drawable
           Both windows and pixmaps may be used as sources and
           destinations  in graphics operations.  These are collectively
           known as "drawables". However, an InputOnly window cannot be
           used as a source or destination in a graphics operation.

   Event
           Clients are informed of information asynchronously via
           "events". These events may be either asynchronously generated
           from devices, or generated as side effects of client
           requests.  Events are grouped into types; events are never
           sent to a client by the server unless the client has
           specificially asked to be informed of that type of event,
           but other clients can force events to be sent to other
           clients. Events are typically reported relative to a window.

   Event mask
           Events are requested relative to a window.  The set of event
           types a client requests relative to a window described using
           an "event mask".

   Event sychronization
           There are certain race conditions possible when
           demultiplexing device events to clients (in particular
           deciding where pointer and keyboard events should be sent
           when in the middle of window management operations).  The
           event synchronization mechanism allows synchronous processing
           of device events.





M.I.T.                                                          [Page 6]

RFC 1013                                                       June 1987


   Event propagation
           Device-related events "propagate" from the source window to
           ancestor windows until some client has expressed interest in
           handling that type of event, or until the event is discarded
           explicitly.

   Event source
           The smallest window containing the pointer is the "source"
           of a device related event.

   Exposure event
           Servers do not guarantee to preserve the contents of windows
           when windows are obscured or reconfigur contents of regions
           of windows have been lost.

   Extension
           Named "extensions" to the core protocol can be defined to
           extend the system.  Extension to output requests, resources,
           and event types are all possible, and expected.

   Font
           A "font" is an array of glyphs (typically characters).  The
           protocol does no translation or interpretation of character
           sets.  The client simply indicates values used to index the
           glyph array.  A font contains additional metric information
           to determine inter-glyph and inter-line spacing.

   Glyph
           A "glyph" is an image, typically of a character, in a font.

   Grab
           Keyboard keys, the keyboard, pointer buttons, the pointer,
           and the server can be "grabbed" for exclusive use by a
           client.  In general, these facilities are not intended to be
           used by normal applications, but are intended for various
           input and window managers to implement various styles of
           user interfaces.

   Graphics context
           Various information for graphics output is stored in "GC"'s,
           such as foreground pixel, background pixel, line width,
           clipping region, etc.

   Hotspot
           A cursor has an associated "hot spot" which defines a point
           in the cursor that corresponds to the coordinates reported
           for the pointer.

   Identifier
           Each resource has an "identifier", a unique value associated
           with it that clients use to name the resource.  An identifier



M.I.T.                                                          [Page 7]

RFC 1013                                                       June 1987


           can be used over any connection to name the resource.

   Inferiors
           The "inferiors" of a window are all of the subwindows nested
           below it: the children, the children's children, etc.

   Input focus
           The "input focus" is nominally where keyboard input goes.
           Keyboard events are by default sent to the client expressing
           interest on the window the pointer is in.  This is said to be
           a "real estate driven" input focus.  It is also possible to
           attach the keyboard input to a  specific window; events will
           then be sent to the appropriate client independent of the
           pointer position.

   Input manager
           Control over keyboard input is typically provided by an
           "input manager" client.

   InputOnly window
           A window that cannot be used for graphics requests.
           InputOnly windows are "invisible", and can be used to control
           such things as cursors, input event generation, and grabbing.

   InputOutput window
           The "normal" kind of opaque window, used for both input
           and output.

   Key grabbing
           Keys on the keyboard may be passively "grabbed" by a client.
           When the key is pressed, the keyboard is then actively
           grabbed by the client.

   Keyboard grabbing
           A client can actively "grab" control of the keyboard, and key
           events will be sent to that client rather than the client the
           events would normally have been sent to.

   Mapping
           A window is said to be "mapped" if a map call has been
           performed on it.  Unmapped windows are never viewable or
           visible.

   Modifier keys
           Shift, Control, Meta, Super, Hyper, ALT, Compose, Apple,
           CapsLock, ShiftLock, and similar keys are called "modifier"
           keys.

   Obscures
           Window A "obscures" window B if both are viewable
           InputOutput windows and A is higher in the global stacking



M.I.T.                                                          [Page 8]

RFC 1013                                                       June 1987


           order, and the rectangle defined by the outside edges of
           intersects the rectangle defined by the outside edges of B.
           Note the (fine) distinction with "occludes". Also note that
           window borders are included in the calculation.

   Occludes
           Window A "occludes" window B if both are mapped and A is
           higher in the global stacking order, and the rectangle
           defined by the outside edges of A intersects the rectangle
           defined by the outside edges of B.  Note the (fine)
           distinction with "obscures".  Also note that window borders
           are included in the calculation.

   Padding
           Some padding bytes are inserted in the data stream to
           maintain alignment of the protocol requests on natural
           boundaries.  This increases ease of portability to some
           machine architectures.

   Parent window
           If C is a child of P, then P is the "parent" of C.

   Passive grab
           Grabbing a key or button is a "passive" grab.  The grab
           activates when the key or button is actually pressed.

   Pixel value
           A "pixel" is an N-bit value, where N is the number of bit
           planes used in a particular window or pixmap.  For a window,
           a pixel value indexes a colormap to derive an actual color
           to be displayed.

   Pixmap
           A "pixmap" is a three dimensional array of bits.  A pixmap
           is normally thought of as a two dimensional array of pixels,
           where each pixel can be a value from 0 to (2^N)-1, where N
           is the depth (z axis) of the pixmap.  A pixmap can also be
           thought of as a stack of N bitmaps.

   Plane mask
           Graphics operations can be restricted to only affect a
           subset of bit planes of a destination.  A "plane mask" is
           a bit mask describing which planes are to be modified, and
           is stored in a graphics context.

   Pointer
           The "pointer" is the pointing device attached to the cursor,
           and tracked on the screens.

   Pointer grabbing
           A client can actively "grab" control of the pointer, and



M.I.T.                                                          [Page 9]

RFC 1013                                                       June 1987


           button and motion events will be sent to that client rather
           than the client the events would normally have been sent to.

   Pointing device
           A "pointing device" is typically a mouse or tablet, or some
           other device with effective dimensional motion.  There is
           only one visible cursor is defined by the core protocol,
           and it tracks whatever pointing device is attached as the
           pointer.

   Property
           Windows may have associated "properties", consisting of a
           name, a type, a data format, and some data.  The protocol
           places no interpretation on properties, they are intended
           as a general-purpose naming mechanism for clients.  For
           example, clients might share information such as resize
           hints, program names, and icon formats with a window
           manager via properties.

   Property list
           The "property list" of a window is the list of properties
           that have been defined for the window.

   Redirecting control
           Window managers (or client programs) may wish to enforce
            window layout policy in various ways.  When a client
           attempts to change the size or position of a window, the
           operation may be "redirected" to a specified client,
           rather than the operation actually being performed.

   Reply
           Information requested by a client program is sent back to
           the client with a "reply".  Both events and replys are
           multipexed on the same connection.  Most requests do not
           generate replies.

   Request
           A command to the server is called a "request".  It is a
           single block of data sent over a connection.

   Resource
           Windows, pixmaps, cursors, fonts, graphics contexts, and
           colormaps are known as "resources".  They all have unique
           identifiers associated with them for naming purposes.  The
           lifetime of a resource is bounded by the lifetime of the
           connection over which the resource was created.

   Root
           The "root" of a pixmap or gcontext is the same as the root
           of whatever drawable was used when the pixmap or gcontext
           was created.  The "root" of a window is the root window



M.I.T.                                                         [Page 10]

RFC 1013                                                       June 1987


           under which the window was created.

   Root window
           Each screen has a "root window" covering it.  It cannot be
           reconfigured or unmapped, but otherwise acts as a full
           fledged window. A root window has no parent.

   Save set
           The "save set" of a client is a list of other client's
           windows which, if they are inferiors of one of the client's
           windows at connection close, should not be destroyed, and
           which should be remapped if it is unmapped.  Save sets are
           typically used by window managers to avoid lost windows if
           the manager should terminate abnormally.

   Screen
           A server may provide several independent "screens", which
           typically have physically independent monitors.  This would
           be the expected configuration when there is only a single
           keyboard and pointer shared among the screens.

   Server
           The "server" provides the basic windowing mechanism.  It
           handles IPC connections from clients, demultipexes graphics
           requests onto the screens, and multiplexes input back to the
           appropriate clients.

   Server grabbing
           The server can be "grabbed" by a single client for exclusive
           use. This prevents processing of any requests from other
           client connections until the grab is complete.  This is
           typically only a transient state for such things as
           rubber-banding and pop-up menus, or to execute requests
           indivisibly.

   Sibling
           Children of the same parent window are known as "sibling"
           windows.

   Stacking order
           Sibling windows may "stack" on top of each other.  Windows
           above both obscure and occlude lower windows.  This is
           similar to paper on a desk. The relationship between
           sibling windows is known as the "stacking order".

   Stipple
           A "stipple pattern" is a bitmap that is used to tile a
           region to serve as an additional clip mask for a fill
           operation with the foreground color.





M.I.T.                                                         [Page 11]

RFC 1013                                                       June 1987


   Tile
           A pixmap can be replicated in two dimensions to "tile"
           a region.  The pixmap itself is also known as a "tile".

   Timestamp
           A time value, expressed in milliseconds, typically since
           the last server reset.  Timestamp values wrap around (after
           about 49.7 days). The server, given its current time is
           represented by timestamp T, always interprets timestamps
           from clients by treating half of the timestamp space as
           being earlier in time than T, and half of the timestamp
           space as being later in time than T.  One timestamp value
           (named CurrentTime) is never generated by the server;
           this value is reserved for use in requests to represent
           the current server time.

   Type
           A type is an arbitrary atom used to identify the
           interpretation of property data.  Types are completely
           uninterpreted by the server; they are solely for the
           benefit of clients.

   Unviewable
           A window is "unviewable" if it is mapped but some ancestor is
           unmapped.

   Viewable
           A window is "viewable" if it and all of its ancestors are
           mapped.  This does not imply that any portion of the window
           is actually visible.

   Visible
           A region of a window is "visible" if someone looking at the
           screen can actually "see" it:  the window is viewable and the
           region is not occluded by any other window.

   Window gravity
           When windows are resized, subwindows may be repositioned
           automatically relative to some position in the window.  This
           attraction of a subwindow to some part of its parent is known
           as "window gravity".

   Window manager
           Manipulation of windows on the screen, and much of the user
           interface (policy) is typically provided by a "window
           manager" client.

   XYFormat
           The data for a pixmap is said to be in "XYFormat" if it is
           organized as a set of bitmaps representing individual bit
           planes.



M.I.T.                                                         [Page 12]

RFC 1013                                                       June 1987


   ZFormat
           The data for a pixmap is said to be in "ZFormat" if it is
           organized as a set of pixel values in scanline order.

SECTION 2.  PROTOCOL FORMATS


Request Format

   Every request contains an 8-bit "major" opcode, and a 16-bit length
   field expressed in units of 4 bytes.  Every request consists of 4
   bytes of header containing the major opcode, the length field, and a
   data byte) followed by zero or more additional bytes of data; the
   length field defines the total length of the request, including the
   header.  The length field in a request must equal the minimum length
   required to contain the request; if the specified length is smaller
   or larger than the required length, an error is enerated.  Unused
   bytes in a request are not required to be zero.  Major opcodes 128
   through 255 are reserved for extensions.  Extensions are intended
   to contain multiple requests, so extension requests typically have
   an additional minor opcode encoded in the "spare" data byte in the
   request header, but the placement and interpretation of this minor
   opcode, and all other fields in extension requests, are not defined
   by the core protocol. Every request is implicitly assigned a sequence
   number, starting with one,used in replies, errors, and events.

Reply Format

   Every reply contains a 32-bit length field expressed in units of 4
   bytes. Every reply consists of 32 bytes, followed by zero or more
   additional bytes of data, as specified in the length field.  Unused
   bytes within a reply are not guaranteed to be zero.  Every reply
   also contains the least significant 16 bits of the sequence number
   of the corresponding request.

Error Format

   Error reports are 32 bytes long.  Every error includes an 8-bit error
   code. Error codes 128 through 255 are reserved for extensions.  Every
   error also includes the major and minor opcodes of the failed
   request, and the least significant 16 bits of the sequence number of
   the request.  For the following errors (see Section 5), the failing
   resource id is also returned: Colormap, Cursor, Drawable, Font,
   GContext, IDChoice, Pixmap, and Window.  For Atom errors, the failing
   atom is returned.  For Value errors, the failing value is returned.
   Other core errors return no additional data.  Unused bytes within
   an error are not guaranteed to be zero.

Event Format

   Events are 32 bytes long.  Unused bytes within an event are not



M.I.T.                                                         [Page 13]

RFC 1013                                                       June 1987


   guaranteed to be zero.  Every event contains an 8-bit type code.  The
   most significant bit in this code is set if the event was generated
   from a SendEvent request. Event codes 64 through 127 are reserved for
   extensions, although the core protocol does not define a mechanism
   for selecting interest in such events. Every core event (with the
   exception of KeymapNotify) also contains the least significant 16
   bits of the sequence number of the last request issued by the client
   that was (or is currently being) processed by the server.


SECTION 3.  SYNTAX


   The syntax {...} encloses a set of alternatives.

   The syntax [...] encloses a set of structure components.

   In general, TYPEs are in upper case and AlternativeValues are
   capitalized.

   Requests in Section 10 are described in the following format:

       RequestName
               arg1: type1
               ...
               argN: typeN
           =>
               result1: type1
               ...
               resultM: typeM

               Errors: kind1, ..., kindK

               Description.

If no => is present in the description, then the request has no
reply (it is asynchronous), although errors may still be reported.

Events in Section 12 are described in the following format:

    EventName
            value1: type1
            ...
            valueN: typeN

            Description.








M.I.T.                                                         [Page 14]

RFC 1013                                                       June 1987


SECTION 4.  COMMON TYPES


LISTofFOO

   A type name of the form LISTofFOO means a counted list of elements
   of type FOO; the size of the length field may vary (it is not
   necessarily the same size as a FOO), in some cases may be implicit,
   and is not fully specified in this document.

BITMASK and LISTofVALUE

   The types BITMASK and LISTofVALUE are somewhat special.  Various
   requests contain arguments of the form:
           value-mask: BITMASK
           value-list: LISTofVALUE
   used to allow the client to specify a subset of a heterogeneous
   collection of "optional" arguments.  The value-mask specifies which
   arguments are to be provided; each such argument is assigned a unique
   bit position.  The representation of the BITMASK will typically
   contain more bits than there are defined arguments; unused bits in
   the value-mask must be zero (or the server generates a Value error).
   The value-list contains one value for each one bit in the mask, from
   least to most significant bit in the mask.  Each value is represented
   with 4 bytes, but the actual value occupies only the least
   significant bytes as required; the values of the unused bytes do not
   matter.

Or Types

   A type of the form "T1 or ... or Tn" means the union of the indicated
   types; a single-element type is given as the element without
   enclosing braces.

DEVICE: 32-bit id (<class,model,manufacturer,unit> 8 bits each)
WINDOW: 32-bit id
PIXMAP: 32-bit id
CURSOR: 32-bit id
FONT: 32-bit id
GCONTEXT: 32-bit id
COLORMAP: 32-bit id
DRAWABLE: WINDOW or PIXMAP
ATOM: 32-bit id (top 3 bits guaranteed to be zero)
VISUALID: 32-bit id (top 3 bits guaranteed to be zero)
VALUE: 32-bit quantity (used only in LISTofVALUE)
INT8: 8-bit signed integer
INT16: 16-bit signed integer
INT32: 32-bit signed integer
CARD8: 8-bit unsigned integer
CARD16: 16-bit unsigned integer
CARD32: 32-bit unsigned integer



M.I.T.                                                         [Page 15]

RFC 1013                                                       June 1987


TIMESTAMP: CARD32
BITGRAVITY: {Forget, Static,
             NorthWest, North, NorthEast,
             West, Center, East,
             SouthWest, South, SouthEast}
WINGRAVITY: {Unmap, Static,
             NorthWest, North, NorthEast,
             West, Center, East,
             SouthWest, South, SouthEast}
BOOL: {True, False}
EVENT: {KeyPress, KeyRelease,
        OwnerGrabButton,
        ButtonPress, ButtonRelease, EnterWindow, LeaveWindow,
        PointerMotion, PointerMotionHint,
        Button1Motion, Button2Motion, Button3Motion,
        Button4Motion, Button5Motion, ButtonMotion
        Exposure, VisibilityChange,
        StructureNotify, ResizeRedirect,
        SubstructureNotify, SubstructureRedirect,
        FocusChange,
        PropertyChange, ColormapChange,
        KeymapState}
POINTEREVENT: {ButtonPress, ButtonRelease, EnterWindow, LeaveWindow,
               PointerMotion, PointerMotionHint,
               Button1Motion, Button2Motion, Button3Motion,
               Button4Motion, Button5Motion, ButtonMotion
               KeymapState}
DEVICEEVENT: {KeyPress, KeyRelease,
              ButtonPress, ButtonRelease,
              PointerMotion,
              Button1Motion, Button2Motion, Button3Motion,
              Button4Motion, Button5Motion, ButtonMotion}
KEYCODE: CARD8
BUTTON: CARD8
KEYMASK: {Shift, CapsLock, Control, Mod1, Mod2, Mod3, Mod4, Mod5}
BUTMASK: {Button1, Button2, Button3, Button4, Button5}
KEYBUTMASK: KEYMASK or BUTMASK
STRING8: LISTofCARD8
STRING16: LISTofCHAR2B
CHAR2B: [byte1, byte2: CARD8]
POINT: [x, y: INT16]
RECTANGLE: [x, y: INT16,
            width, height: CARD16]
ARC: [x, y: INT16,
      width, height: CARD16,
      angle1, angle2: INT16]
HOST: [family: {Internet, NS, ECMA, Datakit, DECnet}
       address: LISTofCARD8]

   The [x,y] coordinates of a RECTANGLE specify the upper left corner.




M.I.T.                                                         [Page 16]

RFC 1013                                                       June 1987


   The primary interpretation of "large" characters in a STRING16 is
   that they are composed of two bytes used to index a 2-D matrix;
   hence the use of CHAR2B rather than CARD16.  This corresponds to
   the JIS/ISO method of indexing two-byte characters.  It is expected
   that most "large" fonts will be defined with two-byte matrix
   indexing.  For large fonts constructed with linear indexing, a
   CHAR2B can be interpreted as a 16-bit number by treating byte1 as
   the most significant byte; this means that clients should always
   transmit such 16-bit character values most significant byte first,
   as the server will never byte-swap CHAR2B quantities.

   The length, format, and interpretation of a HOST address are specific
   to the family.


SECTION 5.  ERRORS

   In general, when a request terminates with an error, the request has
   no side effects (i.e., there is no partial execution).  The only
   requests for which this is not true are ChangeWindowAttributes,
   ChangeGC, PolyText8, PolyText16, FreeColors, StoreColors, and
   ChangeKeyboardControl.

   The following error codes can be returned by the various requests:

Access
           An attempt to grab a key/button combination already grabbed
           by another client.

           An attempt to free a colormap entry not allocated by the
           client.

           An attempt to store into a read-only or an unallocated
           colormap entry.

           An attempt to modify the access control list from other than
           the local (or otherwise authorized) host.

           An attempt to select an event type, that at most one client
           can select at a time, when another client has already
           selected it.

Alloc
           The server failed to allocate the requested resource.

           Note that this only covers allocation errors at a very coarse
           level, and is not intended to (nor can it in practice hope
           to) cover all cases of a server running out of allocation
           space in the middle of service.





M.I.T.                                                         [Page 17]

RFC 1013                                                       June 1987


           The semantics when a server runs out of allocation space are
           left unspecified.

Atom
           A value for an ATOM argument does not name a defined ATOM.

Colormap
           A value for a COLORMAP argument does not name a defined
           COLORMAP.

Cursor
           A value for a CURSOR argument does not name a defined CURSOR.

Drawable
           A value for a DRAWABLE argument does not name a defined
           WINDOW or PIXMAP.

Font
           A value for a FONT or <FONT or GCONTEXT> argument does not
           name a defined FONT.

GContext
           A value for a GCONTEXT argument does not name a defined
           GCONTEXT.

IDChoice
           The value chosen for a resource identifier is either not
           included in the range assigned to the client, or is already
           in use.

Implementation
           The server does not implement some aspect of the request.  A
           server which generates this error for a core request is
           deficient.  As such, this error is not listed for any of the
           requests, but clients should be prepared to receive such
           errors, and handle or discard them.

Length
           The length of a request is shorter or longer than that
           required to minimally contain the arguments.

Match
           An InputOnly window is used as a DRAWABLE.

           Some argument (or pair of arguments) has the correct type and
           range, but fails to "match" in some other way required by the
           request.

Name
           A font or color of the specified name does not exist.




M.I.T.                                                         [Page 18]

RFC 1013                                                       June 1987


Pixmap
           A value for a PIXMAP argument does not name a defined PIXMAP.

Property
           The requested property does not exist for the specified
           window.

Request
           The major or minor opcode does not specify a valid request.

Value
           Some numeric value falls outside the range of values accepted
           by the request.  Unless a specific range is specified for an
           argument, the full range defined by the argument's type is
           accepted.  Any argument defined as a set of alternatives can
           generate this error.

Window
           A value for a WINDOW argument does not name a defined WINDOW.


Note:  the Atom, Colormap, Cursor, Drawable, Font, GContext, Pixmap,
and Window errors are also used when the argument type is extended
by union with a set of fixed alternatives, e.g.,<Window or
PointerRoot or None>.

SECTION 6.  KEYBOARDS

   Keycodes are always in the inclusive range [8,255].

   For keyboards with both left-side and right-side modifier keys (e.g.,
   Shift and Control), the mask bits in the protocol always define the
   OR of the keys. If electronically distinguishable, they can have
   separate up/down events generated, and clients that want to
   distinguish can track the individual states manually.

   <As part of the core we need to define a universal association
   between keycaps and keycodes.  A keycap is the graphical information
   imprinted on a keyboard key, e.g., "$ 4", "T", "+ =".>


SECTION 7.  POINTERS

   Buttons are always numbered starting with one.


SECTION 8.  PREDEFINED ATOMS

   Predefined atoms are not strictly necessary, and may not be useful in
   all environments, but will eliminate many InternAtom requests in most
   applications.  The core protocol imposes no semantics on these names,



M.I.T.                                                         [Page 19]

RFC 1013                                                       June 1987


   except as they are used in FONTPROP structures (see QueryFont).  Note
   that upper/lower case matters.

      BITMAP               ICON_SIZE               RGB_GREEN_MAP
      COMMAND              ITALIC_ANGLE            RGB_RED_MAP
      COPYRIGHT            MAX_SPACE               SECONDARY
      CUT_BUFFER0          MIN_SPACE               SIZE_HINTS
      CUT_BUFFER1          NAME                    STRIKEOUT_ASCENT
      CUT_BUFFER2          NORMAL_HINTS            STRIKEOUT_DESCENT
      CUT_BUFFER3          NORM_SPACE              STRING
      CUT_BUFFER4          PIXMAP                  SUBSCRIPT_X
      CUT_BUFFER5          POINT_SIZE              SUBSCRIPT_Y
      CUT_BUFFER6          PRIMARY                 SUPERSCRIPT_X
      CUT_BUFFER7          QUAD_WIDTH              SUPERSCRIPT_Y
      DEFAULT_CHAR         RECTANGLE               UNDERLINE_POSITION
      END_SPACE            RESIZE_HINT             UNDERLINE_THICKNESS
      FACE_NAME            RESOLUTION              WEIGHT
      FAMILY_NAME          RGB_BEST_MAP            WINDOW
      FONT_ASCENT          RGB_BLUE_MAP            WM_HINTS
      FONT_DESCENT         RGB_COLOR_MAP           X_HEIGHT
      ICON                 RGB_DEFAULT_MAP         ZOOM_HINTS
      ICON_NAME


SECTION 9.  CONNECTION SETUP

   For remote clients, the X protocol can be built on top of any
   reliable byte stream.  For TCP connections, displays on a given host
   a numbered starting from 0, and the server for display N listens and
   accepts connections on port 6000+N.

   The client must send an initial byte of data to identify the byte
   order to be employed.  The value of the byte must be octal 102 or
   154.  The value 102 (ASCII uppercase B) means values are transmitted
   most significant byte first, and value 154 (ASCII lowercase l) means
   values are transmitted least significant byte first.  Except where
   explicitly noted in the protocol, all 16-bit and 32-bit quantities
   sent by the client must be transmitted with this byte order, and all
   16-bit and 32-bit quantities returned by the server will be
   transmitted with this byte order.

   Following the byte-order byte, the following information is sent by
   the client at connection setup:

           protocol-major-version: CARD16
           protocol-minor-version: CARD16
           authorization-protocol-name: STRING8
           authorization-protocol-data: STRING8

           The version numbers indicate what version of the protocol the
           client expects the server to implement.  See below for an



M.I.T.                                                         [Page 20]

RFC 1013                                                       June 1987


           explanation. The authorization name indicates what
           authorization protocol the client expects the server to use,
           and the data is specific to that protocol. Specification of
           valid authorization mechanisms is not part of the core X
           protocol.  It is hoped that eventually one authorization
           protocol will be agreed upon.  In the mean time, a server
           that implements a different protocol than the client expects,
           or a server that only implements the host-based mechanism,
           will simply ignore this information.

   Received by the client at connection setup:
           success: BOOL
           protocol-major-version: CARD16
           protocol-minor-version: CARD16
           length: CARD16

           Length is the amount of additional data to follow, in units
           of 4 bytes. The version numbers are an escape hatch in case
           future revisions of the protocol are necessary.  In general,
           the major version would increment for incompatible changes,
           and the minor version would increment for small upward
           compatible changes.  Barring changes, the major version
           will be eleven, and the minor version will be zero.  The
           protocol version numbers returned indicate the protocol the
           server actually supports.  This might not equal the version
           sent by the client.  The server can (but need not) refuse
           connections from clients that offer a different version
           than the server supports.  A server can (but need not)
           support more than one version simultaneously.

   Additional data received if authorization fails:
           reason: STRING8

   Additional data received if authorization is accepted:
           vendor: STRING8
           release-number: CARD32
           resource-id-base, resource-id-mask: CARD32
           image-byte-order: {LSBFirst, MSBFirst}
           bitmap-format-scanline-unit: {8, 16, 32}
           bitmap-format-scanline-pad: {8, 16, 32}
           bitmap-format-bit-order: {LeastSignificant, MostSignificant}
           pixmap-formats: LISTofFORMAT
           roots: LISTofSCREEN
           keyboard: DEVICE
           pointer: DEVICE
           motion-buffer-size: CARD32
           maximum-request-length: CARD16

           where

             FORMAT: [depth: CARD8,



M.I.T.                                                         [Page 21]

RFC 1013                                                       June 1987


                      bits-per-pixel: {4, 8, 16, 24, 32}
                      scanline-pad: {8, 16, 32}]
             SCREEN: [root: WINDOW
                      device: DEVICE
                      width-in-pixels, height-in-pixels: CARD16
                      width-in-millimeters,height-in-millimeters:CARD16
                      allowed-depths: LISTofDEPTH
                      root-depth: CARD8
                      root-visual: VISUALID
                      default-colormap: COLORMAP
                      white-pixel, black-pixel: CARD32
                      min-installed-maps, max-installed-maps: CARD16
                      backing-stores: {Never, WhenMapped, Always}
                      save-unders: BOOL
                      current-input-masks: SETofEVENT]
            DEPTH: [depth: CARD8
                      visuals: LISTofVISUALTYPE]
            VISUALTYPE: [visual-id: VISUALID
                         class: {StaticGray, StaticColor,
                                 TrueColor,GrayScale, PseudoColor,
                                 DirectColor}
                                 red-mask, green-mask, blue-mask: CARD32
                                 bits-per-rgb-value: CARD8
                                 colormap-entries: CARD16]

   Per server information:

   The vendor string gives some indentification of the owner of the
   server implementation.  The semantics of the release-number is
   controlled by the vendor.

   The resource-id-mask contains a single contiguous set of bits (at
   least 18); the client allocates resource ids by choosing a value
   with (only) some subset of these bits set, and ORing it with
   resource-id-base.  Only values constructed in this way can be
   used to name newly created resources over this connection.
   Resource ids never have the top 3 bits set.  The client is not
   restricted to linear or contiguous allocation of resource ids.
   Once an id has been freed, it can be reused, but this should not
   be necessary. An id must be unique with respect to the ids of
   all other resources, not just other resources of the same type.

   Although the server is in general responsible for byte swapping
   data to match the client, images are always transmitted and
   received in formats (including byte order) specified by the
   server.  The byte order for images is given by image-byte-order,
   and applies to each scanline unit in XYFormat (bitmap) format,
   and to each pixel value in ZFormat.

   A bitmap is represented in scanline order.  Each scanline is padded
   to a multiple of bits as given by bitmap-format-scanline-pad.  The



M.I.T.                                                         [Page 22]

RFC 1013                                                       June 1987


   pad bits are of arbitrary value.  The scanline is quantized in
   multiples of bits as given by bitmap-format-scanline-unit.  Within
   each unit, the leftmost bit in the bitmap is either the least or
   most significant bit in the unit, as given by
   bitmap-format-bit-order.  If a pixmap is represented in XYFormat,
   each plane is represented as a bitmap, and the planes appear from
   most to least significant in bit order.

   For each pixmap depth supported by some screen, pixmap-formats lists
   the ZFormat used to represent images of that depth.  In ZFormat, the
   pixels are in scanline order, left to right within a scanline.  The
   number of bits used to hold each pixel is given by bits-per-pixel,
   and may be larger than strictly required by the depth.  When the
   bits-per-pixel is 4, the order of nibbles in the byte is the same as
   the image byte-order.  Each scanline is padded to a multiple of bits
   as given by scanline-pad.

   How a pointing device roams the screens is up to the server
   implementation, and is transparent to the protocol.  No geometry
   among screens is defined.

   The server may retain the recent history of pointer motion, and to a
   finer granularity than is reported by MotionNotify events.  Such
   history is available via the GetPointerMotions request.  The
   approximate size of the history buffer is given by
   motion-buffer-size.

   Maximum-request-length specifies the maximum length of a request, in
   4-byte units, accepted by the server; i.e., this is the maximum value
   that can appear in the length field of a request.  Requests larger
   than this generate a Length error, and the server will read and
   simply discard the entire request.  Maximum-request-length will
   always be at least 4096 (i.e., requests of length up to and including
   16384 bytes will be accepted by all servers).

   Per screen information:

   The allowed-depths specifies what pixmap and window depths are
   supported.  Pixmaps are supported for each depth listed, and windows
   of that depth are supported if at least one visual type is listed for
   the depth.  A pixmap depth of one is always supported and listed, but
   windows of depth one might not be supported.  A depth of zero is
   never listed, but zero-depth InputOnly windows are always supported.

   Root-depth and root-visual specify the depth and visual type of the
   root window.  Width-in-pixels and height-in-pixels specify the size
   of the root window (which cannot be changed).  The class of the root
   window is always InputOutput.  Width-in-millimeters and
   height-in-millimeters can be used to determine the physical size and
   the aspect ratio.




M.I.T.                                                         [Page 23]

RFC 1013                                                       June 1987


   The default-colormap is the one initially associated with the root
   window.  Clients with minimal color requirements creating windows of
   the same depth as the root may want to allocate from this map by
   default.

   Black-pixel and white-pixel can be used in implementing a
   "monochrome" application.  These pixel values are for permanently
   allocated entries in the default-colormap; the actual RGB values may
   be settable on some screens.

   The border of the root window is initially a pixmap filled with the
   black-pixel.  The initial background of the root window is a pixmap
   filled with some unspecified two-color pattern using black-pixel and
   white-pixel.

   Min-installed-maps specifies the number of maps that can be
   guaranteed to installed simultaneously (with InstallColormap),
   regardless of the number of entries allocated in each map.
   Max-installed-maps specifies the maximum number of maps that might
   possibly be installed simultaneously, depending on their
   allocations. For the typical case of a single hardware colormap,
   both values will be one.

   Backing-stores indicates when the server supports backing stores for
   this screen, although it may be storage limited in the number of
   windows it can support at once.  If save-unders is True, then the a
   server can support the save-under mode in CreateWindow and
   ChangeWindowAttributes, although again it may be storage limited.

   The current-input-events is what GetWindowAttributes would return for
   the all-event-masks for the root window.

   Per visual-type information:

   A given visual type might be listed for more than one depth, or for
   more than one screen.

   For PseudoColor, a pixel value indexes a colormap to produce
   independent RGB values; the RGB values can be changed dynamically.
   GrayScale is treated the same as PseudoColor, except which primary
   drives the screen is undefined, so the client should always store
   the same value for red, green, and blue in colormaps.  For
   DirectColor, a pixel value is decomposed into separate RGB
   subfields, and each subfield separately indexes the colormap for
   the corresponding value; The RGB values can be changed dynamically.
   TrueColor is treated the same as DirectColor, except the colormap
   has predefined read-only RGB values, which are server-dependent,
   but provide (near-)linear ramps in each primary.  StaticColor is
   treated the same as PseudoColor, except the colormap has
   predefined read-only RGB values, which are server-dependent.
   StaticGray is treated the same as StaticColor, except the red,



M.I.T.                                                         [Page 24]

RFC 1013                                                       June 1987


   green, and blue values are equal for any single pixel value,
   resulting in shades of gray.  StaticGray with a two-entry colormap
   can be thought of as "monochrome".

   The red-mask, green-mask, and blue-mask are only defined for
   DirectColor and TrueColor; each has one contiguous set of bits, with
   no intersections.

   The bits-per-rgb-value specifies the log base 2 of the approximate
   number of distinct color values (individually) of red, green, and
   blue. Actual RGB values are always passed in the protocol within a
   16-bit spectrum.

   The colormap-entries defines the number of available colormap entries
   in a newly created colormap.  For DirectColor and TrueColor, this
   will usually be the size of an individual pixel subfield.

SECTION 10.  REQUESTS


CreateWindow
           wid, parent: WINDOW
           class: {InputOutput, InputOnly, CopyFromParent}
           depth: CARD8
           visual: VISUALID or CopyFromParent
           x, y: INT16
           width, height, border-width: CARD16
           value-mask: BITMASK
           value-list: LISTofVALUE

           Errors: IDChoice, Window, Pixmap, Colormap, Cursor, Match,
           Value, Alloc

           Creates an unmapped window, and assigns the identifier wid
           to it.

           A class of CopyFromParent means the class is taken from the
           parent.  A depth of zero for class InputOutput or
           CopyFromParent means the depth is taken from the parent.
           A visual of CopyFromParent means the visual type is taken
           from the parent.  For class InputOutput, the visual type
           and depth must be a combination supported for the screen
           (else a Match error); the depth need not be the same as the
           parent, but the parent must not be of class InputOnly (else
           a Match error).  For class InputOnly, the depth must be
           zero (else a Match error), and the visual must be one
           supported for the screen (else a Match error), but the
           parent may have any depth and class.

           The server essentially acts as if InputOnly windows do not
           exist for the purposes of graphics requests, exposure



M.I.T.                                                         [Page 25]

RFC 1013                                                       June 1987


           processing, and VisibilityNotify events.  An InputOnly window
           cannot be used as a drawable (as a source or destination for
           graphics requests).  InputOnly and InputOutput windows act
           identically in other respects (properties, grabs, input
           control, and so on).

           The window is placed on top in the stacking order with
           respect to siblings.  The x and y coordinates are relative
           to the parent's origin, and specify the position of the upper
           left outer corner of the window (not the origin).  The width
           and height specify the inside size, not including the border,
           and must be non-zero.  The border-width for an InputOnly
           window must be zero (else a Match error).

           The value-mask and value-list specify attributes of the
           window that are to be explicitly initialized.  The possible
           values are:

               background-pixmap: PIXMAP or None or ParentRelative
               background-pixel: CARD32
               border-pixmap: PIXMAP or CopyFromParent
               border-pixel: CARD32
               bit-gravity: BITGRAVITY
               win-gravity: WINGRAVITY
               backing-store: {NotUseful, WhenMapped, Always}
               backing-bit-planes: CARD32
               backing-pixel: CARD32
               save-under: BOOL
               event-mask: SETofEVENT
               do-not-propagate-mask: SETofDEVICEEVENT
               override-redirect: BOOL
               colormap: COLORMAP or CopyFromParent
               cursor: CURSOR or None

           The default values, when attributes are not explicitly
           initialized, are:

               background-pixmap: None
               border-pixmap: CopyFromParent
               bit-gravity: Forget
               win-gravity: NorthWest
               backing-store: NotUseful
               backing-bit-planes: all ones
               backing-pixel: zero
               save-under: False
               event-mask: {} (empty set)
               do-not-propagate-mask: {} (empty set)
               override-redirect: False
               colormap: CopyFromParent
               cursor: None




M.I.T.                                                         [Page 26]

RFC 1013                                                       June 1987


           Only the following attributes are defined for InputOnly
           windows: win-gravity, event-mask, do-not-propagate-mask,
           and cursor.  It is a Match error to specify any other
           attributes for InputOnly windows.

           If background-pixmap is given, it overrides the default
           background-pixel.  The background pixmap and the window must
           have the same root and the same depth (else a Match error).
           Any size pixmap can be used, although some sizes may be
           faster than others.  If background None is specifed, the
           window has no defined background.  If background
           ParentRelative is specified, the parent's background is
           used, but the window must have the same depth as the parent
           (else a Match error); if the parent has background None,
           then the window will also have background None.  A copy
           of the parent's background is not made; the parent's
           background is reexamined each time the window background is
           required.  If background-pixel is given, it overrides the
           default and any background-pixmap given, and a pixmap of
           undefined size filled with background-pixel is used for the
           background.  For a  ParentRelative background, the
           background tile origin always aligns with the parent's
           background tile origin; otherwise the background tile
           origin is always the window origin.

           When regions of the window are exposed and the server has
           not retained the contents, the server automatically tiles
           the regions with the window's background unless the window
           has a background of None, in which case the previous screen
           contents are simply left in place. Exposure events are then
           generated for the regions, even if the  background is None.

           The border tile origin is always the same as the background
           tile origin.  If border-pixmap is given, it overrides the
           default border-pixel.  The border pixmap and the window must
           have the same root and the same depth (else a Match error).
           Any size pixmap can be used, although some sizes may faster
           than others.  If CopyFromParent is given, the parent's border
           pixmap is copied (subsequent changes to the parent do not
           affect the child), but the window must have the same depth
           as the parent (else a Match error).  If border-pixel is
           given, it overrides the default and any border-pixmap given,
           and a pixmap of undefined size filled with border-pixel is
           used for the border.

           Output to a window is always clipped to the inside of the
           window, so that the border is never affected.

           The bit-gravity defines which region of the window should be
           retained if the window is resized, and win-gravity defines
           how the window should be repositioned if the parent is



M.I.T.                                                         [Page 27]

RFC 1013                                                       June 1987


           resized; see ConfigureWindow.

           A backing-store of WhenMapped advises the server that
           maintaining contents of obscured regions when the window
           is mapped would be beneficial.  A backing-store of Always
           advises the server that maintaining contents even when the
           window is unmapped would be beneficial.  Note that, even if
           the window is larger than its parent, the server should
           maintain complete contents, not just the region within the
           parent boundaries.  If the server maintains contents,
           Exposure events will not be generated, but the server may
           stop maintaining contents at any time.  A value of NotUseful
           advises the server that maintaining contents is unnecessary,
           although a server may still choose to maintain contents.

           Backing-bit-planes indicates (with one bits) which bit
           planes of the window hold dynamic data that must be preserved
           in backing-stores. Backing-pixel specifies what value to use
           in planes not covered by backing-bit-planes.  The server is
           free to only save the specified bit planes in the
           backing-store, and regenerate the remaining planes with the
           specified pixel value.

           If save-under is True, the server is advised that, when
           this window is mapped, saving the contents of windows it
           obscures would be beneficial.

           The event-mask defines which events the client is interested
           in for this window (or, for some event types, inferiors of
           the window).  The do-not-propagate-mask defines which events
           should not be propagated to ancestor windows when no client
           has the event type selected in this window.

           Override-redirect specifies whether map and configure
           request on this window should override a SubstructureRedirect
           on the parent, typically to inform a window manager not to
           tamper with the window.

           The colormap specifies the colormap, that best reflects the
           "true" colors of the window.  Servers capable of supporting
           hardware colormaps may use this information, and window
           managers may use it for InstallColormap requests.  The
           colormap must have the same visual type as the window
           (else a match error). If CopyFromParent is specified, the
           parents's colormap is copied (subsequent changes to the
           parent do not affect the child), but the window must have
           the same visual type as the parent (else a Match error) an
           the parent must not have a colormap of None (else a Match
           error).





M.I.T.                                                         [Page 28]

RFC 1013                                                       June 1987


           If a cursor is specified, it will be used whenever the
           pointer is in the window.  If None is specified, the
           parent's cursor will be used when the pointer is in the
           window, and any change in the parent's cursor will
           cause an immediate change in the display cursor.

           This request generates a CreateNotify event.

           The background and border pixmaps and the cursor may be
           freed immediately if no further explicit references to
           them are to be made.

           Subsequent drawing into the background or border pixmap has
           an undefined effect on the window state; the server might or
           might not make a copy of the pixmap.

ChangeWindowAttributes
          window: WINDOW
          value-mask: BITMASK
          value-list: LISTofVALUE

          Errors: Window, Pixmap, Colormap, Cursor, Match, Value,
                  Access

          The value-mask and value-list specify which attributes are
          to be changed.  The values and restrictions are the same
          as for CreateWindow.

          Changing the background does not cause the window contents
          to be changed.  Setting the border, or changing the
          background such that border tile origin changes, causes the
          border to be repainted. Changing the background of a root
          window to None or ParentRelative restores the default
          background pixmap. Changing the border of a root window to
          CopyFromParent restores the default border pixmap.

           Changing the back-store of an obsecured window to
           WhenMapped or Always, or changing the backing-bit-planes,
           backing-pixel, or save-under of a mapped window, may have
           no immediate effect.

           Multiple clients can select input on the same window; their
           event-masks are disjoint.  When an event is generated it
           will be reported to all interested clients.  However, at
           most one client at a time can select for
           SubstructureRedirect, at most one client at a time can
           select for ResizeRedirectr, and at most one client at a
           time can select for ButtonPress.

           There is only one do-not-propagate-mask for a window, not
           one per client.



M.I.T.                                                         [Page 29]

RFC 1013                                                       June 1987


           Changing the colormap of a window (i.e., defining a new map,
           not changing the contents of the existing map) generates a
           ColormapNorify event.  Changing the colormap os a visible
           window may have no immediate effect on the screen; see
           InstallColormap.

           Changing the cursor of a root window to None restores the
           default cursor.

           The order in which attributes are verified and altered is
           server dependent. If an error is generated, a subset of
           the attributes may have been altered.

GetWindowAttributes
           window: WINDOW
       =>
           visual: VISUALID
           class: {InputOutput, InputOnly}
           bit-gravity: BITGRAVITY
           win-gravity: WINGRAVITY
           backing-store: {NotUseful, WhenMapped, Always}
           backing-bit-planes: CARD32
           backing-pixel: CARD32
           save-under: BOOL
           colormap: COLORMAP or None
           map-is-installed: BOOL
           map-state: {Unmapped, Unviewable, Viewable}
           all-event-masks, your-event-mask: SETofEVENT
           do-not-propagate-mask: SETofDEVICEEVENT
           override-redirect: BOOL

           Errors: Window

           Returns current attributes of the window.  All-event-masks
           is the inclusive-OR of all event masks selected on the
           window by clients.  Your-event-mask is the event mask
           selected by the querying client.

DestroyWindow
           window: WINDOW

           Errors: Window

           If the argument window is mapped, an UnmapWindow request is
           performed automatically.  The window and all inferiors are
           then destroyed, and a DestroyNotify event is generated for
           each window, in order from the argument window downwards,
           with unspecified order among siblings at each level.

           Normal exposure processing on formerly obscured windows is
           performed.



M.I.T.                                                         [Page 30]

RFC 1013                                                       June 1987


           If the window is a root window, this request has no effect.

DestroySubwindows
           window: WINDOW

           Errors: Window

           Performs a DestroyWindow on all children of the window, in
           bottom to top stacking order.

ChangeSaveSet
           window: WINDOW
           mode: {Insert, Delete}

           Errors: Window, Match, Value

           Adds or removes the specified window from the client's
           "save-set".  The window must have been created by some other
           client (else a Match error).  The use of the save-set is
           described in Section 11.

           Windows are removed automatically from the save-set by the
           server when they are destroyed.

ReparentWindow
           window, parent: WINDOW
           x, y: INT16

           Errors: Window, Match

           If the window is mapped, an UnmapWindow request is
           performed automatically first.  The window is then removed
           from its current position in the hierarchy, and is inserted
           as a child of the specified parent.  The x and y coordinates
           are relative to the parent's origin, and specify the new
           position of the upper left outer corner of the window.  The
           window is placed on top in the stacking order with respect
           to siblings.  A ReparentNotify event is then generated.  The
           override-redirect attribute of the window is passed on in
           this event; a value of True indicates that a window manager
           should not tamper with this window.  Finally, if the window
           was originally mapped, a MapWindow request is performed
           automatically.

           Normal exposure processing on formerly obscured windows is
           performed. The server might not generate exposure events for
           regions from the initial unmap that are immediately obscured
           by the final map.

           A Match error is generated if the new parent is not on the
           same screen as the old parent, or if the new parent is the



M.I.T.                                                         [Page 31]

RFC 1013                                                       June 1987


           window itself or an inferior of the window, or if the window
           has a ParentRelative background and the new parent is not
           the same depth as the window.

MapWindow
           window: WINDOW

           Errors: Window

           If the window is already mapped, this request has no effect.

           If the override-redirect attribute of the window is False and
           some other client has selected SubstructureRedirect on the
           parent, then a MapRequest event is generated, but the window
           remains unmapped. Otherwise, the window is mapped and a
           MapNotify event is generated.

           If the window is now viewable and its contents had been
           discarded, then the window is tiled with its background (if
           no background is defined the existing screen contents are not
           altered) and one or more exposure events are generated.  If a
           backing-store has been maintained while the window was
           unmapped, no exposure events are generated. If a
           backing-store will now be maintained, a full-window exposure
           is always generated; otherwise only visible regions may be
           reported. Similar tiling and exposure take place for any
           newly viewable inferiors.

MapSubwindows
           window: WINDOW

           Errors: Window

           Performs a MapWindow request on all unmapped children of the
           window, in top to bottom stacking order.

UnmapWindow
           window: WINDOW

           Errors: Window

           If the window is already unmapped, this request has no
           effect. Otherwise, the window is unmapped and an UnmapNotify
           event is generated.  Normal exposure processing on formerly
           obscured windows is performed.

UnmapSubwindows
           window: WINDOW

           Errors: Window




M.I.T.                                                         [Page 32]

RFC 1013                                                       June 1987


           Performs an UnmapWindow request on all mapped children of the
           window, in bottom to top stacking order.

ConfigureWindow
           window: WINDOW
           value-mask: BITMASK
           value-list: LISTofVALUE

           Errors: Window, Match, Value

           Changes the configuration of the window.  The value-mask and
           value-list specify which values are to be given.  The
           possible values are:

               x: INT16
               y: INT16
               width: CARD16
               height: CARD16
               border-width: CARD16
               sibling: WINDOW
               stack-mode: {Above, Below, TopIf, BottomIf, Opposite}

           The x and y coordinates are relative to the parent's origin,
           and specify the position of the upper left outer corner of
           the window. The width and height specify the inside size,
           not including the border, and must be non-zero.  It is a
           Match error to attempt to make the border-width of an
           InputOnly window non-zero.

           If the override-redirect attribute of the window is False
           and some other client has selected SubstructureRedirect on
           the parent, then a ConfigureRequest event is generated, and
           no further processing is performed.  Otherwise, the following
           is performed.

           If some other client has selected ResizeRedirect on the
           window and the width or height of the window is being
           changed, then a ResizeRequest event is generated, and the
           current width and height are used instead in the following.

           The geometry of the window is changed as specified and the
           window is restacked among siblings as described below, and a
           ConfigureNotify event is generated.  If the width or height
           of the window has actually changed, then children of the
           window are affected as described below.

           Exposure processing is performed on formerly obscured
           windows.

           Changing the width or height of the window causes its
           contents to be moved or lost, depending on the bit-gravity of



M.I.T.                                                         [Page 33]

RFC 1013                                                       June 1987


           the window, and causes children to be reconfigured, depending
           on their win-gravity.  For a change of width and height of W
           and H, we define the [x, y] pairs:

               NorthWest: [0, 0]
               North: [W/2, 0]
               NorthEast: [W, 0]
               West: [0, H/2]
               Center: [W/2, H/2]
               East: [W, H/2]
               SouthWest: [0, H]
               South: [W/2, H]
               SouthEast: [W, H]

           When a window with one of these bit-gravities is resized, the
           corresponding pair defines the change in position of each
           pixel in the window.  When a window with one of these
           win-gravities has its parent window resized, the
           corresponding pair defines the change in position of the
           window within the parent.  When a window is so repositioned,
           a GravityNotify event is generated.

           A gravity of Static indicates that the contents or origin
           should not move relative to the origin of the root window. If
           the change in size of the window is coupled with a change in
           position of [X, Y], then for bit-gravity the change in
           position of each pixel is [-X, -Y], and for win-gravity the
           change in position of a child when its parent is so resized
           is [-X, -Y].  Note that Static gravity still only takes
           effect when the width or height of the window is changed, not
           when the window is simply moved.

           A bit-gravity of Forget indicates that the window contents
           are always discarded after a size change; the window is tiled
           with its background (if no background is defined, the
           existing screen contents are not altered) and one or more
           exposure events are generated.  A server may also ignore the
           specified bit-gravity and use Forget instead.

           A win-gravity of Unmap is like NorthWest, but the child is
           also unmapped when the parent is resized, and an UnmapNotify
           event is generated.

           If a sibling and a stack-mode is specified, the window is
           restacked as follows:

               Above:  window is placed just above sibling
               Below:  window is placed just below sibling
               TopIf:  if sibling occludes window, then window is placed
                       at the top of the stack
               BottomIf:  if window occludes sibling, then window is



M.I.T.                                                         [Page 34]

RFC 1013                                                       June 1987


                          placed at the bottom of the stack
               Opposite:  if sibling occludes window, then window is
                          placed at the top of the stack, else if window
                          occludes sibling, then window is placed at the
                          bottom of the stack

           If a stack-mode is specified but no sibling is specified, the
           window is restacked as follows:

               Above:  window is placed at the top of the stack
               Below:  window is placed at the bottom of the stack
               TopIf:  if any sibling occludes window, then window is
                       placed at the top of the stack
               BottomIf: if window occludes any sibling, then window is
                         placed at the bottom of the stack
               Opposite: if any sibling occludes window, then window is
                         placed at the top of the stack, else if window
                         occludes any sibling, then window is placed at
                         the bottom of the stack

           It is a Match error if a sibling is specified without a
           stack-mode, or if the window is not actually a sibling.

           Note that the computations for BottomIf, TopIf, and Opposite
           are performed with respect to the window's final geometry
           (as controlled by the other arguments to the request), not
           its initial geometry.

CirculateWindow
           window: WINDOW
           direction: {RaiseLowest, LowerHighest}

           Errors: Window, Value

           If some other client has selected SubstructureRedirect on the
           window, then a CirculateRequest event is generated, and no
           further processing is performed.  Otherwise, the following is
           performed, and then a CirculateNotify event is generated if
           the window is actually restacked.

           For RaiseLowest, raises the lowest mapped child (if any) that
           is occluded by another child to the top of the stack.  For
           LowerHighest, lowers the highest mapped child (if any) that
           occludes another child to the bottom of the stack.  Exposure
           processing is performed on formerly obscured windows.

GetGeometry
           drawable: DRAWABLE
       =>
           root: WINDOW
           depth: CARD8



M.I.T.                                                         [Page 35]

RFC 1013                                                       June 1987


           x, y: INT16
           width, height, border-width: CARD16

           Errors: Drawable

           Returns the root and (current) geometry of the drawable.
           Depth is the number of bits per pixel for the object.
           X, y, and border-width will always be zero for pixmaps.
           For a window, the x and y coordinates specify the upper
           left outer corner of the window relative to its parent's
           origin, and the width and height specify the inside size
           (not including the border).

           It is legal to pass an InputOnly window as a drawable to
           this request.

QueryTree
           window: WINDOW
       =>
           root: WINDOW
           parent: WINDOW or None
           children: LISTofWINDOW

           Errors: Window

           Returns the root, the parent, and children of the window.
           The children are listed in bottom-to-top stacking order.

InternAtom
           name: STRING8
           only-if-exists: BOOL
       =>
           atom: ATOM or None

           Errors: Value, Alloc

           Returns the atom for the given name.  If only-if-exists is
           False, then the atom is created if it does not exist.  The
           string should use the ASCII encoding, and upper/lower case
           matters.

           The lifetime of an atom is not tied to the interning client.
           Atoms remained defined until server reset (see Section 11).

GetAtomName
           atom: ATOM
       =>
           name: STRING8

           Errors: Atom




M.I.T.                                                         [Page 36]

RFC 1013                                                       June 1987


           Returns the name for the given atom.

ChangeProperty
           window: WINDOW
           property, type: ATOM
           format: {8, 16, 32}
           mode: {Replace, Prepend, Append}
           data: LISTofINT8 or LISTofINT16 or LISTofINT32

           Errors: Window, Atom, Value, Match, Alloc

           Alters the property for the specified window.  The type is
           uninterpreted by the server.  The format specifies whether
           the data should be viewed as a list of 8-bit, 16-bit, or
           32-bit quantities, so that the server can correctly
           byte-swap as necessary.

           If mode is Replace, the previous property value is discarded.
           If the mode is Prepend or Append, then the type and format
           must match the existing property value (else a Match error);
           if the property is undefined, it is treated as defined with
           the correct type and format with zero-length data.  For
           Prepend, the data is tacked on to the beginning of the
           existing data, and for Append it is tacked on to the
           end of the existing data.

           Generates a PropertyNotify event on the window.

           The lifetime of a property is not tied to the storing client.
           Properties remain until explicitly deleted, or the window is
           destroyed, or until server reset (see Section 11).

           The maximum size of a property is server dependent.

DeleteProperty
           window: WINDOW
           property: ATOM

           Errors: Window, Atom

           Deletes the property from the specified window if the
           property exists. Generates a PropertyNotify event on the
           window unless the property does not exist.

GetProperty
           window: WINDOW
           property: ATOM
           type: ATOM or AnyPropertyType
           long-offset, long-length: CARD32
           delete: BOOL
       =>



M.I.T.                                                         [Page 37]

RFC 1013                                                       June 1987


           type: ATOM
           format: {8, 16, 32}
           bytes-after: CARD32
           value: LISTofINT8 or LISTofINT16 or LISTofINT32

           Errors: Window, Atom, Property, Match, Value

           If the specified property does not exist for the specifed
           window, a Property error is generated.  Otherwise, if type
           AnyPropertyType is specified, (part of) the property is
           returned regardless of its type; if a type is specified,
           (part of) the property is returned only if its type equals
           the specified type (else a Match error).  The actual type
           and format of the property are returned.

           Define the following values:
                   N = actual length of the stored property in bytes
                       (even if the format is 16 or 32)
                   I = 4 * long-offset
                   T = N - I
                   L = MINIMUM(T, 4 * long-length)
                   A = N - (I + L)
           The returned value starts at byte index I in the property
           (indexing from 0), and its length in bytes is L.  It is a
           Value error if long-offset is given such that L is negative.
           The value of bytes-after is A, giving the number of trailing
           unread bytes in the stored property.

           If delete is True and bytes-after is zero, the property is
           also deleted from the window and a PropertyNotify event is
           generated on the window.

RotateProperties
           window: WINDOW
           delta: INT8
           properties: LISTofATOM

           Errors: Window, Atom, Match

           If the property names in the list are viewed as being
           numbered starting from zero, and there are N property names
           in the list, then the value associated with property name I
           becomes the value associated with property name (I + delta)
           mod N, for all I from zero to N - 1.  The effect is to rotate
           the states by delta places around the virtual ring of
           property names (right for positive delta, left for negative
           delta).

           A PropertyNotify event is generated for each property, in the
           order listed.




M.I.T.                                                         [Page 38]

RFC 1013                                                       June 1987


           If an atom occurs more than once in the list or no property
           with that name is defined for the window, a Match error is
           generated.  If an Atom or Match error is generated, no
           properties are changed.

ListProperties
           window: WINDOW
       =>
           atoms: LISTofATOM

           Errors: Window

           Returns the atoms of properties currently defined on the
           window.

SetSelectionOwner
           selection: ATOM
           owner: WINDOW or None
           time: TIMESTAMP or CurrentTime

           Error: Atom, Window

           Changes the owner and last-change time of the specifed
           selection.  The request has no effect if the specified time
           is earlier than the current last-change time of the specified
           selection or is later than the current server time;
           otherwise, the last-change time is set to the specified time,
           with CurrentTime replaced by the current server time.
           If the new owner is not the same as the current owner of the
           selection, and the current owner is a window, then the
           current owner is sent a SelectClear event.

           If the owner of a selection is a window, and the window is
           later destroyed, the owner of the selection automatically
           reverts to None, but the last-change time is not affected.

           The selection atom is uninterpreted by the server.

           Selections are global to the server.

GetSelectionOwner
           selection: ATOM
       =>
           owner: WINDOW or None

           Errors: Atom

           Returns the current owner of the specified selection, if any.

ConvertSelection
           selection, target: ATOM



M.I.T.                                                         [Page 39]

RFC 1013                                                       June 1987


           property: ATOM or None
           requestor: WINDOW
           time: TIMESTAMP or CurrentTime

           Error: Atom, Window

           If the specified selection is owned by a window, the server
           sends a SelectionRequest event to the owner.  If no owner for
           the specified selection exists, the server generates a
           SelectionNotify event to the requestor with property None.
           The arguments are passed on unchanged in either event.

SendEvent
           destination: WINDOW or PointerWindow or InputFocus
           propagate: BOOL
           event-mask: SETofEVENT
           event: <normal-event-format>

           Errors: Window, Value

           If PointerWindow is specified, destination is replaced with
           the window that the pointer is in.  If InputFocus is
           specified, then if the focus window contains the pointer,
           destination is replaced with the window that the pointer is
           in, and otherwise destination is replaced with the focus
           window.

           If propagate is False, then the event is sent to every client
           selecting on destination any of the event types in
           event-mask.

           If propagate is True and no clients have selected on
           destination any of the event types in event-mask, then
           destination is replaced with the closest ancestor of
           destination for which some client has selected a type in
           event-mask and no intervening window has that type in its
           do-not-propagate-mask.  If no such window exists, or if the
           window is an ancestor of the focus window and InputFocus was
           originally specified sent to any clients. Otherwise, the
           event is reported to every client selecting on the final
           destination any of the types specified in event-mask.

           The event code must be one of the core events, or one of
           the events defined by an extension, so that the server can
           correctly byte swap the contents as necessary.  The
           contents of the event are otherwise unaltered and unchecked
           by the server except to force on the most significant bit
           of the event code.






M.I.T.                                                         [Page 40]

RFC 1013                                                       June 1987


           Active grabs are ignored for this request.

GrabPointer
           grab-window: WINDOW
           owner-events: BOOL
           event-mask: SETofPOINTEREVENT
           pointer-mode, keyboard-mode: {Synchronous, Asynchronous}
           confine-to: WINDOW or None
           cursor: CURSOR or None
           time: TIMESTAMP or CurrentTime
       =>
           status: {Success, AlreadyGrabbed, Frozen, InvalidTime,
                    NotViewable}

           Errors: Cursor, Window, Value

           Actively grabs control of the pointer.  Further pointer
           events are only reported to the grabbing client.  The
           request overrides any active pointer grab by this client.

           Event-mask is always augmented to include ButtonPress and
           ButtonRelease.  If owner-events is False, all generated
           pointer events are reported with respect to grab-window,
           and are only reported if selected by event-mask.  If
           owner-events is True, then if a generated pointer event
           would normally be reported to this client, it is reported
           normally; otherwise the event is reported with respect to
           the grab-window, and is only reported if selected by
           event-mask.  For either value of owner-events, unreported
           events are simply discarded.

           Pointer-mode controls further processing of pointer events,
           and keyboard-mode controls further processing of keyboard
           events.  If the mode is Asynchronous, event processing
           continues normally; if the device is currently frozen by
           this client, then processing of events for the device is
           resumed.  If the mode is Synchronous, the device (as seen
           via the protocol) appears to freeze, and no further events
           for that device are generated by the server until the
           grabbing client issues a releasing AllowEvents request.
           Actual device changes are not lost while the device is
           frozen; they are simply queued for later processing.

           If a cursor is specified, then it is displayed regardless
           of what window the pointer is in.  If no cursor is
           specified, then when the pointer is in grab-window or one
           of its subwindows, the normal cursor for that window is
           displayed, and otherwise the cursor for grab-window is
           displayed.





M.I.T.                                                         [Page 41]

RFC 1013                                                       June 1987


           If a confine-to window is specified, then the pointer
           will be restricted to stay contained in that window.
           The confine-to  window need have no relationship to the
           grab-window.  If the pointer is not initially in the
           confine-to window, then it is warped automatically to
           the closest edge (and enter/leave events generated
           normally) just  before the grab activates.  If the
           confine-to window is subsequently reconfigured, the
           pointer will be warped automatically as necessary to keep
           it contained in the window.

           This request generates EnterNotify and LeaveNotify events.

           The request fails with status AlreadyGrabbed if the
           pointer is actively grabbed by some other client.  The
           request fails with status Frozen if the pointer is frozen
           by an active grab of another client.  The request fails
           with status NotViewable if grab-window or
           confine-to window is not viewable.  The request fails with
           status InvalidTime if the specified time is earlier than
           the last-pointer-grab time or later than the current
           server time; otherwise the last-pointer-grab time is set
           to the specified time, with CurrentTime replaced by the
           current server time.

UngrabPointer
           time: TIMESTAMP or CurrentTime

           Releases the pointer if this client has it actively
           grabbed (from either GrabPointer or GrabButton or from a
           normal button press), and releases any queued events. The
           request has no effect if the specified time is earlier
           than the last-pointer-grab time or is later than the
           current server time.

           This request generates EnterNotify and LeaveNotify events.

           An UngrabPointer is performed automatically if the event
           window or confine-to window for an active pointer grab
           becomes not viewable.

GrabButton
           modifiers: SETofKEYMASK or AnyModifier
           button: BUTTON or AnyButton
           grab-window: WINDOW
           owner-events: BOOL
           event-mask: SETofPOINTEREVENT
           pointer-mode, keyboard-mode: {Synchronous, Asynchronous}
           confine-to: WINDOW or None
           cursor: CURSOR or None




M.I.T.                                                         [Page 42]

RFC 1013                                                       June 1987


           Errors: Cursor, Window, Value, Access

           This request establishes a passive grab.  In the future,
           if the specified button is pressed when the specified
           modifier keys are down (and no other buttons or modifier
           keys are down), and grab-window contains the pointer,
           and the confine-to window (if any) is viewable, and these
           constraints are not satisfied for any ancestor, then the
           pointer is actively grabbed as described in GrabPointer,
           the last-pointer-grab time is set to the time at which
           the button was pressed (as transmitted in the ButtonPress
           event), and the ButtonPress event is reported.  The
           interpretation of the remaining arguments is as for
           GrabPointer.  The active grab is terminated automatically
           when all buttons are released (independent of the state
           of modifier keys).

           A modifiers of AnyModifier is equivalent to issuing the
           request for all possible modifier combinations.  A
           button of AnyButton is equivalent to issuing the request
           for all possible buttons.

           An Access error is generated if some other client has
           already issued a GrabButton with the same button/key
           combination on the same window. When using AnyModifier
           or AnyButton, the request fails completely (no grabs are
           established) if there is a combination.  The request has
           no effect on an active grab.

UngrabButton
           modifiers: SETofKEYMASK or AnyModifier
           button: BUTTON or AnyButton
           grab-window: WINDOW

           Errors: Window

           Releases the passive button/key combination on the
           specified window if it was grabbed by this client. A
           modifiers of AnyModifier is equivalent to issuing the
           request for all possible modifier combinations.  A
           button of AnyButton is equivalent to issuing the request
           for all possible buttons. Has no effect on an active
           grab.

ChangeActivePointerGrab
           event-mask: SETofPOINTEREVENT
           cursor: CURSOR or None
           time: TIMESTAMP or CurrentTime

           Errors: Cursor




M.I.T.                                                         [Page 43]

RFC 1013                                                       June 1987


           Changes the specified dynamic parameters if the pointer
           is actively grabbed by the client and the specified time
           is no earlier than the last-pointer-grab time and no
           later than the current server time.  The interpretation
           of event-mask and cursor are as in GrabPointer.  The
           event-mask is always augmented to include ButtonPress
           and ButtonRelease.  Has no effect on the passive
           parameters of a GrabButton.

GrabKeyboard
           grab-window: WINDOW
           owner-events: BOOL
           pointer-mode, keyboard-mode: {Synchronous, Asynchronous}
           time: TIMESTAMP or CurrentTime
       =>
           status: {Success, AlreadyGrabbed, Frozen, InvalidTime,
                    NotViewable}

           Errors: Window, Value

           Actively grabs control of the keyboard.  Further key
           events are reported only to the grabbing client.  The
           request overrides any active keyboard grab by this
           client.

           If owner-events is False, all generated key events are
           reported with respect to grab-window.  If owner-events is
           True, then if a generated key event would normally be
           reported to this client, it is reported normally;
           otherwise the event is reported with respect to the
           grab-window.  Both KeyPress and KeyRelease events are
           always reported, independent of any event selection made
           by the client.

           Pointer-mode controls further processing of pointer
           events, and keyboard-mode controls further processing of
           keyboard events.  If the mode is Asynchronous, event
           processing continues normally; if the device is currently
           frozen by this client, then processing of events for the
           device is resumed.  If the mode is Synchronous, the
           device (as seen via the protocol) appears to freeze, and
           no further events for that device are generated by the
           server until the grabbing client issues a releasing
           AllowEvents request.  Actual device changes are not lost
           while the device is frozen; they are simply queued for
           later processing.

           This request generates FocusIn and FocusOut events.

           The request fails with status AlreadyGrabbed if the
           keyboard is actively grabbed by some other client.  The



M.I.T.                                                         [Page 44]

RFC 1013                                                       June 1987


           request fails with status Frozen if the keyboard is
           frozen by an active grab of another client. The request
           fails with status NotViewable if grab-window is not
           viewable.  The request fails with status InvalidTime if
           the specified time is earlier than the last-keyboard-grab
           time or later than the current server time; otherwise the
           last-keyboard-grab time is set to the specified time,
           with CurrentTime replaced by the current server time.

UngrabKeyboard
           time: TIMESTAMP or CurrentTime

           Releases the keyboard if this client has it actively
           grabbed (from either GrabKeyboard or GrabKey), and
           releases any queued events.  The request has no effect
           if the specified time is earlier than the
           last-keyboard-grab time or is later than the current
           server time.

           This request generates FocusIn and FocusOut events.

           An UngrabKeyboard is performed automatically if the event
           window for an active keyboard grab becomes not viewable.

GrabKey
           key: KEYCODE or AnyNonModifier
           modifiers: SETofKEYMASK or AnyModifier
           grab-window: WINDOW
           owner-events: BOOL
           pointer-mode, keyboard-mode: {Synchronous, Asynchronous}

           Errors: Window, Value, Access

           This request establishes a passive grab on the keyboard.
           In the future, if the specified key (which can itself be a
           modifier key) is pressed when the specified modifier keys
           are down (and no other modifier keys are down), and the
           KeyPress event would be generated in grab-window or one of
           its inferiors, and these constraints are not satisfied for
           any ancestor, then the keyboard is actively grabbed as
           described in GrabKeyboard, the last-keyboard-grab time is
           transmitted in set to the time at which the key was
           pressed (as in the KeyPress event), and the KeyPress
           event is reported.  The interpretation of the remaining
           arguments is as for GrabKeyboard.  The active grab is
           terminated automatically when the specified key has been
           released (independent of the state of the modifier keys).

           A modifiers of AnyModifier is equivalent to issuing the
           request for all possible modifier combinations.  A key of
           AnyNonModifier is equivalent to issuing the request for



M.I.T.                                                         [Page 45]

RFC 1013                                                       June 1987


           all possible non-modifier key codes.

           An Access error is generated if some other client has
           issued a GrabKey with the same key combination on the
           same window. When using AnyModifier or AnyNonModifier,
           the request fails  completely (no grabs are established)
           if there is a conflicting grab for any combination.

UngrabKey
           key: KEYCODE or AnyNonModifier
           modifiers: SETofKEYMASK or AnyModifier
           grab-window: WINDOW

           Errors: Window

           Releases the key combination on the specified window if it
           was grabbed by this client.  A modifiers of AnyModifier is
           equivalent to issuing the request for all possible
           modifier combinations.  A key of AnyNonModifier is
           equivalent to issuing the request for all possible
           non-modifier key codes.  Has no effect on an active grab.

AllowEvents
           mode: {AsyncPointer, SyncPointer, ReplayPointer,
                  AsyncKeyboard, SyncKeyboard, ReplayKeyboard}
           time: TIMESTAMP or CurrentTime

           Errors: Value

           Releases some queued events if the client has caused a
           device to freeze.  The request has no effect if the
           specified time is earlier than the last-grab time of the
           most recent active grab for the client, or if the
           specified time is later than the current server time.

           For AsyncPointer, if the pointer is frozen by the client,
           pointer event processing continues normally.  If the
           pointer is frozen twice by the client on behalf of two
           separate grabs, AsyncPointer "thaws" for both.
           AsyncPointer has no effect if the pointer is not frozen
           by the client, but the pointer need not be grabbed by
           the client.

           For SyncPointer, if the pointer is frozen and actively
           grabbed by the client, pointer event processing continues
           normally until the next ButtonPress or ButtonRelease event
           is reported to the client, at which time the pointer again
           appears to freeze.  However if the reported event causes
           the pointer grab to be released, then the pointer does not
           freeze.  SyncPointer has no effect if the pointer is not
           frozen by the client, or if the pointer is not grabbed by



M.I.T.                                                         [Page 46]

RFC 1013                                                       June 1987


           the client.

           For ReplayPointer, if the pointer is actively grabbed by
           the client and is frozen as the result of an event having
           been sent to the client (either from the activation of a
           GrabButton, or from a previous AllowEvents with mode
           SyncPointer, but not from a GrabPointer), then the pointer
           grab is released and that event is completely reprocessed,
           but this time ignoring any passive grabs at or above
           (towards the root) the grab-window of the grab just
           released.  The request has no effect if the pointer is
           not grabbed by the client, or if the pointer is not
           frozen as the result of an event.

           For AsyncKeyboard, if the keyboard is frozen by the
           client, keyboard event processing continues normally.  If
           the pointer is frozen twice by the client on behalf of
           two separate grabs, AsyncPointer "thaws" for both.
           AsyncKeyboard has no effect if the keyboard is not
           frozen by the client, but the keyboard need not be
           grabbed by the client.

           For SyncKeyboard, if the keyboard is frozen and actively
           grabbed by the client, keyboard event processing
           continues normally until the next KeyPress or KeyRelease
           event is  reported to the client, at which time the
           keyboard again appears to freeze.  However if the
           reported event causes the keyboard grab to be released,
           then the keyboard does not freeze.  SyncKeyboard has no
           effect if the keyboard is not frozen by the client, or
           if the keyboard is not grabbed by the client.

           For ReplayKeyboard, if the keyboard is actively grabbed
           by the client and is frozen as the result of an event
           having been sent to the client  (either from the
           activation of a GrabKey, or from a previous AllowEvents
           with mode SyncKeyboard, but not from a GrabKeyboard),
           then the keyboard grab is released and that event is
           completely reprocessed, but this time ignoring any passive
           grabs at or above (towards the root) the grab-window of
           the grab just released.  The request has no effect if the
           keyboard is not grabbed by the client, or if the keyboard
           is notfrozen as the result of an event.

           AsyncPointer, SyncPointer, and Replay Pointer have no
           effect on processing of keyboard events.  AsyncKeyboard,
           SyncKeyboard, and ReplayKeyboard have no effect on
           processing of pointer events.

           It is possible for both a pointer grab and a keyboard grab
           to be active simultaneously (by the same or different



M.I.T.                                                         [Page 47]

RFC 1013                                                       June 1987


           clients).  If a device is frozen on behalf of either grab,
           no event processing is performed for the device.  It is
           possible for a single device to be frozen due to both
           grabs.  In this case, the freeze must be released on
           behalf of both grabs before events can again be
           processed.

GrabServer
           Disables processing of requests and close-downs on all
           other connections (than the one this request arrived on).

UngrabServer
           Restarts processing of requests and close-downs on other
           connections.

QueryPointer
           window: WINDOW
       =>
           root: WINDOW
           child: WINDOW or None
           same-screen: BOOL
           root-x, root-y, win-x, win-y: INT16
           mask: SETofKEYBUTMASK

           Errors: Window

           The root window the pointer is currently on, and pointer
           coordinates relative to the root's origin, are returned.
           If same-screen is False, then the pointer is not on the
           same screen as the argument window, and child is None and
           win-x and win-y are zero.  If same-screen is True, then
           win-x and win-y are the pointer coordinates relative to
           the argument window's origin, and child is the child
           containing the pointer, if any.  The current state of the
           modifier keys and the buttons are also returned.

GetMotionEvents
           start, stop: TIMESTAMP or CurrentTime
           window: WINDOW
       =>
           events: LISTofTIMECOORD

           where
                   TIMECOORD: {x, y: CARD16
                               time: TIMESTAMP}

           Error: Window

           Returns all events in the motion history buffer that fall
           between the specified start and stop times (inclusive)
           and that have coordinates that lie within (including



M.I.T.                                                         [Page 48]

RFC 1013                                                       June 1987


           borders) the specified window at its present placement.
           The x and y coordinates are reported relative to the
           origin  of the window.

TranslateCoordinates
           src-window, dst-window: WINDOW
           src-x, src-y: INT16
       =>
           same-screen: BOOL
           child: WINDOW or None
           dst-x, dst-y: INT16

           Errors: Window

           The src-x and src-y coordinates are taken relative to
           src-window's origin, and returned as dst-x and dst-y
           coordinates relative to dst-window's origin.  If
           same-screen is False, then src-window and dst-window are
           on different screens, and dst-x and dst-y are zero.  If
           the coordinates are contained in a mapped child of
           dst-window, then that child is returned.

WarpPointer
           src-window: WINDOW or None
           dst-window: WINDOW
           src-x, src-y: INT16
           src-width, src-height: CARD16
           dst-x, dst-y: INT16

           Errors: Window

           Moves the pointer to [dst-x, dst-y] relative to
           dst-window's origin. If src-window is None, the move is
           independent of the current pointer position, but if a
           window is specified, the move only takes place if the
           pointer is currently contained in a visible portion of
           the specified rectangle of the src-window.

           The src-x and src-y coordinates are relative to
           src-window's origin.  If src-height is zero, it is
           replaced with the current height of src-window minus
           src-y.  If src-width is zero, it is replaced with the
           current width of src-window minus src-x.

           This request cannot be used to move the pointer outside
           the confine-to window of an active pointer grab; an
           attempt will only move the pointer as far as the closest
           edge of the confine-to window.






M.I.T.                                                         [Page 49]

RFC 1013                                                       June 1987


SetInputFocus
           focus: WINDOW or PointerRoot or None
           revert-to: {Parent, PointerRoot, None}
           time: TIMESTAMP or CurrentTime

           Errors: Window, Value

           Changes the input focus and the last-focus-change time.
           The request has no effect if the specified time is earlier
           than the current last-focus-change time or is later than
           the current server time; otherwise, the last-focus-change
           time is set to the specified time, with CurrentTime
           replaced by the current server time.

           If None is specified as the focus, all keyboard events are
           discarded until a new focus window is set.  In this case,
           therevert-to argument is ignored.

           If a window is specified as the focus, it becomes the
           keyboard's focus window.  If a generated keyboard event
           would normally be reported to this window or one of its
           inferiors, the event is reported normally; otherwise, the
           event is reported with respect to the focus window.

           If PointerRoot is specified as the focus, the focus
           window is dynamically taken to be the root window of
           whatever screen the pointer is on at each keyboard event.
           In this case, the revert-to argument is ignored.

           This request generates FocusIn and FocusOut events.

           If the focus window becomes not viewable, the new focus
           window depends on the revert-to argument.  If revert-to
           is Parent, the focus reverts to the parent (or the
           closest viewable ancestor) and the new revert-to value is
           take to be None.  If revert-to is PointerRoot or None,
           the focus reverts to that value.  When the focus reverts,
           FocusIn and FocusOut events are generated, but the
           last-focus-change time is not affected.

GetInputFocus
           =>
           focus: WINDOW or PointerRoot or None
           revert-to: {Parent, PointerRoot, None}

           Returns the current focus state.

QueryKeymap
       =>
           keys: LISTofCARD8




M.I.T.                                                         [Page 50]

RFC 1013                                                       June 1987


           Returns a bit vector for the keyboard; each one bit
           indicates that the corresponding key is currently pressed.
           The vector is represented as 32 bytes.  Byte N (from 0)
           contains the bits for keys 8N to 8N+7, with the least
           significant bit in the byte representing key 8N.

OpenFont
           fid: FONT
           name: STRING8

           Errors: IDChoice, Name, Alloc

           Loads the specified font, if necessary, and associates
           identifier fid with it.  The font can be used as a source
           for any drawable.  The font name should use the ASCII
           encoding, and upper/lower case does not matter.

CloseFont
           font: FONT

           Errors: Font

           Deletes the association between the resource id and the
           font.  The font itself will be freed when no other
           resource references it.

QueryFont
           font: FONT or GCONTEXT
       =>
           font-info: FONTINFO
           char-infos: LISTofCHARINFO

           where
                   FONTINFO: [draw-direction: {LeftToRight, RightToLeft}
                              min-char-or-byte2,max-char-or-byte2:CARD16
                              min-byte1, max-byte1: CARD8
                              all-chars-exist: BOOL
                              default-char: CARD16
                              min-bounds: CHARINFO
                              max-bounds: CHARINFO
                              font-ascent: INT16
                              font-descent: INT16
                              properties: LISTofFONTPROP]
                   FONTPROP: [name: ATOM
                              value: INT32 or CARD32]
                   CHARINFO: [left-side-bearing: INT16
                              right-side-bearing: INT16
                              character-width: INT16
                              ascent: INT16
                              descent: INT16
                              attributes: CARD16]



M.I.T.                                                         [Page 51]

RFC 1013                                                       June 1987


           Errors: Font

           Returns logical information about a font.

           The draw-direction is essentially just a hint, indicating
           whether most char-infos have a positive (LeftToRight) or a
           negative (RightToLeft)  character-width metric.  The core
           protocol defines no support for vertical text.

           If min-byte1 and max-byte1 are both zero, then
           min-char-or-byte2 specifies the linear character index
           corresponding to the first elementb of char-infos, and
           max-char-or-byte2 specifies the linear character index of
           the last element.  If either min-byte1 or max-byte1 are
           non-zero, then both min-char-or-byte2 and
           max-char-or-byte2 will be less than 256, and the two-byte
           character index values corresponding to char-infos element
           N (counting from 0) are
               byte1 = N/D + min-byte1
               byte2 = N\D + min-char-or-byte2
           where
               D = max-char-or-byte2 - min-char-or-byte2 + 1
               / = integer division
               \ = integer modulus

           If char-infos has length zero, then min-bounds and
           max-bounds will be identical, and the effective
           char-infos is one filled with this char-info, of length
               L = D * (max-byte1 - min-byte1 + 1)
           That is, all glyphs in the specified linear or matrix
           range have the same information, as given by min-bounds
           (and max-bounds). If all-chars-exist is True, then all
           characters in char-infos have non-zero bounding boxes.

           The default-char specifies the character that will be
           used when an undefined or non-existent character is used.
           Note that default-char is a CARD16 (not CHAR2B); for a
           font using two-byte matrix format, the default-char has
           byte1 in the most significant byte, and byte2 in the
           least significant byte.  If the default-char itself
           specifies an undefined or non-existent character, then
           no printing is performed for an undefined or non-existent
           character.

           The min-bounds and max-bounds contain the minimum and
           maximum values of each individual CHARINFO component over
           all char-infos (ignoring non-existent characters).  The
           bounding box of the font, i.e., the smallest rectangle
           enclosing the shape obtained  by superimposing all
           characters at the same origin [x,y], has  its upper left
           coordinate at



M.I.T.                                                         [Page 52]

RFC 1013                                                       June 1987


               [x + min-bounds.left-side-bearing, y - max-bounds.
                    ascent] with a width of
               max-bounds.right-side-bearing - min-bounds.
                    left-side-bearing and a height of
               max-bounds.ascent + max-bounds.descent

           The font-ascent is the logical extent of the font above
           the baseline, for determining line spacing.  Specific
           characters may extend beyond this.  The font-descent is
           the logical extent of the font at or below the baseline,
           for determining line spacing. Specific characters may
           extend beyond this.  If the baseline is at Y-coordinate
           y, then the logical extent of the font is inclusive
           between the Y-coordinate values (y - font-ascent) and
           (y + font-descent - 1).

           A font is not guaranteed to have any properties.  Whether
           a property value is signed or unsigned must be derived
           from a prior knowledge of the property.  When possible,
           fonts should have at least the following properties (note
           that the trailing colon is not part of the name, and that
           upper/lower case matters).

           MIN_SPACE: CARD32
              The minimum interword spacing, in pixels.
           NORM_SPACE: CARD32
               The normal interword spacing, in pixels.
           MAX_SPACE: CARD32
               The maximum interword spacing, in pixels
           SUBSCRIPT_X: INT32
           SUBSCRIPT_Y: INT32
               Offsets from the character origin where subscripts
               should begin, in pixels.  If the origin is at [x,y],
               then subscripts should begin at [x + SubscriptX,
                   y + SubscriptY].
           UNDERLINE_POSITION: INT32
               Y offset from the baseline to the top of an underline,
               in pixels. If the baseline is Y-coordinate y, then
               the top of the underline is at (y +
                    UnderlinePosition).
           UNDERLINE_THICKNESS: CARD32
               Thickness of the underline, in pixels.
           STRIKEOUT_ASCENT: INT32
           STRIKEOUT_DESCENT: INT32
               Vertical extents for boxing or voiding characters, in
               pixels.  If the baseline is at Y-coordinate y, then
               the top of the strikeout box is at (y -
               StrikeoutAscent), and the height of the box is
               (StrikeoutAscent +  StrikeoutDescent).
           ITALIC_ANGLE: INT32
               The angle of characters in the font, in degrees



M.I.T.                                                         [Page 53]

RFC 1013                                                       June 1987


               scaled by 64, relative to the three-oclock position
               from the character origin, with positive indicating
               counterclockwise motion (as in Arc requests).
           X_HEIGHT: INT32
               "1 ex" as in TeX, but expressed in units of pixels.
               Often the height of lowercase x.
           QUAD_WIDTH: INT32
               "1 em" as in TeX, but expressed in units of pixels.
               Often the width of the digits 0-9.
           WEIGHT: CARD32
               The weight or boldness of the font, expressed as a
               value between 0 and 1000.
           POINT_SIZE: CARD32
               The point size, expressed in 1/10ths, of this font at
               the ideal resolution.  There are 72.27 points to the
               inch.
           RESOLUTION: CARD32
               The number of pixels per point, expressed in 1/100ths,
               at which this font was created.

           For a character origin at [x,y], the bounding box of a
           character,i.e., the smallest rectangle enclosing the
           character's shape,  described in terms of CHARINFO
           components, is a rectangle with its upper left corner at
                   [x + left-side-bearing, y - ascent]
           with a width of
                   right-side-bearing - left-side-bearing
           and a height of
                   ascent + descent
           and the origin for the next character is defined to be
                   [x + character-width, y]
           Note that the baseline is logically viewed as being just
           below non-descending characters (when descent is zero,
           only pixels with Y-coordinates less than y are drawn),
           and that the origin is logically viewed as being
           coincident with the left edge of a non-kerned character
           (when left-side-bearing is zero, no pixels with
           X-coordinate less than x are drawn).

           Note that CHARINFO metric values can be negative.

           A non-existent character is represented with all CHARINFO
           components zero.

           The interpretation of the per-character attributes field
           is undefined by the core protocol.

QueryTextExtents
           font: FONT or GCONTEXT
           items: STRING16
       =>



M.I.T.                                                         [Page 54]

RFC 1013                                                       June 1987


           draw-direction: {LeftToRight, RightToLeft}
           font-ascent: INT16
           font-descent: INT16
           overall-ascent: INT16
           overall-descent: INT16
           overall-width: INT32
           overall-left: INT32
           overall-right: INT32

           Errors: Font

           Returns the logical extents of the specified string of
           characters in the specified font.  Draw-direction,
           font-ascent, and font-descent are as described in
           QueryFont.  Overall-ascent is the maximum of the ascent
           metrics of all characters in the string, and
           overall-descent is the maximum of the descent metrics.
           Overall-width is the sum of the character-width metrics
           of all characters in the string.  For each character in
           the string, let W be the sum of the character-width
           metrics of all characters preceding it in the string,
           let L be the left-side-bearing metric of the character
           plus W, and let R be the right-side-bearing metric of
           the character plus W.  Overall-left is the minimum L of
           all characters in the string, and overall-right is the
           maximum R.

           For fonts defined with linear indexing rather than
           two-byte matrix indexing, the server will interpret each
           CHAR2B as a 16-bit number that has been transmitted most
           significant byte first (i.e., byte1 of the CHAR2B is
           taken as the most significant byte).

           If the font has no defined default-char, then undefined
           characters in   the string are taken to have all zero
           metrics.
ListFonts
           pattern: STRING8
           max-names: CARD16
       =>
           names: LISTofSTRING8

           Returns a list of length at most max-names, of names of
           fonts matching the pattern.  The pattern should use the
           ASCII encoding, and upper/lower case does not matter.
           In the pattern, the '?' character (octal value 77) will
           match any single character, and the character '*' (octal
           value 52) will match any number of characters.  The
           returned names are in lower case.





M.I.T.                                                         [Page 55]

RFC 1013                                                       June 1987


ListFontsWithInfo
           pattern: STRING8
           max-names: CARD16
       =>
           fonts: LISTofFONTDATA

           where
                   FONTDATA: [name: STRING8
                              info: FONTINFO]
                   FONTINFO: <same type definition as in QueryFont>

           Like ListFonts, but also returns information about each
           font.  The information returned for each font is
           identical to what QueryFont would return (except that the
           per-character metrics are not returned).

SetFontPath
           path: LISTofSTRING8

           Errors: Value

           Defines the search path for font lookup.  There is only one
           search path per server, not one per client.  The
           interpretation of the strings is operating system dependent,
           but they are intended to specify directories to be
           searched in the order listed.

           Setting the path to the empty list restores the default
           path defined for the server.

           As a side-effect of executing this request, the server
           is guaranteed to flush all cached information about fonts
           for which there currently are no explicit resource ids
           allocated.

           The meaning of an error from this request is system
           specific.

GetFontPath
       =>
           path: LISTofSTRING8

           Returns the current search path for fonts.

CreatePixmap
           pid: PIXMAP
           drawable: DRAWABLE
           depth: CARD8
           width, height: CARD16

           Errors: IDChoice, Drawable, Value, Alloc



M.I.T.                                                         [Page 56]

RFC 1013                                                       June 1987


           Creates a pixmap, and assigns the identifier pid to it.
           Width and height must be non-zero.  Depth must be one of
           the depths supported by root of the specified drawable.
           The initial contents of the pixmap are undefined.

           It is legal to pass an InputOnly window as a drawable to
           this request.

FreePixmap
           pixmap: PIXMAP

           Errors: Pixmap

           Deletes the association between the resource id and the
           pixmap.  The pixmap storage will be freed when no other
           resource references it.

CreateGC
           cid: GCONTEXT
           drawable: DRAWABLE
           value-mask: BITMASK
           value-list: LISTofVALUE

           Errors: IDChoice, Drawable, Pixmap, Font, Match, Value, Alloc

           Creates a graphics context, and assigns the identifier cid to
           it.  The gcontext can be used with any destination drawable
           having the same root and depth as the specified drawable.

           The value-mask and value-list specify which components are to
           be explicitly initialized.  The context components are:

             alu-function: {Clear, And, AndReverse, Copy, AndInverted,
                            Noop, Xor, Or, Nor, Equiv, Invert,
                              OrReverse, CopyInverted, OrInverted,
                              Nand, Set}
             plane-mask: CARD32
             foreground: CARD32
             background: CARD32
             line-width: CARD16
             line-style: {Solid, OnOffDash, DoubleDash}
             cap-style: {NotLast, Butt, Round, Projecting}
             join-style: {Miter, Round, Bevel}
             fill-style: {Solid, Tiled, OpaqueStippled, Stippled}
             fill-rule: {EvenOdd, Winding}
             arc-mode: {Chord, PieSlice}
             tile: PIXMAP
             stipple: PIXMAP
             tile-stipple-x-origin: INT16
             tile-stipple-y-origin: INT16
             font: FONT



M.I.T.                                                         [Page 57]

RFC 1013                                                       June 1987


             subwindow-mode: {ClipByChildren, IncludeInferiors}
             graphics-exposures: BOOL
             clip-x-origin: INT16
             clip-y-origin: INT16
             clip-mask: PIXMAP or None
             dash-offset: CARD16
             dash-list: CARD8

           In graphics operations, given a source and destination pixel,
           the result is computed bitwise on corresponding bits of the
           pixels.  That is, a boolean operation is performed in each
           bit plane. The plane-mask restricts the operation to a subset
           of planes.  That is, the result is

           ((src FUNC dst) AND plane-mask) OR (dst AND (NOT plane-mask))

           Range checking is not performed on the values for foreground,
           background, or plane-mask; they are simply truncated to the
           appropriate number of bits.

           The meanings of the alu-functions are:

               Clear               0
               And                 src AND dst
               AndReverse          src AND (NOT dst)
               Copy                src
               AndInverted         (NOT src) AND dst
               NoOp                dst
               Xor                 src XOR dst
               Or                  src OR dst
               Nor                 (NOT src) AND (NOT dst)
               Equiv               (NOT src) XOR dst
               Invert              NOT dst
               OrReverse           src OR (NOT dst)
               CopyInverted        NOT src
               OrInverted          (NOT src) OR dst
               NAnd                (NOT src) OR (NOT dst)
               Set                 1

           Line-width is measured in pixels and can be greater than or
           equal to one (a "wide" line) or the special value zero (a
           "thin" line).

           Wide lines are drawn centered on the path described by the
           graphics request.  Unless otherwise specified by the join or
           cap style, the bounding box of a wide line with endpoints
           [x1, y1], [x2, y2], and width w is a rectangle with vertices
           at the following real coordinates:

           [x1-(w*sn/2), y1+(w*cs/2)], [x1+(w*sn/2), y1-(w*cs/2)],
           [x2-(w*sn/2), y2+(w*cs/2)], [x2+(w*sn/2), y2-(w*cs/2)]



M.I.T.                                                         [Page 58]

RFC 1013                                                       June 1987


           where sn is the sine of the angle of the line and cs is the
           cosine of the angle of the line.  A pixel is part of the line
           (and hence drawn) if the center of the pixel is fully inside
           the bounding box (which is viewed as having infinitely thin
           edges).  If the center of the pixel is exactly on the
           bounding box, it is part of the line if and only if the
           interior is immediately to its right (x increasing
           direction).  Pixels with centers on a horizontal edge are a
           special case and are part of the line if and only if the
           interior is immediately below (y increasing direction).
           Note that this description is a mathematical model
           describing the pixels that are drawn for a wide line and
           does not imply that trigonometry is required to implement
           such a model.  Real or fixed point arithmetic is
           recommended for computing the corners of the line endpoints
           for lines greater than one pixel in width.

           Thin lines (zero line-width) are "one pixel wide" lines drawn
           using an unspecified, device dependent algorithm (for
           example, Bresenham). There are only two constraints on this
           algorithm. First, if a line is drawn unclipped from [x1,y1]
           to [x2,y2] and another line is drawn unclipped from [x1+dx,
           y1+dy] to [x2+dx,y2+dy], then a point [x,y] is touched by
           drawing the first line if and only if the point [x+dx,y+dy]
           is touched by drawing the second line.  Second, the effective
           set of points comprising a line cannot be affected by
           clipping; that is, a point is touched in a clipped line if
           and only if the point lies inside the clipping region and
           the point would be touched by the line when drawn unclipped.

           Note that a wide line drawn from [x1,y1] to [x2,y2] always
           draws the same pixels as a wide line drawn from [x2,y2] to
           [x1,y1], not counting cap and join styles, but this property
           is not guaranteed for thin lines.  Also note that "jags" in
           adjacent wide lines will always line up properly, but this
           property is not guaranteed for thin lines.  A line-width of
           zero differs from a line-width of one in which pixels are
           drawn.  In general, drawing a thin line will be faster than
           drawing a wide line of width one, but thin lines may not mix
           well aesthetically desirable to obtain precise and uniform
           results across all displays, a client should always use a
           line-width of one, rather than a line-width of zero.

           The line-style defines which segments of a line are drawn:
               Solid:  the full path of the line is drawn
               DoubleDash: the full path of the line is drawn, but the
                           segments defined by the even dashes are
                           filled differently than the segments defined
                           by the odd dashes (see fill-style)
               OnOffDash: only the segments defined by the even dashes
                          are drawn, and cap-style applies to each



M.I.T.                                                         [Page 59]

RFC 1013                                                       June 1987


                          individual segment (except NotLast is treated
                          as Butt for internal caps)

           The cap-style defines how the endpoints of a path are drawn:
               NotLast: equivalent to Butt, except that for a
                        line-width of zero or one the final endpoint is
                        not drawn
               Butt: square at the endpoint, with no projection beyond
               Round: a circular arc with diameter equal to the
                      line-width, centered on the endpoint; equivalent
                      to Butt for line-width zero or one
               Projecting: square at the end, but the path continues
                           beyond the endpoint for a distance equal to
                           half the line-width; equivalent to Butt for
                           line-width zero or one

           The join-style defines how corners are drawn for wide lines:
               Miter: the outer edges of the two lines extend to meet at
                      an angle
               Round: a circular arc with diameter equal to the
                      line-width, centered on the joinpoint
               Bevel: Butt endpoint styles, and then the triangular
                      "notch" filled

           The tile/stipple and clip origins are interpreted relative to
           the origin of whatever destination drawable is specified in a
           graphics request.

           The tile pixmap must have the same root and depth as the
           gcontext (else a Match error).  The stipple pixmap must have
           depth one, and must have the same root as the gcontext (else
           a Match error).  For stipple operations, the stipple pattern
           is tiled in a  single plane, and acts as an additional clip
           mask to be ANDed with the clip-mask.  Any size pixmap can be
           used for tiling or stippling, although some sizes may be
           faster to use than others.

           The fill-style defines the contents of the source for line,
           text, and fill requests.  For all text and fill requests
           (PolyText8, PolyText16, PolyFillRectangle, FillPoly,
           PolyFillArc), for line  requests (PolyLine, PolySegment,
           PolyRectangle, PolyArc) with line-style Solid, and for the
           even dashes for line requests with line-style OnOffDash or
           DoubleDash:
               Solid: foreground
               Tiled: tile
               OpaqueStippled: a tile with the same width and height as
                               stipple, but with background everywhere
                               stipple has a zero and with foreground
                               everywhere stipple has a one
               Stippled: foreground masked by stipple



M.I.T.                                                         [Page 60]

RFC 1013                                                       June 1987


           For the odd dashes for line requests with line-style
           DoubleDash:
               Solid: background
               Tiled: same as for even dashes
               OpaqueStippled: same as for even dashes
               Stippled: background masked by stipple

           The dash-list value allowed here is actually a simplified
           form of the more general patterns that can be set with
           SetDashes.Specifying a value of N here is equivalent to
           specifying the two element list [N, N] in SetDashes.  The
           value must be non-zero.  The meaning of dash-offset and
           dash-list are explained in the SetDashes request.

           The clip-mask restricts writes to the destination drawable;
           only pixels where the clip-mask has a one bit are drawn.  It
           affects all graphics requests.  The clip-mask does not clip
           sources.  The clip-mask origin is interpreted relative to the
           origin of whatever destination drawable is specified in a
           graphics request.  If a pixmap is specified as the clip-mask,
           it must have depth one and have the same root as the gcontext
           (else a Match error).  The clip-mask can also be set with the
           SetClipRectangles request.

           For ClipByChildren, both source and destination windows are
           additionally clipped by all viewable InputOutput children.
           For IncludeInferiors, neither source nor destination window
           is clipped by inferiors; this will result in drawing through
           subwindow boundaries. The use of IncludeInferiors on a window
           of one depth with mapped inferiors of differing depth is not
           illegal, but the semantics isundefined by the core protocol.

           The fill-rule defines what pixels are inside (i.e., are
           drawn) for paths given in FillPoly requests.  EvenOdd means
           a point is inside if an infinite ray with the point as origin
           crosses the path an odd number of times.  For Winding, a
           point is inside if an infinite ray with the point as origin
           crosses an unequal number of clockwise and counterclockwise
           directed path segments.  For both rules, a "point" is
           infinitely small, and the path is an infinitely thin line.
           A pixel is inside if the center point of the pixel is inside
           and the center point is not on the boundary.  If the center
           point is on the boundary, the pixel is inside if and only if
           the polygon interior is immediately to its right (x
           increasing direction).  Pixels with centers along a
           horizontal edge are a special case and are inside if and
           only if the polygon interior is immediately below (y
           increasing direction).

           The arc-mode controls filling in the PolyFillArc request.




M.I.T.                                                         [Page 61]

RFC 1013                                                       June 1987


           The graphics-exposures flag controls GraphicsExposure event
           generation for CopyArea and CopyPlane requests (and any
           similar requests defined by extensions).

           The default component values are:
               function: Copy
               plane-mask: all ones
               foreground: 0
               background: 1
               line-width: 0
               line-style: Solid
               cap-style: Butt
               join-style: Miter
               fill-style: Solid
               full-rule: EvenOdd
               arc-mode: PieSlice
               tile: pixmap of unspecified size filled with forground
                     pixell (i.e., client specified pixel if any,
                     else 0)
               stipple: pixmap of unspecified size filled with ones
               tile-stipple-x-origin: 0
               tile-stipple-y-origin: 0
               font: <implementation dependent>
               subwindow-mode: ClipByChildren
               graphics-exposures: True
               clip-x-origin: 0
               clip-y-origin: 0
               clip-mask: None
               dash-offset: 0
               dash-list: 4 (i.e., the list [4, 4])

           Storing a pixmap in a gcontext might or might not result in a
           copy being made.  If the pixmap is later used as the
           destination for a graphics request, the change might or might
           not be reflected in the gcontext.  If the pixmap is used
           simultaneously  in a graphics request as both a destination
           and as a tile or stipple. the results are not defined.

           It is quite likely that some amount of gcontext information
           will be cached in display hardware, and that such hardware
           can only cache a small number of gcontexts.  Given the number
           and complexity of components, clients should view switching
           between gcontexts with nearly identical state as
           significantly more expensive than making minor changes to a
           single gcontext.

ChangeGC
           gc: GCONTEXT
           value-mask: BITMASK
           value-list: LISTofVALUE




M.I.T.                                                         [Page 62]

RFC 1013                                                       June 1987


           Errors: GContext, Pixmap, Font, Match, Value, Alloc

           Changes components in gc.  The value-mask and value-list
           specify which components are to be changed.  The values and
           restrictions are the same as for CreateGC.

           Changing the clip-mask also overrides any previous
           SetClipRectangles request on the context.  Changing the
           dash-offset or dash-list overrides any previous SetDashes
           request on the context.

           The order in which components are verified and altered is
           server dependent.  If an error is generated, a subset of the
           components may have been altered.

CopyGC
           src-gc, dst-gc: GCONTEXT
           value-mask: BITMASK

           Errors: GContext, Value, Match, Alloc

           Copies components from src-gc to dst-gc.  The value-mask
           specifies which components to copy, as for CreateGC.  The
           two gcontexts must have the same root and the same depth
           (else a Match error).

SetDashes
           gc: GCONTEXT
           dash-offset: CARD16
           dash-list: LISTofCARD8

           Errors: GContext, Value, Alloc

           Sets the dash-offset and dash-list in gc for dashed line
           styles.  The initial and alternating elements of the
           dash-list are the "even" dashes, the others are the
           "odd" dashes.  All of the elements must be non-zero.
           The dash-offset defines the phase of the pattern,
           specifying how many pixels into the dash-list the pattern
           should actually begin in any single graphics request.
           Dashing is continuous through path segments combined with
           a join-style, but is reset to the dash-offset each time a
           cap-style is applied.

SetClipRectangles
           gc: GCONTEXT
           clip-x-origin, clip-y-origin: INT16
           rectangles: LISTofRECTANGLE
           ordering: {UnSorted, YSorted, YXSorted, YXBanded}

           Errors: GContext, Value, Alloc, Match



M.I.T.                                                         [Page 63]

RFC 1013                                                       June 1987


           Changes clip-mask in gc to the specified list of rectangles
           and sets the clip origin.  Output will be clipped to remain
           contained within the rectangles.  The clip origin is
           interpreted relative to the origin of whatever destination
           drawable is specified in a graphics request.  The rectangle
           coordinates are interpreted relative to the clip origin.
           The rectangles should be non-intersecting, or graphics
           results will be undefined.

           If known by the client, ordering relations on the rectangles
           can be specified with the ordering argument; this may provide
           faster operation by the server.  If an incorrect ordering is
           specified, the server may generate a Match error, but is not
           required to do so; if no error is generated, the graphics
           results are undefined. UnSorted means the rectangles are in
           arbitrary order.  YSorted means that the rectangles are
           non-decreasing in their Y origin. YXSorted additionally
           constrains YSorted order in that all rectangles with an equal
           Y origin are non-decreasing in their X origin.  YXBanded
           additionally constrains YXSorted by requiring that for every
           possible Y scanline, all rectangles that include that
           scanline have identical Y origins and Y extents.

FreeGC
           gc: GCONTEXT

           Errors: GContext

           Deletes the association between the resource id and the
           gcontext, and destroys the gcontext.

ClearToBackground
           window: WINDOW
           x, y: INT16
           width, height: CARD16
           exposures: BOOL

           Errors: Window, Value, Match

           The x and y coordinates are relative to the window's origin,
           and specify the upper left corner of the rectangle.  If width
           is zero, it is replaced with the current width of the window
           minus x.  If height is zero, it is replaced with the current
           height of the window minus y.  If the window has a defined
           background tile, the rectangle is tiled with a plane-mask of
           all ones and alu-function of Copy.  If the window has
           background None, the contents of the window are not changed.
           In eithercase, if  exposures is True, then one or more
           exposure events are generated for regions of the rectangle
           that are eithervisible or are being retained in a backing
           store.



M.I.T.                                                         [Page 64]

RFC 1013                                                       June 1987


           It is a Match error to use an InputOnly window in this
           request.
CopyArea
           src-drawable, dst-drawable: DRAWABLE
           gc: GCONTEXT
           src-x, src-y: INT16
           width, height: CARD16
           dst-x, dst-y: INT16

           Errors: Drawable, GContext, Match

           Combines the specified rectangle of src-drawable with the
           specified rectangle of dst-drawable.  The src-x and src-y
           coordinates are relative to src-drawable's origin, dst-x and
           dst-y are relative to dst-drawable's origin, each pair
           specifying the  upper left corner of the rectangle.
           Src-drawable must have the same root and the same depth as
           dst-drawable (else a Match error).

           If regions of the source rectangle are obscured and have not
           been retained by the server, or if regions outside the
           boundaries of the source drawable are specified, then the
           following occurs.  If the dst-drawable is a window with a
           background of other than  None, the corresponding regions of
           the destination are tiled (with plane-mask of ones and
           alu-function Copy) with that background.  Regardless, if
           graphics-exposures in gc is True, GraphicsExposure events
           for the corresponding desitnation regions are generated.

           If graphics-exposures if True but no regions are exposed,
           then a NoExposure event is generated.

           GC components: alu-function, plane-mask, foreground,
           subwindow-mode, clip-x-origin, clip-y-origin, clip-mask

CopyPlane
           scr-drawable, dst-drawable: DRAWABLE
           GC:Gcontext
           src-x, src-y: INT16
           width, height: CARD16
           dst-x, dst-y: INT16
           bit-plane: CARD32

           Errors: Drawable, GContext, Value, Match

           Src-drawable must have the same root as dst-srawable (else
           a match error), but need not have the same depth.
           Bit-plane must have exactly one bit set.  Effectively, that
           plane of the src-drawable and the fore-ground/background
           pixels in gc are combined to form a pixmap of the same
           depth as dst-drawable, and the equivalent of a CopyArea is



M.I.T.                                                         [Page 65]

RFC 1013                                                       June 1987


           performed, with all the same exposure semantics.

           GC components: alu-function, plan-mask, foreground,
           background, subwindow-mode, graphics-exposures,
           clip-x-origin, clip-y-origin, clip-mask

PolyPoint
           drawable: DRAWABLE
           gc: GCONTEXT
           coordinate-mode: {Origin, Previous}
           points: LISTofPOINT

           Errors: Drawable, GContext, Value, Match

           Combines the foreground pixel in gc with the pixel at each
           point in the drawable.  The points are drawn in the order
           listed.

           The first point is always relative to the drawable's origin;
           the rest are relative either to that origin or the previous
           point, depending on the coordinate-mode.

           GCcomponents: alu-function, plane-mask, foreground,
           subwindow-mode, clip-x-origin, clip-y-origin, clip-mask

PolyLine
           drawable: DRAWABLE
           gc: GCONTEXT
           coordinate-mode: {Origin, Previous}
           points: LISTofPOINT

           Errors: Drawable, GContext, Value, Match

           Draws lines between each pair of points (point[i], point
           [i+1]). The lines are drawn in the order listed.  The lines
           join correctly at all intermediate points, and if the first
           and last points coincide, the first and last lines also join
           correctly.

           For any given line, no pixel is drawn more than once.  If
           thin (zero line-width) lines intersect, the intersecting
           pixels are drawn multiple times.  If wide lines intersect,
           the intersecting pixels are drawn only once, as though the
           entire PolyLine were a single filled shape.

           The first point is always relative to the drawable's origin;
           the rest are relative either to that origin or the previous
           point,  depending on the coordinate-mode.

           GC components: alu-function, plane-mask, line-width,
           line-style, cap-style, join-style, fill-style,



M.I.T.                                                         [Page 66]

RFC 1013                                                       June 1987


           subwindow-mode, clip-x-origin, clip-y-origin, clip-mask

           GC mode-dependent components: foreground, background, tile,
           stipple, tile-stipple-x-origin, tile-stipple-y-origin,
           dash-offset,dash-list

PolySegment
           drawable: DRAWABLE
           gc: GCONTEXT
           segments: LISTofSEGMENT

           where SEGMENT: [x1, y1, x2, y2: INT16]

           Errors: Drawable, GContext, Match

           For each segment, draws a line between [x1, y1] and [x2, y2].
           The lines are drawn in the order listed.  No joining is
           performed at coincident end points.  For any given line, no
           pixel is drawn more than once.  If lines intersect, the
           intersecting pixels are drawn multiple times.

           GC components: alu-function, plane-mask, line-width,
           line-style, cap-style, fill-style, subwindow-mode,
           clip-x-origin, clip-y-origin,clip-mask

           GC mode-dependent components: foreground, background, tile,
           stipple,tile-stipple-x-origin, tile-stipple-y-origin,
           dash-offset, dash-list

PolyRectangle
           drawable: DRAWABLE
           gc: GCONTEXT
           rectangles: LISTofRECTANGLE

           Errors: Drawable, GContext, Match

           Draws the outlines of the specified rectangles, as if a
           five-point PolyLine were specified for each rectangle.  The x
           and y coordinates of each rectangle are relative to the
           drawable's origin, and define the upper left corner of the
           rectangle.

           The rectangles are drawn in the order listed.  For any given
           rectangle, no pixel is drawn more than once.  If rectangles
           intersect, the intersecting pixels are drawn multiple times.

           GC components: alu-function, plane-mask, line-width,
           line-style, join-style, fill-style, subwindow-mode,
           clip-x-origin, clip-y-origin, clip-mask

           GC mode-dependent components: foreground, background, tile,



M.I.T.                                                         [Page 67]

RFC 1013                                                       June 1987


           stipple, tile-stipple-x-origin, tile-stipple-y-origin,
           dash-offset, dash-list

PolyArc
           drawable: DRAWABLE
           gc: GCONTEXT
           arcs: LISTofARC

           Errors: Drawable, GContext, Match

           Draws circular or elliptical arcs.  Each arc is specified by
           a rectangle and two angles.  The x and y coordinates are
           relative to the origin of the drawable, and define the upper
           left corner of the rectangle.  The center of the circle or
           ellipse is the center of the rectangle, and the major and
           minor axes are specified by the width and height,
           respectively.  The angles are signed integers in degrees
           scaled by 64, with positive indicating counterclockwise
           motion and negative indicating clockwise motion.  The start
           of the arc is specified by angle1 relative to the
           three-oclock position from the center, and the path and
           extent of the arc is specified by angle2 relative to the
           start of the arc.  If the magnitude of angle2 is greater
           than 360 degrees, it is truncated to 360 degrees.

           The arcs are drawn in the order listed.  If the last point in
           one arc coincides with the first point in the following arc,
           the two arcs will join correctly.  If the first point in the
           first arc coincides with the last point in the last arc, the
           two arcs will join correctly.  For any given arc, no pixel is
           drawn more than once.  If two arcs join correctly and the
           line-width is greater than zero and the arcs intersect, no
           pixel is drawn more than once.  Otherwise, the intersecting
           pixels of intersecting arcs are drawn multiple times.
           Specifying an arc with one endpoint and a clockwise extent
           draws the same pixels as specifying the other endpoint and an
           equivalent counterclockwise extent, except as it affects
           joins.

           By specifying one axis to be zero, a horizontal or vertical
           line can be drawn.

           Angles are computed based solely on the coordinate system,
           ignoring the aspect ratio.

           GC components: alu-function, plane-mask, line-width,
           line-style, cap-style, join-style, fill-style,
           subwindow-mode, clip-x-origin, clip-y-origin, clip-mask

           GC mode-dependent components: foreground, background, tile,
           stipple,tile-stipple-x-origin, tile-stipple-y-origin,



M.I.T.                                                         [Page 68]

RFC 1013                                                       June 1987


           dash-offset, dash-list
FillPoly
           drawable: DRAWABLE
           gc: GCONTEXT
           shape: {Complex, Nonconvex, Convex}
           coordinate-mode: {Origin, Previous}
           points: LISTofPOINT

           Errors: Drawable, GContext, Match, Value

           Fills the region closed by the specified path.  The path is
           closed automatically if the last point in the list does not
           coincide with the first point.  No pixel of the region is
           drawn more than once.

           The first point is always relative to the drawable's origin;
           the rest are relative either to that origin or the previous
           point, depending on the coordinate-mode.

           The shape parameter may be used by the server to improve
           performance. Complex means the path may self-intersect.

           Nonconvex means the path does not self-intersect, but the
           shape is not wholly convex.  If known by the client,
           specifying Nonconvex over Complex may improve performance. If
           Nonconvex is specified for a self-intersecting path, the
           graphics results are undefined.

           Convex means the path is wholly convex. If known by the
           client, specifying Convex can improve performance.  If Convex
           is specified for a path that is not convex, the graphics
           results are undefined.

           GC components: alu-function, plane-mask, fill-style,
           fill-rule, subwindow-mode, clip-x-origin, clip-y-origin,
           clip-mask

           GC mode-dependent components: foreground, tile, stipple,
           tile-stipple-x-origin, tile-stipple-y-origin

PolyFillRectangle
           drawable: DRAWABLE
           gc: GCONTEXT
           rectangles: LISTofRECTANGLE

           Errors: Drawable, GContext, Match

           Fills the specified rectangles.  The x and y coordinates of
           each rectangle are relative to the drawable's origin, and
           define the upper left corner of the rectangle.




M.I.T.                                                         [Page 69]

RFC 1013                                                       June 1987


           The rectangles are drawn in the order listed.  For any given
           rectangle, no pixel is drawn more than once.  If rectangles
           intersect, the intersecting pixels are drawn multiple times.

           GC components: alu-function, plane-mask, fill-style,
           fill-rule, subwindow-mode, clip-x-origin, clip-y-origin,
           clip-mask

           GC mode-dependent components: foreground, tile, stipple,
           tile-stipple-x-origin, tile-stipple-y-origin

PolyFillArc
           drawable: DRAWABLE
           gc: GCONTEXT
           arcs: LISTofARC

           Errors: Drawable, GContext, Match

           For each arc, fills the region closed by the specified arc
           and one or two line segments, depending on the arc-mode.  For
           Chord, the single line segment joining the endpoints of the
           arc is used.  For PieSlice, the two line segments joining the
           endpoints of the arc with the center point are used.  The
           arcs are as specified in the PolyArc request.

           The arcs are filled in the order listed.  For any given arc,
           no pixel is drawn more than once.  If regions intersect, the
           intersecting pixels are drawn multiple times.

           GC components: alu-function, plane-mask, fill-style,
           fill-rule, arc-mode, subwindow-mode, clip-x-origin,
           clip-y-origin, clip-mask

           GC mode-dependent components: foreground, tile, stipple,
           tile-stipple-x-origin, tile-stipple-y-origin

PutImage
           drawable: DRAWABLE
           gc: GCONTEXT
           depth: CARD8
           width, height: CARD16
           dst-x, dst-y: INT16
           left-pad: CARD8
           format: {Bitmap, XYPixmap, ZPixmap}
           bits: <bits>

           Errors: Drawable, GContext, Match, Value, Alloc

           Combines an image with a rectangle of the drawable.  The
           dst-x and dst-y coordinates are relative to the drawable's
           origin.



M.I.T.                                                         [Page 70]

RFC 1013                                                       June 1987


           If Bitmap format is used, then depth must be one (else a
           Match error) and the image must be in XYFormat. The
           foreground pixel in gc defines the source for one bits in the
           image, and the background pixel defines the source for the
           zero bits.

           For XYPixmap and ZPixmap, depth must match the depth of
           drawable (else a Match error).  For XYPixmap, the image must
           be sent in XYFormat.  For ZPixmap, the image must be sent in
           the ZFormat defined for the given depth.

           The left-pad must be zero for ZPixmap format.  For Bitmap and
           XYPixmap format, left-pad must be less than
           bitmap-format-scanline-pad (as given in the server connection
           setup info).  The first left-pad bits in every scanline are
           to be ignored by the server; the actual image begins that
           many bits into the data.  The width argument defines the width
           of the actual image, and does not include left-pad.

           GC components: alu-function, plane-mask, subwindow-mode,
           clip-x-origin, clip-y-origin, clip-mask

           GC mode-dependent components: foreground, background

GetImage
           drawable: DRAWABLE
           x, y: INT16
           width, height: CARD16
           plane-mask: CARD32
           format: {XYFormat, ZFormat}
       =>
           depth: CARD8
           visual: VISUALID or None
           bits: <bits>

           Errors: Drawable, Value, Match

           Returns the contents of the given rectangle of the drawable
           in the given format.  The x and y coordinates are relative to
           the drawable's origin, and define the upper left corner of
           the rectangle. If XYFormat is specified, only the bit planes
           specified in plane-mask are transmitted.  If ZFormat is
           specified, then bits in all planes not specified in
           plane-mask transmitted as zero.  The returned depth specifies
           the number of bits per pixel of the image.  If the drawable
           is a window,  its visual type is returned; if the drawable
           is a pixmap,the visual is None.

           If the drawable is a window, the window must be mapped, and
           it must be the case that, if there were no inferiors or
           overlapping windows, the specified rectangle of the window



M.I.T.                                                         [Page 71]

RFC 1013                                                       June 1987


           would be fully visible on the screen will include any
           visible portions of inferiors or overlapping windows
           contained in the rectangle, but if these windows are of
           different depth than the specified window, the contents
           returned for them are not defined by the core protocol.
PolyText8
           drawable: DRAWABLE
           gc: GCONTEXT
           x, y: INT16
           items: LISTofTEXTITEM8

           where
                   TEXTITEM8: TEXTELT8 or FONT
                   TEXTELT8: [delta: INT8
                              string: STRING8]

           Errors: Drawable, GContext, Match, Font

           The x and y coordinates are relative to drawable's origin,
           and specify the baseline starting position (the initial
           character origin). Each text item is processed in turn.  A
           font item causes the font to be stored in gc, and to be
           used for subsequent text; switching among fonts with
           differing draw-directions is permitted.  A text element
           delta specifies an additional change in the position along
           the x axis before the string is drawn; the delta is always
           added to the character origin (not added or subtracted based
           on the draw-direction of the current font).  Each character
           image, as defined by the a font in gc, is treated as an
           additional mask for a fill operation on the drawable.

           All contained FONTs are always transmitted most significant
           byte first.

           If a Font error is generated for an item, the previous items
           may have been drawn.

           For fonts defined with two-byte matrix indexing, each STRING8
           byte is interpreted as a byte2 value of a CHAR2B with a byte1
           value of zero.

           GC components: alu-function, plane-mask, fill-style, font,
           subwindow-mode, clip-x-origin, clip-y-origin, clip-mask

           GC mode-dependent components: foreground, tile, stipple,
           tile-stipple-x-origin, tile-stipple-y-origin

PolyText16
           drawable: DRAWABLE
           gc: GCONTEXT
           x, y: INT16



M.I.T.                                                         [Page 72]

RFC 1013                                                       June 1987


           items: LISTofTEXTITEM16

           where
                   TEXTITEM16: TEXTELT16 or FONT
                   TEXTELT16: [delta-x: INT8
                               string: STRING16]

           Errors: Drawable, GContext, Match, Font

           Just like PolyText8, except two-byte (or 16-bit) characters
           are used. For fonts defined with linear indexing rather than
           two-byte matrix indexing, the server will interpret each
           CHAR2B as a 16-bit number that has been transmitted most
           significant byte first (i.e., byte1 of the CHAR2B is taken
           as the most significant byte).

ImageText8
           drawable: DRAWABLE
           gc: GCONTEXT
           x, y: INT16
           string: STRING8

           Errors: Drawable, GContext, Match

           The x and y coordinates are relative to drawable's origin,
           and specify the baseline starting position (the initial
           character origin). The effect is to first fill a
           destination rectangle with the background pixel defined in
           gc, and then paint the text with the foreground pixel.
           The upper left corner of the filled rectangle is at
                   [x + overall-left, y - font-ascent]
           the width is
                   overall-right - overall-left
           and the height is
                   font-ascent + font-descent
           where overall-left, overall-right, font-ascent, and
           as font-descent are would be returned by a QueryTextExtents
           call using gc and string.

           The alu-function and fill-style defined in gc are ignored for
           this request; the effective alu-function is Copy and the
           effective fill-style Solid.

           For fonts defined with two-byte matrix indexing, each STRING8
           byte is interpreted as a byte2 value of a CHAR2B with a byte1
           value of zero.

           GC components: plane-mask, foreground, background, font,
           subwindow-mode, clip-x-origin, clip-y-origin, clip-mask





M.I.T.                                                         [Page 73]

RFC 1013                                                       June 1987


ImageText16
           drawable: DRAWABLE
           gc: GCONTEXT
           x, y: INT16
           string: STRING16

           Errors: Drawable, GContext, Match

           Just like ImageText8, except two-byte (or 16-bit) characters
           are used. For fonts defined with linear indexing rather than
           two-byte matrix indexing, the server will interpret each
           CHAR2B as a 16-bit number that has been transmitted most
           significant byte first (i.e., byte1 of the CHAR2B is taken as
           the most significant byte).

CreateColormap
           mid: COLORMAP
           visual: VISUALID
           window: WINDOW
           alloc: {None, All}

           Errors: IDChoice, Window, Value, Match, Alloc

           Creates a colormap of the specified visual type for the
           screen on which the window resides, and associates the
           identifier mid with it.  The visual type must be one
           supported by the screen, and cannot be of class TrueColor
           (else a Match error).  The initial values of the colormap
           entries are undefined for classes GrayScale, PseudoColor,
           and DirectColor; for StaticGray, StaticColor, and
           TrueColor, the entries will have defined values, but those
           values are specific to the visual and are not defined by
           the core protocol.  For StaticGray, StaticColor, and
           TrueColor, alloc must be specified as None (else a Match
           error). For the other classes, if alloc is None, the
           colormap initially has no allocated entries, and clients
           can allocate entries.  If alloc is All, then the entire
           colormap is "allocated" writable, but entries cannot be
           freed with FreeColors, and no relationships among entries
           is defined; the client must understand whether the colormap
           is GrayScale, PseudoColor, or DirectColor to know how to
           store into entries.

FreeColormap
           cmap: COLORMAP

           Errors: Colormap

           Deletes the association between the resource id and the
           colormap.  If the colormap is an installed map for a screen,
           it is uninstalled (see UninstallColormap).  If the colormap



M.I.T.                                                         [Page 74]

RFC 1013                                                       June 1987


           is defined as the colormap for a window (via CreateWindow or
           ChangeWindowAttributes), the colormap for the window is
           changed to None, and a ColormapNotify event is generated.The
           colors displayed for a window with a colormap of None are not
           defined by the protocol.

           Has no effect on a default colormap for a screen.


CopyColormapAndFree
           mid, src-cmap: COLORMAP

           Errors: Colormap, Alloc

           Creates a colormap for the same screen as src-cmap, and
           associates identifier mid with it.  Moves all of the client's
           existing allocations from src-cmap to the new colormap, and
           frees those entries in src-cmap. Values in other entries in
           the new colormap are undefined.

InstallColormap
           cmap: COLORMAP

           Errors: Colormap

           Makes this colormap an installed map for its screen.  All
           windows associated with this colormap immediately display
           with true colors.  As a side-effect, previously installed
           colormaps may be uninstalled, and other windows may display
           with false colors.  Which colormaps get uninstalled is
           server dependent, except that it is guaranteed that the
           M-1 most recently client-installed colormaps will not be
           uninstalled, where M is the min-installed-maps specified
           for the screen in the connection setup.

           If cmap is not already an installed map, a ColormapNotify
           event is generated on every window having cmap as an
           attribute.  If a colormap is uninstalled as a result of
           the install, a ColormapNotify event is generated on every
           window having that colormap as an attribute.

           Initially only the default colormap for a screen is
           installed.

UninstallColormap
           cmap: COLORMAP

           Errors: Colormap

           If cmap is an installed map for its screen, one or more
           colormaps are installed in its place; the choice is server



M.I.T.                                                         [Page 75]

RFC 1013                                                       June 1987


           dependent, pexcept that if the screen's default colormap is
           not installed and can be installed (without forcing other
           colormaps out), then the default colormap is used.

           If cmap is an installed map, a ColormapNotify event is
           generated on every window having this colormap as an
           attribute.  If a colormap is installed as a result of the
           uninstall, a ColormapNotify event is generated on every
           window having that colormap as an attribute.

ListInstalledColormaps
           window: WINDOW
       =>
           cmaps: LISTofCOLORMAP

           Errors: Window

           Returns a list of the currently installed colormaps for the
           screen of the specified window.

AllocColor
           cmap: COLORMAP
           red, green, blue: CARD16
       =>
           pixel: CARD32
           red, green, blue: CARD16

           Errors: Colormap, Alloc

           Allocates a read-only colormap entry corresponding to the
           closest RGB values provided by the hardware.  Returns the
           pixel and the RGB values actually used.

AllocNamedColor
           cmap: COLORMAP
           name: STRING8
       =>
           pixel: CARD32
           exact-red, exact-green, exact-blue: CARD16
           screen-red, screen-green, screen-blue: CARD16

           Errors: Colormap, Name, Alloc

           Looks up the named color with respect to the screen
           associated with the colormap, then does an AllocColor on
           cmap.  The name should use the  ASCII encoding, and
           upper/lower case does not matter. The exact RGB values
           specify the "true" values for the color, and the screen
           values specify the values actually used in the colormap.





M.I.T.                                                         [Page 76]

RFC 1013                                                       June 1987


AllocColorCells
           cmap: COLORMAP
           colors, planes: CARD16
           contiguous: BOOL
       =>
           pixels, masks: LISTofCARD32

           Errors: Colormap, Value, Alloc

           The number of colors must be positive, the number of planes
           non-negative.  If C colors and P planes are requested, then C
           pixels  and P masks are returned.  No mask will have any bits
           in common with any other mask, or with any of the pixels.  By
           ORing together masks and pixels, C*(2^P) distinct pixels can
           be produced; all of these are allocated writable by the
           request.  For GrayScale or PseudoColor, each mask will have
           exactly one bit, and for DirectColor each will have exactly
           three bits.   If contiguous is True, then if all masks are
           ORed together, a single contiguous set of bits will be formed
           for GrayScale or PseudoColor, and three contiguous sets of
           bits (one within each pixel subfield) for DirectColor.  The
           RGB values of the allocated entries are undefined.

AllocColorPlanes
           cmap: COLORMAP
           colors, reds, greens, blues: CARD16
           contiguous: BOOL
       =>
           pixels: LISTofCARD32
           red-mask, green-mask, blue-mask: CARD32

           Errors; Colormap, Value, Alloc

           The number of colors must be positive, the reds, greens, and
           blues non-negative.  If C colors, R reds, G greens, and B
           blues are requested, then C pixels are returned, and the
           masks have R, G, and B bits set respectively.  If contiguous
           is True, then each mask will have a contiguous set of bits.
           No mask will have any bits in common with any other mask, or
           with any of the pixels.  For DirectColor, each mask will lie
           within the corresponding pixel subfield.  By ORing together
           subsets of masks with pixels, C*(2^(R+G+B)) distinct pixels
           can be produced; all of these are allocated by the request.
           The initial RGB values of the allocated entries are
           undefined. In the colormap there are only C*(2^R)
           independent red entries, C*(2^G) independent green entries,
           and C*(2^B) independent blue entries.  This is true even for
           PseudoColor.  When the colormap entry for a pixel value is
           changed using StoreColors or StoreNamedColor, the pixel is
           decomposed according to the masks and the corresponding
           independent entries are updated.



M.I.T.                                                         [Page 77]

RFC 1013                                                       June 1987


FreeColors
           cmap: COLORMAP
           pixels: LISTofCARD32
           plane-mask: CARD32

           Errors: Colormap, Access, Value

           The plane-mask should not have any bits in common with any of
           the pixels.  The set of all pixels is produced by ORing
           together subsets of plane-mask with the pixels.  The request
           frees all of these pixels. Note that freeing an individual
           pixel obtained from AllocColorPlanes may not actually allow
           it to be reused until all of its "related" pixels are also
           freed.

           All specified pixels that are allocated by the client in
           cmap are freed, even if one or more pixels produce an error.
           A Value error is generated if a specified pixel is not a
           valid index into cmap, and an Access error is generated if a
           specified pixel is not allocated by the client (i.e., is
           unallocated or is only allocated by another client). If more
           than one pixel is in error, which one is reported is
           arbitrary.

StoreColors
           cmap: COLORMAP
           items: LISTofCOLORITEM

           where
                   COLORITEM: [pixel: CARD32
                               do-red, do-green, do-blue: BOOL
                               red, green, blue: CARD16]

           Errors: Colormap, Access, Value

           Changes the colormap entries of the specified pixels.  The
           do-red, do-green, and do-blue fields indicate which
           components should actually be changed.  If the colormap is an
           installed  map for its screen, the changes are visible
           immediately.

           All specified pixels that are allocated writable in cmap (by
           any client) are changed, even if one or more pixels produce
           an error.  A Value error is generated if a specified pixel is
           not a valid index into cmap, and an Access error is generated
           if a specified pixel is unallocated or is allocated
           read-only.  If more than one pixel is in error, which one is
           reported is arbitrary.

StoreNamedColor
           cmap: COLORMAP



M.I.T.                                                         [Page 78]

RFC 1013                                                       June 1987


           pixel: CARD32
           name: STRING8
           do-red, do-green, do-blue: BOOL

           Errors: Colormap, Name, Access, Value

           Looks up the named color with respect to the screen
           associated with cmap, then does a StoreColors in cmap.  The
           name should use the ASCII encoding, and upper/lower case
           does not matter.

QueryColors
           cmap: COLORMAP
           pixels: LISTofCARD32
       =>
           colors: LISTofRGB

           where
                   RGB: [red, green, blue: CARD16]

           Errors: Colormap, Value

           Returns the color values stored in cmap for the specified
           pixels.  The values returned for an unallocated entry are
           undefined. A Value error is generated if a pixel is not a
           valid index into cmap.  If more than one pixel is in error,
           which one is reported is arbitrary.

LookupColor
           cmap: COLORMAP
           name: STRING8
       =>
           exact-red, exact-green, exact-blue: CARD16
           screen-red, screen-green, screen-blue: CARD16

           Errors: Colormap, Name

           Looks up the string name of a color with respect to the
           screen associated with cmap, and returns both the exact the
           color values and the closest values provided by the hardware.
           The name should use the ASCII encoding, and upper/lower
           case does not matter.

CreateCursor
           cid: CURSOR
           source: PIXMAP
           mask: PIXMAP or None
           fore-red, fore-green, fore-blue: CARD16
           back-red, back-green, back-blue: CARD16
           x, y: CARD16




M.I.T.                                                         [Page 79]

RFC 1013                                                       June 1987


           Errors: IDChoice, Bitmap, Match, Value, Alloc

           Creates a cursor and associates identifier cid with it.
           Foreground and background RGB values must be specified, even
           if the server only has a monochrome screen.  The foreground
           is used for the one bits in the source, and the background is
           used for the zero bits.  Both source and mask (if specified)
           must have depth one (else a Match error), but can have any
           root.  The mask pixmap defines the shape of the cursor; that
           is, the one bits in the mask define which source pixels will
           be displayed.  If no mask is given, all pixels of the source
           are displayed.  The mask, if present, must be the same size
           as source (else a Match error).  The x and y coordinates
           define the hotspot, relative to the source's origin, and must
           be a point within the source (else a Match error).

           The components of the cursor may be transformed arbitrarily
           to meet display limitations.

           The pixmaps can be freed immediately if no further explicit
           references to them are to be made.

           Subsequent drawing in the source or mask pixmap has an
           undefined effect on the cursor; the server might or might
           not make a copy of the pixmap.

CreateGlyphCursor
           cid: CURSOR
           source-font: FONT
           mask-font: FONT or None
           source-char, mask-char: CARD16
           fore-red, fore-green, fore-blue: CARD16
           back-red, back-green, back-blue: CARD16

           Errors: IDChoice, Font, Value, Alloc

           Similar to CreateCursor, but the source and mask bitmaps are
           obtained from the specified font glyphs.  The mask font and
           character are optional.  The origin of the source glyph
           defines the hotspot, and the mask is positioned such that
           the origins are coincident.  The source and mask need not
           have the same bounding box metrics.  If no mask is given,
           all pixels of the source are displayed.  Note that
           source-char and mask-char are CARD16 (not CHAR2B); for
           two-byte matrix fonts, the 16-bit value should be formed
           with byte1 in the most significant byte and byte2 in the
           least significant byte.

FreeCursor
           cursor: CURSOR




M.I.T.                                                         [Page 80]

RFC 1013                                                       June 1987


           Errors: Cursor

           Deletes the association between the resource id and the
           cursor.  The cursor storage will be freed when no other
           resource references it.

RecolorCursor
           cursor: CURSOR
           fore-red, fore-green, fore-blue: CARD16
           back-red, back-green, back-blue: CARD16

           Errors: Cursor

           Changes the color of a cursor.  If the cursor is being
           displayed on a screen, the change is visible immediately.

QueryBestSize
           class: {Cursor, Tile, Stipple}
           drawable: DRAWABLE
           width, height: CARD16
       =>
           width, height: CARD16

           Errors: Drawable, Value, Match

           Returns the "best" size that is "closest" to the argument
           size.  For Cursor, this is the largest size that can be
           fully displayed.  For Tile, this is the size that can be
           tiled "fastest".  For Stipple, this is the size that can
           be stippled "fastest".

           For Cursor, the drawable indicates the desired screen.  For
           Tile and Stipple, the drawable indicates screen, and also
           possibly window class and depth; an InputOnly window cannot
           be used as the drawable for Tile or Stipple (else a Match
           error).

QueryExtension
           name: STRING8
       =>
           present: BOOL
           major-opcode: CARD8
           first-event: CARD8
           first-error: CARD8

           Determines if the named extension is present.  If so, the
           major opcode for the extension is returned, if it has one,
           otherwise zero is returned.  Any minor opcode and the request
           formats are specific to the extension.  If the extension
           involves additional event types, the base event type code is
           returned, otherwise zero is returned.  The format of the



M.I.T.                                                         [Page 81]

RFC 1013                                                       June 1987


           events is specific to the extension.  If the extension
           involves additional error codes, the base error code is
           returned, otherwise zero is returned.  The format of
           additional data in the errors is specific to the extension.

           The extension name should be in the ASCII encoding, and
           upper/lower case matters.

ListExtensions
       =>
           names: LISTofSTRING8

           Returns a list of all extensions supported by the server.

SetKeyboardMapping
           map: LISTofCARD8
       =>
           status: {Success, Busy}

           Errors: Value

           Sets the mapping of the keyboard.  Elements of the list are
           indexed starting from one.  The list must be of length 255.
           The index is a "core" keycode, and the element of the list
           defines the "effective" keycode.

           A zero element disables a key, no elements can have values 1
           through 7, and no two elements (with index larger than 7) can
           have the same non-zero value.  If the keyboard does not
           really generate a given keycode, specifying a non-zero value
           for that core keycode has no effect.

           Elements 6 and 7 of the map must always be zero.  The first
           five elements are special:  they specify the keycodes (if
           any) that correspond to the Mod1 through Mod5 modifiers.
           Setting one of these entries to zero disables use of that
           modifier bit.  No two of the firstfive elements can have the
           same non-zero value.

           A server can impose restrictions on how keyboards get
           remapped, e.g., if certain keys do not generate up
           transitions in hardware.

           If any of the keys or modifiers to be altered are currently
           in the down state, the status reply is Busy and the mapping
           is not changed.

GetKeyboardMapping
       =>
           map: LISTofCARD8




M.I.T.                                                         [Page 82]

RFC 1013                                                       June 1987


           Errors: Value

           Returns the current mapping of the keyboard.  Elements of the
           list are indexed starting from one.  The length of the list
           is 255.

           The nominal mapping for a keyboard is almost the identity
           mapping, except that map[i]=0 for keycodes that have no
           corresponding physical key, and the first five entries
           indicate the keycodes (if any) corresponding to the Mod1
           through Mod5 modifier bits.

ChangeKeyboardControl
           value-mask: BITMASK
           value-list: LISTofVALUE

           Errors: Match Value

           Controls various aspects of the keyboard.  The value-mask and
           value-list specify which controls are to be changed.  The
           possible values are:

               key-click-percent: INT8
               bell-percent: INT8
               bell-pitch: INT16
               bell-duration: INT16
               led: CARD8
               led-mode: {On, Off}
               key: KEYCODE
               auto-repeat-mode: {On, Off, Default}

           Key-click-percent sets the volume for key clicks between 0
           (off) and 100 (loud) inclusive, if possible.  Setting to -1
           restores the default. Other negative values generate a Value
           error.

           Bell-percent sets the base volume for the bell between 0
           (off) and 100 (loud) inclusive, if possible.  Setting to -1
           restores the default. Other negative values generate a Value
           error.

           Bell-pitch sets the pitch (specified in Hz) of the bell, if
           possible. Setting to -1 restores the default.  Other
           negative values generate a Value error.

           Bell-duration sets the duration (specified in milliseconds)
           of the bell, if possible.  Setting to -1 restores the
           default.  Other negative values generate a Value error.

           If both led-mode and led are specified, then the state of
           that LED is changed, if possible.  If only led-mode is



M.I.T.                                                         [Page 83]

RFC 1013                                                       June 1987


           specified, then the state of all LEDs are changed, if
           possible.  At most 32 LEDs are supported, numbered from one.
           It is a Match error if an led is specified without an
           led-mode.

           If both auto-repeat-mode and key are specified, then the
           auto-repeat mode of that key is changed, if possible.  If
           only auto-repeat-mode is specified, then the global
           auto-repeat mode for the entire keyboard is changed, if
           possible, without affecting the per-key settings.  It is
           a Match error if a key is specified without an
           auto-repeat-mode.

           A bell generator connected with the console but not directly
           on the keyboard is treated as if it were part of the
           keyboard.

           The order in which controls are verified and altered is
           server dependent.  If an error is generated, a subset of the
           controls may have been altered.

GetKeyboardControl
       =>
           key-click-percent: CARD8
           bell-percent: CARD8
           bell-pitch: CARD16
           bell-duration: CARD16
           led-mask: CARD32
           global-auto-repeat: {On, Off}
           auto-repeats: LISTofCARD8

           Errors: Match

           Returns the current control values for the keyboard.  For the
           LEDs, the least significant bit of led-mask corresponds to
           LED one, and each one bit in led-mask indicates an LED that
           is lit. Auto-repeats is a bit vector; each one bit indicates
           that auto-repeat is enabled for the corresponding key.  The
           vector is represented as 32 bytes.  Byte N (from 0) contains
           the bits for keys 8N to 8N+7, with the least significant bit
           in the byte representing key 8N.

Bell
           percent: INT8

           Errors: Match, Value

           Rings the bell on the keyboard at the specified volume
           relative to the base volume for the keyboard, if possible.
           Percent, which can range from -100 to 100 inclusive, is added
           to the base volume, and the sum limited to the range 0 to 100



M.I.T.                                                         [Page 84]

RFC 1013                                                       June 1987


           inclusive.

SetPointerMapping
           map: LISTofCARD8
       =>
           status: {Success, Busy}

           Errors: Value

           Sets the mapping of the pointer.  Elements of the list are
           indexed starting from one.  The length of the list must be
           the same as GetPointerMapping would return.  The index is a
           "core" button number, and the element of the list defines
           the "effective" number.

           A zero element disables a button, and elements are not
           restricted in   value by the number of physical buttons, but
           no two elements can have the same non-zero value.

           If any of the buttons to be altered are currently in the
           down state,the status reply is Busy and the mapping is not
           changed.

GetPointerMapping
       =>
           map: LISTofCARD8

           Errors: Value

           Returns the current mapping of the pointer.  Elements of the
           list are indexed starting from one.  The length of the list
           indicates the number of physical buttons.

           The nominal mapping for a pointer is the identity mapping;
           map[i]=i.

ChangePointerControl
           do-acceleration, do-threshold: BOOL
           acceleration-numerator, acceleration-denominator: INT16
           threshold: INT16

           Errors: Match, Value

           Defines how the pointer moves.  The acceleration is a
           multiplier for movement, expressed as a fraction.  For
           example, specifying 3/1 means the pointer moves three times
           as fast as normal. The fraction may be rounded arbitrarily
           by the server.  Acceleration only takes effect if the
           pointer moves more than threshold pixels at once, and only
           applies to the amount beyond the threshold.  Setting a
           value to -1 restores the default. Other negative values



M.I.T.                                                         [Page 85]

RFC 1013                                                       June 1987


           generate a Value error, as does a zero value for
           acceleration-denominator.

GetPointerControl
       =>
           acceleration-numerator, acceleration-denominator: CARD16
           threshold: CARD16

           Errors: Match

           Returns the current acceleration and threshold for the
           pointer.

SetScreenSaver
           timeout, interval: INT16
           prefer-blanking: {Yes, No, Default}
           allow-exposures: {Yes, No, Default}

           Errors: Value

           Timeout and interval are specified in minutes; setting a
           value to -1 restores the default.  Other negative values
           generate a Value error. If the timeout value is zero,
           screen-saver is disabled.  If the timeout value is
           non-zero, screen-saver is enabled.  Once screen-saver
           is enabled, if no input from the keyboard or pointer is
           generated for timeout minutes, screen-saver is activated.
           For each screen, if blanking is preferred and the hardware
           supports video blanking, the screen will simply go blank.
           Otherwise, if either exposures are allowed or the screen
           can be regenerated without sending exposure events to
           clients, the screen is tiled with the root window
           background tile, randomly re-origined each interval
           minutes if the interval value is non-zero.  Otherwise, the
           state of the screen does not change and screen-saver is not
           activated.  Screen-saver is deactivated, and all screen
           states are restored, at the next keyboard or pointer input
           or at the next ForceScreenSaver with mode Reset.

GetScreenSaver
       =>
           timeout, interval: CARD16
           prefer-blanking: {Yes, No}
           allow-exposures: {Yes, No}

           Returns the current screen-saver control values.

ForceScreenSaver
           mode: {Activate, Reset}

           If the mode is Activate and screen-saver is currently



M.I.T.                                                         [Page 86]

RFC 1013                                                       June 1987


           deactivated, then screen-saver is activated (even if
           screen-saver has been disabled with a timeout value of zero).
           If the mode is Reset and screen-saver is currently enabled,
           then screen-saver is deactivated (if it was activated), and
           then the activation timer is reset to its initial state, as
           if device input had just been received.

ChangeHosts
           mode: {Insert, Delete}
           host: HOST

           Errors: Access, Value

           Adds or removes the specified host from the access control
           list.  When the access control mechanism is enabled and a
           host attempts to establish a connection to the server, the
           host must be in this list or the server will refuse the
           connection.

           The client must reside on the same host as the server, and/or
           have been granted permission in the initial authorization at
           connection setup.

           An initial access control list can be specified, typically
           by naming a file that the server reads at startup and reset.

ListHosts
       =>
           mode: {Enabled, Disabled}
           hosts: LISTofHOST

           Returns the hosts on the access control list, and whether use
           of the list at connection setup is currently enabled or
           disabled.

           Each HOST is padded to a multiple of four bytes.

ChangeAccessControl
           mode: {Enable, Disable}

           Errors: Value, Access

           Enables or disables the use of the access control list at
           connection setups.

           The client must reside on the same host as the server, and/or
           have been granted permission in the initial authorization at
           connection setup.

ChangeCloseDownMode
           mode: {Destroy, RetainPermanent, RetainTemporary}



M.I.T.                                                         [Page 87]

RFC 1013                                                       June 1987


           Errors: Value

           Defines what will happen to the client's resources at
           connection close. A connection starts in Destroy mode.  The
           meaning of the close-down mode is described in Section 11.

KillClient
           resource: CARD32 or AllTemporary

           Errors: Value

           If a valid resource is specified, forces a close-down of the
           client that created the resource.  If the client has already
           terminated in either RetainPermanent or RetainTemporary mode,
           all of the client's resources are destroyed (see Section 11).
           If AllTemporary is specified, then the resources of all
           clients that have terminated in RetainTemporary are
           destroyed.

NoOperation
           This request has no arguments and no results, but the request
           length field can be non-zero, allowing the request to be any
           multiple of 4 bytes in length.  The bytes contained in the
           request are uninterpreted by the server.

           This request can be used in its minimum 4 byte form as
           "padding" where necessary by client libraries that find it
           convenient to force requests to begin on 64-bit boundaries.


SECTION 11.  CONNECTION CLOSE

What happens at connection close:

           All event selections made by the client are discarded.  If
           the client has the pointer actively grabbed, an
           UngrabPointer is performed.  If the client has the keyboard
           actively grabbed,  an UngrabKeyboard is performed.  All
           passive grabs by the client are eleased.  If the client has
           the server grabbed, and UngrabServer is performed.  If
           close-down mode (see ChangeCloseDownMode) is
           RetainPermanent or RetainTemporary, then all resources
           (including colormap entries)    allocated by the client are
           marked as "permanent" or "temporary", respectively (but
           this does not prevent other clients from explicitly
           destroying them).  If the mode is Destroy, then all of the
           client's resources are destroyed as described below.

What happens when a client's resources are destroyed:

           For each window in the client's save-set, if the window



M.I.T.                                                         [Page 88]

RFC 1013                                                       June 1987


           created by the client, that save-set window is reparented to
           the closest ancestor such that the save-set window is not an
           inferior of a window created by the client.  If the save-set
           window is unmaped, a MapWindow request is performed on it.
           After save-set processing, all windows created by the client
           are destroyed.  For each non-window resource created by the
           client, the appropriate Free request is performed.  All
           colors and colormap entries allocated by the client are
           freed.

What happens when the last connection to a server closes:

           A server goes through a cycle, of having no connections and
           having some connections.  At every transition to the state
           of having no connections, the server "resets" its state, as
           if it had just been started.  This starts by destroying all
           lingering resources from clients that have terminated in
           RetainPermanent or RetainTemporary mode.  It additionally
           includes deleting all but the predefined atom identifiers,
           deleting all properties on all root windows, resetting all
           device maps and attributes (key click, bell volume,
           acceleration), resetting the access control list, restoring
           the standard root tiles and cursors, restoring the default
           font path, and restoring the input focus to state
           PointerRoot.

SECTION 12.  EVENTS

      When a button is pressed with the pointer in some window W, and
      no active pointer grab is in progress, then the ancestors if W are
      searched from the root down, looking for a passive grab to
      activate.  If no matching passive grab on the button exists, then
      an active grab is started automatically for the client receiving
      the event, and the last-pointer-grab time is set to the current
      server time. The effect is essentially equivalent to a GrabButton
      with arguments:
           event-window: the event window
           event-mask: the client's selected events on the event window
           pointer-mode and keyboard-mode: Asynchronous
           owner-events: True if the client has OwnerGrabButton selected
                   on the event window, else False
           confine-to: None
           cursor: None
   The grab is terminated automatically when all buttons are released.
   UngrabPointer and ChangeActiveGrab can both be used to modify the
   active grab.

   KeyPress
     and
   KeyRelease
     and



M.I.T.                                                         [Page 89]

RFC 1013                                                       June 1987


   ButtonPress
     and
   ButtonRelease
     and
   MotionNotify
           root, event: WINDOW
           child: WINDOW or None
           same-screen: BOOL
           root-x, root-y, event-x, event-y: INT16
           detail: <see below>
           state: SETofKEYBUTMASK
           time: TIMESTAMP

           Generated when a key or button changes state, or the pointer
           moves. The "source" of the event is the window the pointer
           is in.  The window with respect to which the event is
           normally reported is found by looking up the hierarchy
           (starting with  the source window) for the first window on
           which any client has selected interest in the event,
           provided no intervening window prohibits event generation by
           including the event type in its do-not-propagate-mask.  The
           actual window used for reporting can be modified by active
           grabs and the focus window. The window the event is reported
           with respect to is called the "event" window.

           Root is the root window of the "source" window, and root-x
           and root-y are the pointer coordinates relative to root's
           origin at the time of the event.  Event is the "event"
           window.  If the event window is on the same screen as root,
           then event-x and event-y are the pointer coordinates relative
           to the event window's origin; otherwise event-x and event-y
           are zero.  If the source window is an inferior of the event
           window, then child is set to the child of the event window
           that is an ancestor of the source window.  The state
           component gives the state of the buttons and modifier keys
           just before the event.  The detailcomponent varies with
           the event type:
               KeyPress, KeyRelease:               KEYCODE
               ButtonPress, ButtonRelease:         BUTTON
               MotionNotify:                       {Normal, Hint}

           MotionNotify events are only generated when the motion
           begins and ends in the window.  The granularity of motion
           events is not guaranteed, but a client selecting for motion
           events is guaranteed to get at least one event when the
           pointer moves and comes to rest.  Selecting PointerMotion
           receives events independent of the state of the pointer
           buttons.  By selecting some subset of Button[1-5]Motion
           instead, MotionNotify events will only be received when one
           or more of the specified buttons are pressed.  By selecting
           ButtonMotion, MotionNotify events will received only when at



M.I.T.                                                         [Page 90]

RFC 1013                                                       June 1987


           least one button is pressed.  The events are always of type
           MotionNotify, independent of the selection. If
           PointerMotionHint is selected, the server is free to send
           only one MotionNotify event (with detail Hint) to the client
           for the event window, until either the key or button state
           changes, or the pointer leaves the event window, or the
           client issues a QueryPointer or GetMotionEvents request.

   EnterNotify
     and
   LeaveNotify
           root, event: WINDOW
           child: WINDOW or None
           same-screen: BOOL
           root-x, root-y, event-x, event-y: INT16
           mode: {Normal, Grab, Ungrab}
           detail: {Ancestor, Virtual, Inferior, Nonlinear,
                    NonlinearVirtual}
           focus: BOOL
           state: SETofKEYBUTMASK
           time: TIMESTAMP

           If pointer motion causes the pointer to be in a different
           window than before, EnterNotify and LeaveNotify events are
           generated instead of a  MotionNotify event.  Only clients
           selecting EnterWindow on a window receive EnterNotify events,
           and only clients selection LeaveNotifyreceive LeaveNotify
           events.  The pointer position reported in the event is always
           the "final" position, not the "initial" position of the
           pointer.  In a LeaveNotify event, if a child of the event
           window contains the "initial" position of the pointer, then
           the child component is set to that child, otherwise it is
           None.  For an EnterNotify event, if a child of the event
           window contains the "final" pointer position, then the child
           component is set to that child, otherwise it is None.  If
           the the event window is the focus window or an inferior of
           the focus window, then focus is True, and otherwisefocus is
           False.

           Normal pointer motion events have mode Normal; pseudo-motion
           events when a grab actives have mode Grab, and pseudo-motion
           events when a grab deactivates have mode Ungrab.

       Normal events are generated as follows:

       When the pointer moves from window A to window B, and A is an
       inferior of B:
           LeaveNotify with detail Ancestor is generated on A
           LeaveNotify with detail Virtual is generated on each window
           between A and B exclusive (in that order)
           EnterNotify with detail Inferior is generated on B



M.I.T.                                                         [Page 91]

RFC 1013                                                       June 1987


       When the pointer moves from window A to window B, and B is an
       inferior of A:
           LeaveNotify with detail Inferior is generated on A
           EnterNotify with detail Virtual is generated on each window
                   between A and B exclusive (in that order)
           EnterNotify with detail Ancestor is generated on B

       When the pointer moves from window A to window B, with window C
       being their least common ancestor:
           LeaveNotify with detail Nonlinear is generated on A
           LeaveNotify with detail NonlinearVirtual is generated on each
                   window between A and C exclusive (in that order)
           EnterNotify with detail NonlinearVirtual is generated on each
                   window between C and B exclusive (in that order)
           EnterNotify with detail Nonlinear is generated on B

       When the pointer moves from window A to window B, on different
       screens:
           LeaveNotify with detail Nonlinear is generated on A
           LeaveNotify with detail NonlinearVirtual is generated on each
                   window above A up to and including its root (in
                   order)
           EnterNotify with detail NonlinearVirtual is generated on each
           window
                   from B's root down to but not including B (in order)
           EnterNotify with detail Nonlinear is generated on B

       When a pointer grab activates (but after any initial warp into a
       confine-to window), with G the grab-window for the grab and P the
       window the pointer is in:
           EnterNotify and LeaveNotify events with mode Grab are
           generated (as for Normal above) as if the pointer were to
           suddenly warp from its current position in P to some position
           in G.However,  the pointer does not warp, and the pointer
           position is used as  both the "initial"and "final" positions
           for the events.

       When a pointer grab deactivates, with G the grab-window for the
       grab and P the window the pointer is in:

           EnterNotify and LeaveNotify events with mode Ungrab are
           generated (as for Normal above) as if the pointer were to
           suddenly warp from from some position in G to its current
           position in P.  However, the pointer does not warp, and the
           current pointer position is used as both the "initial" and
           "final" positions for the events.

   FocusIn
     and
   FocusOut
           event: WINDOW



M.I.T.                                                         [Page 92]

RFC 1013                                                       June 1987


           mode: {Normal, WhileGrabbed, Grab, Ungrab}
           detail: {Ancestor, Virtual, Inferior, Nonlinear,
                    NonlinearVirtual, Pointer, PointerRoot, None}

           Generated when the input focus changes.  Reported to clients
           selecting FocusChange on the window.  Events generated by
           SetInputFocus when the keyboard is not grabbed have mode
           Normal; events generated by SetInputFocus when the keyboard
           is grabbed have mode WhileGrabbed; events generated when a
           keyboard grab actives have mode Grab, and events generated
           when a keyboard grab deactivates have mode Ungrab.

       Normal and WhileGrabbed events are generated as follows:

       When the focus moves from window A to window B, and A is an
       inferior of B, with the pointer in window P:
           FocusOut with detail Ancestor is generated on A
           FocusOut with detail Virtual is generated on each window
           between A and B exclusive (in that order)
           FocusIn with detail Inferior is generated on B
           If P is an inferior of B, but P is not A or an inferior of A
                   or an ancestor of A, FocusIn with detail Pointer is
                   generated on each window below B down to and
                   including P (in order)

       When the focus moves from window A to window B, and B is an
       inferior of A, with the pointer in window P:
           If P is an inferior of A, but P is not A or an inferior of B
                   or an ancestor of B, FocusOut with detail Pointer is
                   generated on each window from P up to but not
                   including A (in order)
           FocusOut with detail Inferior is generated on A
           FocusIn with detail Virtual is generated on each window
                   between A and B exclusive (in that order)
           FocusIn with detail Ancestor is generated on B

       When the focus moves from window A to window B, with window C
       being their least common ancestor, and with the pointer in
       window P:
           If P is an inferior of A, FocusOut with detail Pointer is
                   generated on each window from P up to but not
                   including A (in order)
           FocusOut with detail Nonlinear is generated on A
           FocusOut with detail NonlinearVirtual is generated on each
                   window between A and C exclusive (in that order)
           FocusIn with detail NonlinearVirtual is generated on each
                   window between C and B exclusive (in that order)
           FocusIn with detail Nonlinear is generated on B
           If P is an inferior of B, FocusIn with detail Pointer is
                   generated on each window below B down to and
                   including P (in order)



M.I.T.                                                         [Page 93]

RFC 1013                                                       June 1987


       When the focus moves from window A to window B, on different
       screens, with the pointer in window P:
           If P is an inferior of A, FocusOut with detail Pointer is
                   generated on each window from P up to but not
                   including A (in order)
           FocusOut with detail Nonlinear is generated on A
           FocusOut with detail NonlinearVirtual is generated on each
                   window above A up to and including its root (in
                   order)
           FocusIn with detail NonlinearVirtual is generated on each
                   window from B's root down to but not including B
                   (in order)
           FocusIn with detail Nonlinear is generated on B
           If P is an inferior of B, FocusIn with detail Pointer is
                   generated on each window below B down to and
                   including P (in order)

       When the focus moves from window A to PointerRoot (or None)
           If P is an inferior of A, FocusOut with detail Pointer is
                   generated on each window from P up to but not
                   including A (in order)
           FocusOut with detail Nonlinear is generated on A
           FocusOut with detail NonlinearVirtual is generated on each
                   window above A up to and including its root (in
                   order)
           FocusIn with detail PointerRoot (or None) is generated on
                   all root windows

       When the focus moves from PointerRoot (or None) to window A:
           FocusOut with detail PointerRoot (or None) is generated on
                   all root windows
           FocusIn with detail NonlinearVirtual is generated on each
                   window from A's root down to but not including A
                   (in order)
           FocusIn with detail Nonlinear is generated on A
           If P is an inferior of A, FocusIn with detail Pointer is
                   generated on each window below A down to and
                   including P (in order)

       When the focus moves from PointerRoot to None (or vice versa):
           FocusOut with detail PointerRoot (or None) is generated on
                   all root windows
           FocusIn with detail None (or PointerRoot) is generated on
                   all root windows

       When a keyboard grab activates, with G the grab-window for the
       grab and F the current focus:
           FocusIn and FocusOut events with mode Grab are generated (as
           for Normal above) as if the focus were to change from F to G





M.I.T.                                                         [Page 94]

RFC 1013                                                       June 1987


       When a keyboard grab deactivates, with G the grab-window for the
       grab and F the current focus:
           FocusIn and FocusOut events with mode Ungrab are generated
           (as for Normal above) as if the focus were to change from G
           to F

   KeymapNotify
           keys: LISTofCARD8

           The value is a bit vector, as described in QueryKeymap.
           Reported to clients selecting KeymapState on a window.
           Generated immediately after every EnterNotify and FocusIn.

   Expose
           window: WINDOW
           x, y, width, height: CARD16
           last-in-series: BOOL

           Reported to clients selecting Exposure on the window.
           Possibly generated when a region of the window becomes
           viewable, but might only be generated when a region becomes
           visible. All of the regions exposed by a given "action" are
           guaranteed to be reported contiguously; if last-in-series is
           False then another exposure follows.

           The x and y coordinates are relative to drawable's origin,
           and  specify the upper left corner of a rectangule.  The
           width and height specify the extent of the rectangle.

           Expose events are never generated on InputOnly windows.

GraphicsExposure
           drawable: DRAWABLE
           x, y, width, height: CARD16
           last-in-series: BOOL
           major-opcode: CARD8
           minor-opcode: CARD16

           Reported to clients selecting graphics-exposures in a
           graphics context. Generated when a destination region could
           not be computed due to an obscured or out-of-bounds source
           region.  All of the regions exposed by a given graphics
           request are guaranteed to be reported contiguously; if
           last-in-series is False then another exposure follows.

           The x and y coordinates are relative to drawable's origin,
           and specify the upper left corner of a rectangule.  The width
           and height specify the extent of the rectangle.

           The major and minor opcodes identify the graphics request
           used.  For the core protocol, major-opcode is always



M.I.T.                                                         [Page 95]

RFC 1013                                                       June 1987


           CopyArea or CopyPlane and minor-opcode is always zero.

NoExposure
           drawable: DRAWABLE
           major-opcode: CARD8
           minor-opcode: CARD16

           Reported to clients selecting graphics-exposures in a
           graphics context. Generated when a graphics request that
           might produce GraphicsExposure events does not produce any.
           The drawable specifies the destination used for the
           graphics request.

           The major and minor opcodes identify the graphics request
           used.  For the core protocol, major-opcode is always CopyArea
           or CopyPlane and minor-opcode is always zero.

VisibilityNotify
           window: WINDOW
           state: {Unobscured, PartiallyObscured, FullyObscured}

           Reported to clients selecting VisibilityChange on the
           window.  In the following, the state of the window is
           calculated ignoring all of the window's subwindows.  When
           a window changes state from partially or fully obscured or
           not viewable to viewable and completely unobscured, an
           event with Unobscured  is generated.  When a window changes
           state from a) viewable and completely unobscured or b) not
           viewable, to viewable and partially obscured, an event with
           PartiallyObscured is generated.  When a window changes state
           from a) viewable and completely unobscured or b) viewable and
           partially obscured or c) not viewable, to viewable and fully
           obscured, an event with FullyObscured is generated.

           VisibilityNotify events are never generated on InputOnly
           windows.

CreateNotify
           parent, window: WINDOW
           x, y: INT16
           width, height, border-width: CARD16
           override-redirect: BOOL

           Reported to clients selecting SubstructureNotify on the
           parent. Generated when the window is created.  The arguments
           are as in the CreateWindow request.








M.I.T.                                                         [Page 96]

RFC 1013                                                       June 1987


DestroyNotify
           event, window: WINDOW

           Reported to clients selecting StructureNotify on the window,
           and to clients selecting SubstructureNotify on the parent.
           Generated when the window is destroyed.  "Event" is the
           window on which the event was   generated, and "window" is
           the window that is destroyed.

UnmapNotify
           event, window: WINDOW
           from-configure: BOOL

           Reported to clients selecting StructureNotify on the window,
           and to clients selecting SubstructureNotify on the parent.
           Generated when the window changes state from mapped to
           unmapped. "Event" is the window on which the event was
           generated, and "window" is the window that is unmapped.  The
           from-configure flag is True if the event was generated  as a
           result of the window's parent being resized when the window
           itself had a win-gravity of Unmap.

MapNotify
           event, window: WINDOW
           override-redirect: BOOL

           Reported to clients selecting StructureNotify on the window,
           and to clients selecting SubstructureNotify on the parent.
           Generated when the window changes state from unmapped to
           mapped. "Event" is the window on which the event was
           generated, and "window" is the window that is mapped.  The
           override-redirect flag is from the window's attribute.

MapRequest
           parent, window: WINDOW

           Reported to the client selecting SubstructureRedirect on the
           parent. Generated when a MapWindow request is issued on an
           unmapped window with an override-redirect attribute of False.

ReparentNotify
           event, window, parent: WINDOW
           x, y: INT16
           override-redirect: BOOL

           Reported to clients selecting SubstructureNotify on either
           the old or the new parent, and to clients selecting
           StructureNotify on the window.  Generated when the window
           is reparented.  "Event" is the window on which the event
           was generated, "window" is the window that has been
           re-rooted, and "parent" specifies the new parent.  The x



M.I.T.                                                         [Page 97]

RFC 1013                                                       June 1987


           and y coordinates are relative to the new parent's origin,
           and specify the position of the upper left outer corner of
           the window.  The override-redirect flag is from the
           window's attribute.

ConfigureNotify
           event, window: WINDOW
           x, y: INT16
           width, height, border-width: CARD16
           above-sibling: WINDOW or None
           override-redirect: BOOL

           Reported to clients selecting StructureNotify on the window,
           and to clients selecting SubstructureNotify on the parent.
           Generated when a ConfigureWindow request actually changes the
           state of the window. "Event" is the window on which the event
           was generated, and "window" is the window that is changed.
           If above-sibling is None, then the window is on the bottom of
           the stack with respect to siblings; otherwise, the window is
           immediately on top of the specified sibling.  The
           override-redirect flag is from the window's attribute.

GravityNotify
           event, window: WINDOW
           x, y: INT16

           Reported to clients selecting SubstructureNotify on the
           parent, and to clients selecting StructureNotify on the
           window.  Generated when a window is moved because of a
           change in size of the parent.  "Event" is the window on
           which the event was generated, and "window" is the
           window that is moved.

ResizeRequest
           window: WINDOW
           width, height: CARD16

           Reported to the client selecting ResizeRedirect on the
           window. Generated when a ConfigureWindow request by some
           other client on the window attempts to change the size of the
           window. The width and height are the inside size, not
           including the border.

ConfigureRequest
           parent, window: WINDOW
           x, y: INT16
           width, height, border-width: CARD16
           above-sibling: WINDOW or None

           Reported to the client selecting SubstructureRedirect on the
           parent. Generated when a ConfigureWindow request is issued on



M.I.T.                                                         [Page 98]

RFC 1013                                                       June 1987


           the window by some other client.  The geometry is as derived
           from the request.  The above-sibling is the sibling the
           window should be placed directly on top of; if None, then the
           window should be placed on the bottom.

CirculateNotify
           event, window: WINDOW
           place: {Top, Bottom}

           Reported to clients selecting StructureNotify on the window,
           and to clients selecting SubstructureNotify on the parent.
           Generated when the window is actually restacked from a
           CirculateWindow request.  "Event" is the window on which the
           event was generated, and "window" is the window that is
           restacked.  If place is Top, the window is now on top of all
           siblings; otherwise it is below all siblings.

CirculateRequest
           parent, window: WINDOW
           place: {Top, Bottom}

           Reported to the client selecting SubstructureRedirect on the
           parent. Generated when a CirculateWindow request is issued on
           the parent and a window actually needs to be restacked.  The
           window specifies the window to be restacked, and place
           specifies what the new position in the stacking order should
           be.

PropertyNotify
           window: WINDOW
           atom: ATOM
           state: {NewValue, Deleted}
           time: TIMESTAMP

           Reported to clients selecting PropertyChange on the window.
           Generated when a property of the window is changed.  The
           timestamp indicates the server time when the property was
           changed.

SelectionClear
           owner: WINDOW
           selection: ATOM
           time: TIMESTAMP

           Reported to the current owner of a selection.  Generated on
           the window losing ownership when a new owner is being
           defined.  The timestamp is the last-change time recorded for
           the selection.

SelectionRequest
           owner: WINDOW



M.I.T.                                                         [Page 99]

RFC 1013                                                       June 1987


           selection: ATOM
           target: ATOM
           property: ATOM or None
           requestor: WINDOW
           time: TIMESTAMP or CurrentTime

           Reported to the owner of a selection.  Generated when a
           client issues a ConvertSelection request. The arguments are
           as in the request.

           The owner should convert the selection based on the specified
           target type.  If a property is specified, the owner should
           store the result as that property on the requestor window,
           and then send a SelectionNotify event to the requestor using
           SendEvent.  If the selection cannot be converted as
           requested, the owner should send a SelectionNotify with the
           property set to None.

SelectionNotify
           requestor: WINDOW
           selection, target: ATOM
           property: ATOM or None
           time: TIMESTAMP or CurrentTime

           This event is only generated by clients using SendEvent.  The
           owner of a selection should send this event to a requestor
           when a selection has been converted and stored as a property,
           or when a selection conversion could not be performed
           (indicated with property None).

ColormapNotify
           window: WINDOW
           colormap: COLORMAP or None
           new: BOOL
           state: {Installed, Uninstalled}

           Reported to clients selecting ColormapChange on the window.
           Generated with value True for new when the colormap attribute
           of the window is changed.  Generated with value False for new
           when the colormap of a window is installed or uninstalled. In
           either case, state indicates whether the colormap is
           currently installed.

ClientMessage
           window: WINDOW
           type: ATOM
           format: {8, 16, 32}
           data: LISTofINT8 or LISTofINT16 or LISTofINT32

           This event is only generated by clients using SendEvent.  The
           type specifies how the data is to be interpreted by the



M.I.T.                                                        [Page 100]

RFC 1013                                                       June 1987


           receiving client; the server places no interpretation on the
           type or the data.  The format specifies whether the data
           should be viewed as a list of 8-bit, 16-bit, or 32-bit
           quantities, so that the server can correctly byte-swap as
           necessary. The data always consists of either 20 8-bit values
           or 10 16-bit values or 5 32-bit values, although particular
           message types might not make use of all of these values.

SECTION 13.  FLOW CONTROL AND CONCURRENCY

    Whenever the server is writing to a given connection, it is
    permissible for the server to stop reading from that connection (but
    if the writing would block it must continue to service other
    connections).  The server is not required to buffer more than a
    single request per connection at one time.  For a given connection
    to the server, a client can block while reading from the connection,
    but should undertake to read (events and errors) when writing would
    block. Failure on the part of a client to obey this rule could
    result in a deadlocked connection, although deadlock is probably
    unlikely unless the transport layer has very little buffering, or
    unless the client attempts to send large numbers of requests without
    ever reading replies or checking for errors and events.

    If a server is implemented with internal concurrency, the overall
    effect must be as if individual requests are executed to completion
    in some serial order, and that requests from a given connection are
    executed in delivery order (i.e., the total execution order is a
    shuffle of the individual streams).  The "execution" of a request
    includes validating all arguments, collecting all data for any
    reply, and generating (and queueing) all required events, but does
    not include the actual transmission of the reply and the events.
    In addition, the   effect of any other "cause" (e.g., activation of
    a grab, pointer motion) that can generate multiple events must
    effectively generate (and queue) all required events indivisibly
    with respect to all other causes and requests.



















M.I.T.                                                        [Page 101]


Html markup produced by rfcmarkup 1.108, available from http://tools.ietf.org/tools/rfcmarkup/