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]