     [file version.txi not included]

XlibScm
*******

This manual documents the X Interface for SCM Language (version SCMVERSION, SCMDATE).

Copyright © 1999 Free Software Foundation, Inc.

     Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies.

     Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one.

     Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that this permission notice may be stated in a translation approved by the author.

XlibScm
*******

XlibScm is a SCM interface to X. The X Window System is a network-transparent window system that was designed at MIT. SCM is a portable Scheme implementation written in C. The interface can be compiled into SCM or, on those platforms supporting dynamic linking, compiled separately and loaded with (require 'Xlib).

Much of this X documentation is dervied from:

Xlib - C Language X Interface
X Consortium Standard
X Version 11, Release 6.3

The X Window System is a trademark of X Consortium, Inc.

TekHVC is a trademark of Tektronix, Inc.

Copyright (C) 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1994, 1996 X Consortium

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE X CONSORTIUM BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Except as contained in this notice, the name of the X Consortium shall not be used in advertising or otherwise to promote the sale, use or other dealings in this Software without prior written authorization from the X Consortium.

Copyright (C) 1985, 1986, 1987, 1988, 1989, 1990, 1991 by Digital Equipment Corporation

Portions Copyright (C) 1990, 1991 by Tektronix, Inc.

Permission to use, copy, modify and distribute this documentation for any purpose and without fee is hereby granted, provided that the above copyright notice appears in all copies and that both that copyright notice and this permission notice appear in all copies, and that the names of Digital and Tektronix not be used in in advertising or publicity pertaining to this documentation without specific, written prior permission.  Digital and Tektronix makes no representations about the suitability of this documentation for any purpose.  It is provided ``as is'' without express or implied warranty.

Display and Screens
*******************

 -- Function: x:open-display display-name
     DISPLAY-NAME Specifies the hardware display name, which determines the display and communications domain to be used.  On a POSIX-conformant system, if the display-name is #f, it defaults to the value of the DISPLAY environment variable.

     The encoding and interpretation of DISPLAY-NAME is implementation-dependent.  On POSIX-conformant systems, the DISPLAY-NAME or DISPLAY environment variable can be a string in the format:

      -- Special Form: hostname:number.screen-number

          HOSTNAME specifies the name of the host machine on which the display is physically attached.  Follow the HOSTNAME with either a single colon (:) or a double colon (::).

          NUMBER specifies the number of the display server on that host machine.  You may optionally follow this display number with a period (.).  A single CPU can have more than one display.  Multiple displays are usually numbered starting with zero.

          SCREEN-NUMBER specifies the screen to be used on that server. Multiple screens can be controlled by a single X server.  The SCREEN-NUMBER sets an internal variable that can be accessed by using the x:default-screen procedure.

 -- Function: x:close display
     DISPLAY specifies the connection to the X server.

     The x:close function closes the connection to the X server for the DISPLAY specified and destroys all windows, resource IDs (Window, Font, Pixmap, Colormap, Cursor, and GContext), or other resources that the client has created on this display, unless the close-down mode of the resource has been changed (see x:set-close-down-mode).  Therefore, these windows, resource IDs, and other resources should not be used again or an error will be generated.  Before exiting, you should call X:CLOSE-DISPLAY or X:FLUSH explicitly so that any pending errors are reported.

 -- Function: x:protocol-version display
     Returns cons of the major version number (11) of the X protocol associated with the connected DISPLAY and the minor protocol revision number of the X server.

 -- Function: x:server-vendor display
     Returns a string that provides some identification of the owner of the X server implementation.  The contents of the string are implementation-dependent.

 -- Function: x:vendor-release display
     Returns a number related to a vendor's release of the X server.

A display consists of one or more Screens.  Each screen has a root-window, default-graphics-context, and colormap.

 -- Function: x:screen-count display
     Returns the number of available screens.

 -- Function: x:default-screen display
     Returns the default screen number specified by the x:open-display function.  Use this screen number in applications which will use only a single screen.

 -- Function: x:root-window display screen-number
 -- Function: x:root-window display
     SCREEN-NUMBER, if givien, specifies the appropriate screen number on the host server.  Otherwise the default-screen for DISPLAY is used.

     Returns the root window for the specified SCREEN-NUMBER.  Use x:root-window for functions that need a drawable of a particular screen or for creating top-level windows.

 -- Function: x:root-window window
     Returns the root window for the specified WINDOW's screen.

 -- Function: x:default-colormap display screen-number
 -- Function: x:default-colormap display
 -- Function: x:default-colormap window
     Returns the default colormap of the specified screen.

 -- Function: x:default-ccc display screen-number
 -- Function: x:default-ccc display
 -- Function: x:default-ccc window
     Returns the default Color-Conversion-Context (ccc) of the specified screen.

 -- Function: x:default-gc display screen-number
 -- Function: x:default-gc display
 -- Function: x:default-gc window
     Returns the default graphics-context of the specified screen.

 -- Function: x:screen-depths display screen-number
 -- Function: x:screen-depths display
 -- Function: x:screen-depths window
     Returns an array of depths supported by the specified screen.

The Visual type describes possible colormap depths and arrangements.

 -- Function: x:default-visual display screen-number
 -- Function: x:default-visual display
 -- Function: x:default-visual window
     Returns the default Visual type for the specified screen.

 -- Function: x:make-visual display depth class
 -- Function: x:make-visual window depth class

     The integer DEPTH specifies the number of bits per pixel. The CLASS argument specifies one of the possible visual classes for a screen:

       * x:Static-Gray

       * x:Static-Color

       * x:True-Color

       * x:Gray-Scale

       * x:Pseudo-Color

       * x:Direct-Color

     X:make-visual returns a visual type for the screen specified by DISPLAY or WINDOW if successful; #f if not.

 -- Function: x:visual-class visual
 -- Function: x:visual-class screen
 -- Function: x:visual-class display
     Returns the (integer) visual class of its argument.

 -- Function: x:visual-geometry visual
 -- Function: x:visual-geometry screen
 -- Function: x:visual-geometry display
     Returns a list of the:

       * red_mask

       * green_mask

       * blue_mask

       * colormap_size

 -- Function: x:screen-cells display screen-number
 -- Function: x:screen-cells display
 -- Function: x:screen-cells window
     Returns the number of entries in the default colormap.

 -- Function: x:screen-depth display screen-number
     Returns the depth of the root window of the specified screen.
 -- Function: x:screen-depth display
 -- Function: x:screen-depth window
 -- Function: x:screen-depth visual
     Returns the depth of argument.

     The depth of a window or pixmap is the number of bits per pixel it has. The depth of a graphics context is the depth of the drawables it can be used in conjunction with graphics output.

 -- Function: x:screen-size display screen-number
 -- Function: x:screen-size display
 -- Function: x:screen-size window
     Returns a list of integer height and width of the screen in pixels.

 -- Function: x:screen-dimensions display screen-number
 -- Function: x:screen-dimensions display
 -- Function: x:screen-dimensions window
     Returns a list of integer height and width of the screen in millimeters.

 -- Function: x:screen-white display screen-number
 -- Function: x:screen-white display
 -- Function: x:screen-white window
     Returns the white pixel value of the specified screen.

 -- Function: x:screen-black display screen-number
 -- Function: x:screen-black display
 -- Function: x:screen-black window
     Returns the black pixel value of the specified screen.

Drawables
*********

A Drawable is either a window or pixmap.

Windows and Pixmaps
===================

 -- Function: x:create-window window position size border-width depth class visual field-name value ...
     Creates and returns an unmapped Input-Output subwindow for a specified parent WINDOW and causes the X server to generate a CreateNotify event.  The created window is placed on top in the stacking order with respect to siblings.  Any part of the window that extends outside its parent WINDOW is clipped.  The BORDER-WIDTH for an x:Input-Only window must be zero.

     The coordinate system has the X axis horizontal and the Y axis vertical with the origin [0, 0] at the upper-left corner.  Coordinates are integral, in terms of pixels, and coincide with pixel centers.  Each window and pixmap has its own coordinate system.  For a window, the origin is inside the border at the inside, upper-left corner.

     CLASS can be x:Input-Output, x:Input-Only, or x:Copy-From-Parent. For class x:Input-Output, the VISUAL type and DEPTH must be a combination supported for the screen.  The DEPTH need not be the same as the parent, but the parent must not be a window of class x:Input-Only.  For an x:Input-Only window, the DEPTH must be zero, and the VISUAL must be one supported by the screen.

     The returned window will have the attributes specified by FIELD-NAMEs and VALUE.

 -- Function: x:create-window window position size border-width border background
     The returned window inherits its depth, class, and visual from its parent.  All other window attributes, except BACKGROUND and BORDER, have their default values.

 -- Function: x:create-pixmap drawable size depth
 -- Function: x:create-pixmap display size depth

     SIZE is a list, vector, or pair of nonzero integers specifying the width and height desired in the new pixmap.

     X:CREATE-PIXMAP returns a new pixmap of the width, height, and DEPTH specified.  It is valid to pass an x:Input-Only window to the drawable argument.  The DEPTH argument must be one of the depths supported by the screen of the specified DRAWABLE.

 -- Function: x:close window
     Destroys the specified WINDOW as well as all of its subwindows and causes the X server to generate a DestroyNotify event for each window. The window should not be used again.  If the window specified by the WINDOW argument is mapped, it is unmapped automatically.  The ordering of the DestroyNotify events is such that for any given window being destroyed, DestroyNotify is generated on any inferiors of the window before being generated on the window itself.  The ordering among siblings and across subhierarchies is not otherwise constrained.  If the WINDOW you specified is a root window, an error is signaled. Destroying a mapped WINDOW will generate x:Expose events on other windows that were obscured by the window being destroyed.

 -- Function: x:close pixmap
     Deletes the association between the PIXMAP and its storage.  The X server frees the pixmap storage when there are no references to it.

 -- Function: x:window-geometry drawable
     Returns a list of:

     coordinates
          list of x and y coordinates that define the location of the DRAWABLE.  For a window, these coordinates specify the upper-left outer corner relative to its parent's origin.  For pixmaps, these coordinates are always zero.

     size
          list of the DRAWABLE's dimensions (width and height).  For a window, these dimensions specify the inside size, not including the border.

     border-width
          The border width in pixels.  If the DRAWABLE is a pixmap, this is zero.

     depth
          The depth of the DRAWABLE (bits per pixel for the object).

 -- Function: x:window-geometry-set! window field-name value ...
     Changes the Configuration components specified by FIELD-NAMEs for the specified WINDOW.

These are the attributes settable by x:window-geometry-set!. That these attributes are encoded by small integers -- just like those of the next section.  Be warned therefore that confusion of attribute names will likely not signal errors, just cause mysterious behavior.

 -- Attribute: x:CWX
 -- Attribute: x:CWY
 -- Attribute: x:CW-Width
 -- Attribute: x:CW-Height
     The x:CWX and x:CYY members are used to set the window's x and y coordinates, which are relative to the parent's origin and indicate the position of the upper-left outer corner of the window.  The x:CW-Width and x:CW-Height members are used to set the inside size of the window, not including the border, and must be nonzero.  Attempts to configure a root window have no effect.

     If a window's size actually changes, the window's subwindows move according to their window gravity.  Depending on the window's bit gravity, the contents of the window also may be moved

 -- Attribute: x:CW-Border-Width
     The integer x:CW-Border-Width is used to set the width of the border in pixels.  Note that setting just the border width leaves the outer-left corner of the window in a fixed position but moves the absolute position of the window's origin.  It is an error to set the border-width attribute of an InputOnly window nonzero.

 -- Attribute: x:CW-Sibling
     The sibling member is used to set the sibling window for stacking operations.

 -- Attribute: x:CW-Stack-Mode
     The x:CW-Stack-Mode member is used to set how the window is to be restacked and can be set to x:Above, x:Below, x:Top-If, x:Bottom-If, or x:Opposite.

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

x:Above
     The window is placed just above the sibling.

x:Below
     The window is placed just below the sibling.

x:Top-If
     If the sibling occludes the window, the window is placed at the top of the stack.

x:Bottom-If
     If the window occludes the sibling, the window is placed at the bottom of the stack.

x:Opposite
     If the sibling occludes the window, the window is placed at the top of the stack.  If the window occludes the sibling, the 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:

x:Above
     The window is placed at the top of the stack.

x:Below
     The window is placed at the bottom of the stack.

x:Top-If
     If any sibling occludes the window, the window is placed at the top of the stack.

x:Bottom-If
     If the window occludes any sibling, the window is placed at the bottom of the stack.

x:Opposite
     If any sibling occludes the window, the window is placed at the top of the stack.  If the window occludes any sibling, the window is placed at the bottom of the stack.

Window Attributes
=================

 -- Function: x:window-set! window field-name value ...
     Changes the components specified by FIELD-NAMEs for the specified WINDOW.  The restrictions are the same as for x:create-window.  The order in which components are verified and altered is server dependent.  If an error occurs, a subset of the components may have been altered.

The x:create-window and x:window-set! procedures take five and one argument (respectively) followed by pairs of arguments, where the first is one of the property-name symbols (or its top-level value) listed below; and the second is the value to associate with that property.

 -- Attribute: x:CW-Back-Pixmap
     Sets the background pixmap of the WINDOW to the specified pixmap. The background pixmap can immediately be freed if no further explicit references to it are to be made.  If x:Parent-Relative is specified, the background pixmap of the window's parent is used, or on the root window, the default background is restored.  It is an error to perform this operation on an x:Input-Only window.  If the background is set to #f or None, the window has no defined background.

 -- Attribute: x:CW-Back-Pixel
     Sets the background of the WINDOW to the specified pixel value. Changing the background does not cause the WINDOW contents to be changed.  It is an error to perform this operation on an x:Input-Only window.

 -- Attribute: x:CW-Border-Pixmap
     Sets the border pixmap of the WINDOW to the pixmap you specify. The border pixmap can be freed if no further explicit references to it are to be made.  If you specify x:Copy-From-Parent, a copy of the parent window's border pixmap is used.  It is an error to perform this operation on an x:Input-Only WINDOW.

 -- Attribute: x:CW-Border-Pixel
     Sets the border of the WINDOW to the pixel VALUE.  It is an error to perform this operation on an x:Input-Only window.

 -- Attribute: x:CW-Bit-Gravity
 -- Attribute: x:CW-Win-Gravity
     The bit gravity of a window defines which region of the window should be retained when an x:Input-Output window is resized.  The default value for the bit-gravity attribute is x:Forget-Gravity.  The window gravity of a window allows you to define how the x:Input-Output or x:Input-Only window should be repositioned if its parent is resized.  The default value for the win-gravity attribute is x:North-West-Gravity.

     If the inside width or height of a window is not changed and if the window is moved or its border is changed, then the contents of the window are not lost but move with the window.  Changing the inside width or height of the window causes its contents to be moved or lost (depending on the bit-gravity of the window) and causes children to be reconfigured (depending on their win-gravity).  For a change of width and height, the (x, y) pairs are defined:

     Gravity Direction
     Coordinates
     x:North-West-Gravity
     (0, 0)
     x:North-Gravity
     (Width/2, 0)
     x:North-East-Gravity
     (Width, 0)
     x:West-Gravity
     (0, Height/2)
     x:Center-Gravity
     (Width/2, Height/2)
     x:East-Gravity
     (Width, Height/2)
     x:South-West-Gravity
     (0, Height)
     x:South-Gravity
     (Width/2, Height)
     x:South-East-Gravity
     (Width, Height)

     When a window with one of these bit-gravity values 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 x:Gravity-Notify event is generated (see section 10.10.5).

     A bit-gravity of x:Static-Gravity 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 (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 x:Static-Gravity still only takes effect when the width or height of the window is changed, not when the window is moved.

     A bit-gravity of x:Forget-Gravity indicates that the window's contents are always discarded after a size change, even if a backing store or save under has been requested.  The window is tiled with its background and zero or more x:Expose events are generated.  If no background is defined, the existing screen contents are not altered.  Some X servers may also ignore the specified bit-gravity and always generate x:Expose events.

     The contents and borders of inferiors are not affected by their parent's bit-gravity.  A server is permitted to ignore the specified bit-gravity and use x:Forget-Gravity instead.

     A win-gravity of x:Unmap-Gravity is like x:North-West-Gravity (the window is not moved), except the child is also unmapped when the parent is resized, and an x:Unmap-Notify event is generated.

 -- Attribute: x:CW-Backing-Store
     Some implementations of the X server may choose to maintain the contents of x:Input-Output windows.  If the X server maintains the contents of a window, the off-screen saved pixels are known as backing store.  The backing store advises the X server on what to do with the contents of a window.  The backing-store attribute can be set to x:Not-Useful (default), x:When-Mapped, or x:Always.  A backing-store attribute of x:Not-Useful advises the X server that maintaining contents is unnecessary, although some X implementations may still choose to maintain contents and, therefore, not generate x:Expose events.  A backing-store attribute of x:When-Mapped advises the X server that maintaining contents of obscured regions when the window is mapped would be beneficial.  In this case, the server may generate an x:Expose event when the window is created.  A backing-store attribute of x:Always advises the X server that maintaining contents even when the window is unmapped would be beneficial.  Even if the window is larger than its parent, this is a request to the X server to maintain complete contents, not just the region within the parent window boundaries.  While the X server maintains the window's contents, x:Expose events normally are not generated, but the X server may stop maintaining contents at any time.

     When the contents of obscured regions of a window are being maintained, regions obscured by noninferior windows are included in the destination of graphics requests (and source, when the window is the source). However, regions obscured by inferior windows are not included.

 -- Attribute: x:CW-Backing-Planes
 -- Attribute: x:CW-Backing-Pixel
     You can set backing planes to indicate (with bits set to 1) which bit planes of an x:Input-Output window hold dynamic data that must be preserved in backing store and during save unders.  The default value for the backing-planes attribute is all bits set to 1.  You can set backing pixel to specify what bits to use in planes not covered by backing planes.  The default value for the backing-pixel attribute is all bits set to 0.  The X server is free to save only the specified bit planes in the backing store or the save under and is free to regenerate the remaining planes with the specified pixel value.  Any extraneous bits in these values (that is, those bits beyond the specified depth of the window) may be simply ignored.  If you request backing store or save unders, you should use these members to minimize the amount of off-screen memory required to store your window.

 -- Attribute: x:CW-Override-Redirect
     To control window placement or to add decoration, a window manager often needs to intercept (redirect) any map or configure request.  Pop-up windows, however, often need to be mapped without a window manager getting in the way.  To control whether an x:Input-Output or x:Input-Only window is to ignore these structure control facilities, use the override-redirect flag.

     The override-redirect flag specifies whether map and configure requests on this window should override a x:Substructure-Redirect-Mask on the parent.  You can set the override-redirect flag to #t or #f (default). Window managers use this information to avoid tampering with pop-up windows.

 -- Attribute: x:CW-Save-Under
     Some server implementations may preserve contents of x:Input-Output windows under other x:Input-Output windows.  This is not the same as preserving the contents of a window for you.  You may get better visual appeal if transient windows (for example, pop-up menus) request that the system preserve the screen contents under them, so the temporarily obscured applications do not have to repaint.

     You can set the save-under flag to True or False (default).  If save-under is True, the X server is advised that, when this window is mapped, saving the contents of windows it obscures would be beneficial.

 -- Attribute: x:CW-Event-Mask
     The event mask defines which events the client is interested in for this x:Input-Output or x:Input-Only window (or, for some event types, inferiors of this window).  The event mask is the bitwise inclusive OR of zero or more of the valid event mask bits.  You can specify that no maskable events are reported by setting x:No-Event-Mask (default).

     The following table lists the event mask constants you can pass to the event-mask argument and the circumstances in which you would want to specify the event mask:

     Event Mask
     Circumstances
     x:No-Event-Mask
     No events wanted
     x:Key-Press-Mask
     Keyboard down events wanted
     x:Key-Release-Mask
     Keyboard up events wanted
     x:Button-Press-Mask
     Pointer button down events wanted
     x:Button-Release-Mask
     Pointer button up events wanted
     x:Enter-Window-Mask
     Pointer window entry events wanted
     x:Leave-Window-Mask
     Pointer window leave events wanted
     x:Pointer-Motion-Mask
     Pointer motion events wanted
     x:Pointer-Motion-Hint-Mask

     If x:Pointer-Motion-Hint-Mask is selected in combination with one or
     more motion-masks, the X server is free to send only one x:Motion-Notify
     event (with the is_hint member of the X:Pointer-Moved-Event structure
     set to x:Notify-Hint) to the client for the event window, until either
     the key or button state changes, the pointer leaves the event window, or
     the client calls X:Query-Pointer or X:Get-Motion-Events.  The server
     still may send x:Motion-Notify events without is_hint set to
     x:Notify-Hint.
     x:Button1-Motion-Mask
     Pointer motion while button 1 down
     x:Button2-Motion-Mask
     Pointer motion while button 2 down
     x:Button3-Motion-Mask
     Pointer motion while button 3 down
     x:Button4-Motion-Mask
     Pointer motion while button 4 down
     x:Button5-Motion-Mask
     Pointer motion while button 5 down
     x:Button-Motion-Mask
     Pointer motion while any button down
     x:Keymap-State-Mask
     Keyboard state wanted at window entry and focus in
     x:Exposure-Mask
     Any exposure wanted
     x:Visibility-Change-Mask
     Any change in visibility wanted
     x:Structure-Notify-Mask
     Any change in window structure wanted
     x:Resize-Redirect-Mask
     Redirect resize of this window
     x:Substructure-Notify-Mask
     Substructure notification wanted
     x:Substructure-Redirect-Mask
     Redirect structure requests on children
     x:Focus-Change-Mask
     Any change in input focus wanted
     x:Property-Change-Mask
     Any change in property wanted
     x:Colormap-Change--Mask
     Any change in colormap wanted
     x:Owner-Grab-Button--Mask
     Automatic grabs should activate with owner_events set to True

 -- Attribute: x:CW-Dont-Propagate
     The do-not-propagate-mask attribute defines which events should not be propagated to ancestor windows when no client has the event type selected in this x:Input-Output or x:Input-Only window.  The do-not-propagate-mask is the bitwise inclusive OR of zero or more of the following masks: x:Key-Press, x:Key-Release, x:Button-Press, x:Button-Release, x:Pointer-Motion, x:Button1Motion, x:Button2Motion, x:Button3Motion, x:Button4Motion, x:Button5Motion, and x:Button-Motion. You can specify that all events are propagated by setting x:No-Event-Mask (default).

 -- Attribute: x:CW-Colormap
     The colormap attribute specifies which colormap best reflects the true colors of the x:Input-Output window.  The colormap must have the same visual type as the window.  X servers capable of supporting multiple hardware colormaps can use this information, and window managers can use it for calls to X:Install-Colormap.  You can set the colormap attribute to a colormap or to x:Copy-From-Parent (default).

     If you set the colormap to x:Copy-From-Parent, the parent window's colormap is copied and used by its child.  However, the child window must have the same visual type as the parent.  The parent window must not have a colormap of x:None.  The colormap is copied by sharing the colormap object between the child and parent, not by making a complete copy of the colormap contents.  Subsequent changes to the parent window's colormap attribute do not affect the child window.

 -- Attribute: x:CW-Cursor
     The cursor attribute specifies which cursor is to be used when the pointer is in the x:Input-Output or x:Input-Only window.  You can set the cursor to a cursor or x:None (default).

     If you set the cursor to x:None, the parent's cursor is used when the pointer is in the x:Input-Output or x:Input-Only window, and any change in the parent's cursor will cause an immediate change in the displayed cursor.  On the root window, the default cursor is restored.

 -- Function: x:window-ref window field-name ...
     Returns a list of the components specified by FIELD-NAMEs for the specified WINDOW.  Allowable FIELD-NAMEs are a subset of those for x:window-set!:

       * x:CW-Back-Pixel

       * x:CW-Bit-Gravity

       * x:CW-Win-Gravity

       * x:CW-Backing-Store

       * x:CW-Backing-Planes

       * x:CW-Backing-Pixel

       * x:CW-Override-Redirect

       * x:CW-Save-Under

       * x:CW-Event-Mask

       * x:CW-Dont-Propagate

       * x:CW-Colormap

Window Properties and Visibility
================================

 -- Function: x:get-window-property window property
     Returns the (string or list of numbers) value of PROPERTY of WINDOW.
 -- Function: x:get-window-property window property #t
     Removes and returns the (string or list of numbers) value of PROPERTY of WINDOW.

 -- Function: x:list-properties window
     Returns a list of the properties (strings) defined for WINDOW.

In X parlance, a window which is hidden even when not obscured by other windows is unmapped; one which shows is mapped.  It is an unfortunate name-collision with Scheme, and is ingrained in the attribute names.

 -- Function: x:map-window window
     Maps the WINDOW and all of its subwindows that have had map requests.  Mapping a window that has an unmapped ancestor does not display the window but marks it as eligible for display when the ancestor becomes mapped.  Such a window is called unviewable.  When all its ancestors are mapped, the window becomes viewable and will be visible on the screen if it is not obscured by another window.  This function has no effect if the WINDOW is already mapped.

     If the override-redirect of the window is False and if some other client has selected x:Substructure-Redirect-Mask on the parent window, then the X server generates a MapRequest event, and the x:map-window function does not map the WINDOW.  Otherwise, the WINDOW is mapped, and the X server generates a MapNotify event.

     If the WINDOW becomes viewable and no earlier contents for it are remembered, the X server tiles the WINDOW with its background.  If the window's background is undefined, the existing screen contents are not altered, and the X server generates zero or more x:Expose events.  If backing-store was maintained while the WINDOW was unmapped, no x:Expose events are generated.  If 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.

     If the window is an Input-Output window, x:map-window generates x:Expose events on each Input-Output window that it causes to be displayed. If the client maps and paints the window and if the client begins processing events, the window is painted twice.  To avoid this, first ask for x:Expose events and then map the window, so the client processes input events as usual.  The event list will include x:Expose for each window that has appeared on the screen.  The client's normal response to an x:Expose event should be to repaint the window.  This method usually leads to simpler programs and to proper interaction with window managers.

 -- Function: x:map-subwindows window
     Maps all subwindows of a specified WINDOW in top-to-bottom stacking order.  The X server generates x:Expose events on each newly displayed window.  This may be much more efficient than mapping many windows one at a time because the server needs to perform much of the work only once, for all of the windows, rather than for each window.

 -- Function: x:unmap-window window
     Unmaps the specified WINDOW and causes the X server to generate an UnmapNotify event.  If the specified WINDOW is already unmapped, x:unmap-window has no effect.  Normal exposure processing on formerly obscured windows is performed.  Any child window will no longer be visible until another map call is made on the parent.  In other words, the subwindows are still mapped but are not visible until the parent is mapped.  Unmapping a WINDOW will generate x:Expose events on windows that were formerly obscured by it.

 -- Function: x:unmap-subwindows window
     Unmaps all subwindows for the specified WINDOW in bottom-to-top stacking order.  It causes the X server to generate an UnmapNotify event on each subwindow and x:Expose events on formerly obscured windows.  Using this function is much more efficient than unmapping multiple windows one at a time because the server needs to perform much of the work only once, for all of the windows, rather than for each window.

Graphics Context
****************

Most attributes of graphics operations are stored in GCs.  These include line width, line style, plane mask, foreground, background, tile, stipple, clipping region, end style, join style, and so on. Graphics operations (for example, drawing lines) use these values to determine the actual drawing operation.

 -- Function: x:create-gc drawable field-name value ...
     Creates and returns graphics context.  The graphics context can be used with any destination drawable having the same root and depth as the specified DRAWABLE.

 -- Function: x:gc-set! graphics-context field-name value ...
     Changes the components specified by FIELD-NAMEs for the specified GRAPHICS-CONTEXT.  The restrictions are the same as for x:create-gc.  The order in which components are verified and altered is server dependent.  If an error occurs, a subset of the components may have been altered.

 -- Function: x:copy-gc-fields! gcontext-src gcontext-dst field-name ...
     Copies the components specified by FIELD-NAMEs from GCONTEXT-SRC to GCONTEXT-DST.  GCONTEXT-SRC and GCONTEXT-DST must have the same root and depth.

 -- Function: x:gc-ref graphics-context field-name ...
     Returns a list of the components specified by FIELD-NAMEs ... from the specified GRAPHICS-CONTEXT.

GC Attributes
=============

Both x:create-gc and x:change-gc take one argument followed by pairs of arguments, where the first is one of the property-name symbols (or its top-level value) listed below; and the second is the value to associate with that property.

 -- Attribute: x:GC-Function
     The function attributes of a GC are used when you update a section of a drawable (the destination) with bits from somewhere else (the source). The function in a GC defines how the new destination bits are to be computed from the source bits and the old destination bits.  x:G-Xcopy is typically the most useful because it will work on a color display, but special applications may use other functions, particularly in concert with particular planes of a color display.  The 16 functions are:

          x:G-Xclear           0
          x:G-Xand             (AND src dst)
          x:G-Xand-Reverse     (AND src (NOT dst))
          x:G-Xcopy            src
          x:G-Xand-Inverted    (AND (NOT src) dst)
          x:G-Xnoop            dst
          x:G-Xxor             (XOR src dst)
          x:G-Xor              (OR src dst)
          x:G-Xnor             (AND (NOT src) (NOT dst))
          x:G-Xequiv           (XOR (NOT src) dst)
          x:G-Xinvert          (NOT dst)
          x:G-Xor-Reverse      (OR src (NOT dst))
          x:G-Xcopy-Inverted   (NOT src)
          x:G-Xor-Inverted     (OR (NOT src) dst)
          x:G-Xnand            (OR (NOT src) (NOT dst))
          x:G-Xset             1

 -- Attribute: x:GC-Plane-Mask

     Many graphics operations depend on either pixel values or planes in a GC.  The planes attribute is an integer which specifies which planes of the destination are to be modified, one bit per plane.  A monochrome display has only one plane and will be the least significant bit of the integer.  As planes are added to the display hardware, they will occupy more significant bits in the plane mask.

     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.  x:All-Planes can be used to refer to all planes of the screen simultaneously.  The result is computed by the following:

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

     Range checking is not performed on a plane-mask value.  It is simply truncated to the appropriate number of bits.

 -- Attribute: x:GC-Foreground
 -- Attribute: x:GC-Background
     Range checking is not performed on the values for foreground or background.  They are simply truncated to the appropriate number of bits.

     Note that foreground and background are not initialized to any values likely to be useful in a window.

 -- Attribute: x:GC-Line-Width
     The line-width is measured in pixels and either can be greater than or equal to one (wide line) or can be the special value zero (thin line).

     Thin lines (zero line-width) are one-pixel-wide lines drawn using an unspecified, device-dependent algorithm.  There are only two constraints on this algorithm.

       * If a line is drawn unclipped from [x1,y1] to [x2,y2] and if another line is drawn unclipped from [x1+dx,y1+dy] to [x2+dx,y2+dy], 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.

       * 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.

     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-style and join-style.  It is recommended that this property be true for thin lines, but this is not required.  A line-width of zero may differ from a line-width of one in which pixels are drawn.  This permits the use of many manufacturers' line drawing hardware, which may run many times faster than the more precisely specified wide lines.

     In general, drawing a thin line will be faster than drawing a wide line of width one.  However, because of their different drawing algorithms, thin lines may not mix well aesthetically with wide lines.  If it is desirable to obtain precise and uniform results across all displays, a client should always use a line-width of one rather than a linewidth of zero.

 -- Attribute: x:GC-Line-Style
     The line-style defines which sections of a line are drawn:

     x:Line-Solid
          The full path of the line is drawn.

     x:Line-Double-Dash
          The full path of the line is drawn, but the even dashes are filled differently from the odd dashes (see fill-style) with x:Cap-Butt style used where even and odd dashes meet.

     x:Line-On-Off-Dash
          Only the even dashes are drawn, and cap-style applies to all internal ends of the individual dashes, except x:Cap-Not-Last is treated as x:Cap-Butt.

 -- Attribute: x:GC-Cap-Style

     The cap-style defines how the endpoints of a path are drawn:

     x:Cap-Not-Last
          This is equivalent to x:Cap-Butt except that for a line-width of zero the final endpoint is not drawn.

     x:Cap-Butt
          The line is square at the endpoint (perpendicular to the slope of the line) with no projection beyond.

     x:Cap-Round
          The line has a circular arc with the diameter equal to the line-width, centered on the endpoint.  (This is equivalent to x:Cap-Butt for line-width of zero).

     x:Cap-Projecting
          The line is square at the end, but the path continues beyond the endpoint for a distance equal to half the line-width.  (This is equivalent to x:Cap-Butt for line-width of zero).

 -- Attribute: x:GC-Join-Style

     The join-style defines how corners are drawn for wide lines:

     x:Join-Miter
          The outer edges of two lines extend to meet at an angle.  However, if the angle is less than 11 degrees, then a x:Join-Bevel join-style is used instead.

     x:Join-Round
          The corner is a circular arc with the diameter equal to the line-width, centered on the x:Join-point.

     x:Join-Bevel
          The corner has x:Cap-Butt endpoint styles with the triangular notch filled.

 -- Attribute: x:GC-Fill-Style

     The fill-style defines the contents of the source for line, text, and fill requests.  For all text and fill requests (for example, X:Draw-Text, X:Fill-Rectangle, X:Fill-Polygon, and X:Fill-Arc); for line requests with linestyle x:Line-Solid (for example, X:Draw-Line, X:Draw-Segments, X:Draw-Rectangle, X:Draw-Arc); and for the even dashes for line requests with line-style x:Line-On-Off-Dash or x:Line-Double-Dash, the following apply:

     x:Fill-Solid
          Foreground

     x:Fill-Tiled
          Tile

     x:Fill-Opaque-Stippled
          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

     x:Fill-Stippled
          Foreground masked by stipple

     When drawing lines with line-style x:Line-Double-Dash, the odd dashes are controlled by the fill-style in the following manner:

     x:Fill-Solid
          Background

     x:Fill-Tiled
          Same as for even dashes

     x:Fill-Opaque-Stippled
          Same as for even dashes

     x:Fill-Stippled
          Background masked by stipple

 -- Attribute: x:GC-Fill-Rule
     The fill-rule defines what pixels are inside (drawn) for paths given in X:Fill-Polygon requests and can be set to x:Even-Odd-Rule or x:Winding-Rule.

     x:Even-Odd-Rule
          A point is inside if an infinite ray with the point as origin crosses the path an odd number of times.

     x:Winding-Rule
          A point is inside if an infinite ray with the point as origin crosses an unequal number of clockwise and counterclockwise directed path segments.

     A clockwise directed path segment is one that crosses the ray from left to right as observed from the point.  A counterclockwise segment is one that crosses the ray from right to left as observed from the point.  The case where a directed line segment is coincident with the ray is uninteresting because you can simply choose a different ray that is not coincident with a segment.

     For both x:Even-Odd-Rule and x:Winding-Rule, 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 on a horizontal edge are a special case and are inside if and only if the polygon interior is immediately below (y increasing direction).

 -- Attribute: x:GC-Tile
 -- Attribute: x:GC-Stipple
     The tile/stipple represents an infinite two-dimensional plane, with the tile/stipple replicated in all dimensions.

     The tile pixmap must have the same root and depth as the GC, or an error results.  The stipple pixmap must have depth one and must have the same root as the GC, or an error results.  For stipple operations where the fill-style is x:Fill-Stippled but not x:Fill-Opaque-Stippled, the stipple pattern is tiled in a single plane and acts as an additional clip mask to be ANDed with the clip-mask.  Although some sizes may be faster to use than others, any size pixmap can be used for tiling or stippling.

 -- Attribute: x:GC-Tile-Stip-X-Origin
 -- Attribute: x:GC-Tile-Stip-Y-Origin
     When the tile/stipple plane is superimposed on a drawable for use in a graphics operation, the upper-left corner of some instance of the tile/stipple is at the coordinates within the drawable specified by the tile/stipple origin.  The tile/stipple origin is interpreted relative to the origin of whatever destination drawable is specified in a graphics request.

 -- Attribute: x:GC-Font
     The font to be used for drawing text.

 -- Attribute: x:GC-Subwindow-Mode
     You can set the subwindow-mode to x:Clip-By-Children or x:Include-Inferiors.

     x:Clip-By-Children
          Both source and destination windows are additionally clipped by all viewable Input-Output children.

     x:Include-Inferiors
          Neither source nor destination window is clipped by inferiors.  This will result in including subwindow contents in the source and drawing through subwindow boundaries of the destination.  The use of x:Include-Inferiors on a window of one depth with mapped inferiors of differing depth is not illegal, but the semantics are undefined by the core protocol.

 -- Attribute: x:GC-Graphics-Exposures
     The graphics-exposure flag controls x:Graphics-Expose event generation for X:Copy-Area and X:Copy-Plane requests (and any similar requests defined by extensions).

 -- Attribute: x:GC-Clip-X-Origin
 -- Attribute: x:GC-Clip-Y-Origin
     The clip-mask origin is interpreted relative to the origin of whatever destination drawable is specified in a graphics request.

 -- Attribute: x:GC-Clip-Mask
     The clip-mask restricts writes to the destination drawable.  If the clip-mask is set to a pixmap, it must have depth one and have the same root as the GC, or an error results.  If clip-mask is set to x:None, the pixels are always drawn regardless of the clip origin. The clip-mask also can be set by calling X:Set-Region.  Only pixels where the clip-mask has a bit set to 1 are drawn.  Pixels are not drawn outside the area covered by the clip-mask or where the clip-mask has a bit set to 0.  The clip-mask 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.

 -- Attribute: x:GC-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 elements combined with a join-style but is reset to the dash-offset between each sequence of joined lines.

     The unit of measure for dashes is the same for the ordinary coordinate system.  Ideally, a dash length is measured along the slope of the line, but implementations are only required to match this ideal for horizontal and vertical lines. Failing the ideal semantics, it is suggested that the length be measured along the major axis of the line.  The major axis is defined as the x axis for lines drawn at an angle of between -45 and +45 degrees or between 135 and 225 degrees from the x axis.  For all other lines, the major axis is the y axis.

 -- Attribute: x:GC-Dash-List
     There must be at least one element in the specified DASH-LIST. The initial and alternating elements (second, fourth, and so on) of the DASH-LIST are the even dashes, and the others are the odd dashes. Each element specifies a dash length in pixels.  All of the elements must be nonzero.  Specifying an odd-length list is equivalent to specifying the same list concatenated with itself to produce an even-length list.

 -- Attribute: x:GC-Arc-Mode
     The arc-mode controls filling in the X:Fill-Arcs function and can be set to x:Arc-Pie-Slice or x:Arc-Chord.

     x:Arc-Pie-Slice
          The arcs are pie-slice filled.

     x:Arc-Chord
          The arcs are chord filled.

Cursor
******

 -- Function: x:create-cursor display shape
     X provides a set of standard cursor shapes in a special font named cursor.  Applications are encouraged to use this interface for their cursors because the font can be customized for the individual display type.  The SHAPE argument specifies which glyph of the standard fonts to use.

     The hotspot comes from the information stored in the cursor font.  The initial colors of a cursor are a black foreground and a white background (see X:Recolor-Cursor).  The names of all cursor shapes are defined with the prefix XC: in x11.scm.

 -- Function: x:create-cursor source-font source-char mask-font mask-char fgc bgc
     Creates a cursor from the source and mask bitmaps obtained from the specified font glyphs.  The integer SOURCE-CHAR must be a defined glyph in SOURCE-FONT.  The integer MASK-CHAR must be a defined glyph in MASK-FONT.  The origins of the SOURCE-CHAR and MASK-CHAR glyphs are positioned coincidently and define the hotspot.  The SOURCE-CHAR and MASK-CHAR need not have the same bounding box metrics, and there is no restriction on the placement of the hotspot relative to the bounding boxes.

 -- Function: x:create-cursor source-font source-char #f #f fgc bgc
     If MASK-FONT and MASK-CHAR are #f, all pixels of the source are displayed.

 -- Function: x:create-cursor source-pixmap mask-pixmap fgc bgc origin
     MASK-PIXMAP must be the same size as the pixmap defined by the SOURCE-PIXMAP argument.  The foreground and background RGB values must be specified using FOREGROUND-COLOR and BACKGROUND-COLOR, even if the X server only has a x:Static-Gray or x:Gray-Scale screen.  The hotspot must be a point within the SOURCE-PIXMAP.

     X:Create-Cursor creates and returns a cursor.  The FOREGROUND-COLOR is used for the pixels set to 1 in the source, and the BACKGROUND-COLOR is used for the pixels set to 0.  Both source and mask must have depth one but can have any root.  The MASK-PIXMAP defines the shape of the cursor.  The pixels set to 1 in MASK-PIXMAP define which source pixels are displayed, and the pixels set to 0 define which pixels are ignored.

 -- Function: x:create-cursor source-pixmap #f fgc bgc origin
     If MASK-PIXMAP is #f, all pixels of the source are displayed.

Colormap
********

A colormap maps pixel values to RGB color space values.

 -- Function: x:create-colormap window visual alloc-policy
     WINDOW specifies the window on whose screen you want to create a colormap.  VISUAL specifies a visual type supported on the screen. ALLOC-POLICY Specifies the colormap entries to be allocated.  You can pass X:Alloc-None or X:Alloc-All.

     The X:Create-Colormap function creates and returns a colormap of the specified VISUAL type for the screen on which WINDOW resides.  Note that WINDOW is used only to determine the screen.

     X:Gray-Scale

     X:Pseudo-Color

     X:Direct-Color
          The initial values of the colormap entries are undefined.

     X:Static-Gray

     X:Static-Color

     X:True-Color
          The entries have defined values, but those values are specific to VISUAL and are not defined by X.  The ALLOC-POLICY must be X:Alloc-None.

     For the other visual classes, if ALLOC-POLICY is X:Alloc-None, the colormap initially has no allocated entries, and clients can allocate them.

     If ALLOC-POLICY is X:Alloc-All, the entire colormap is allocated writable.  The initial values of all allocated entries are undefined.

     X:Gray-Scale

     X:Pseudo-Color
          The effect is as if an XAllocColorCells call returned all pixel values from zero to N - 1, where N is the colormap entries value in VISUAL.

     X:Direct-Color
          The effect is as if an XAllocColorPlanes call returned a pixel value of zero and red_mask, green_mask, and blue_mask values containing the same bits as the corresponding masks in the specified visual.

To create a new colormap when the allocation out of a previously shared colormap has failed because of resource exhaustion, use:

 -- Function: x:copy-colormap-and-free colormap

     Creates and returns a colormap of the same visual type and for the same screen as the specified COLORMAP.  It also moves all of the client's existing allocation from the specified COLORMAP to the new colormap with their color values intact and their read-only or writable characteristics intact and frees those entries in the specified colormap.  Color values in other entries in the new colormap are undefined.  If the specified colormap was created by the client with alloc set to X:Alloc-All, the new colormap is also created with X:Alloc-All, all color values for all entries are copied from the specified COLORMAP, and then all entries in the specified COLORMAP are freed.  If the specified COLORMAP was not created by the client with X:Alloc-All, the allocations to be moved are all those pixels and planes that have been allocated by the client and that have not been freed since they were allocated.

A colormap maps pixel values to elements of the RGB datatype.  An RGB is a list or vector of 3 integers, describing the red, green, and blue intensities respectively.  The integers are in the range 0 - 65535.

 -- Function: x:alloc-colormap-cells colormap ncolors nplanes
 -- Function: x:alloc-colormap-cells colormap ncolors nplanes contiguous?

     The X:Alloc-Color-Cells function allocates read/write color cells.  The number of colors, NCOLORS must be positive and the number of planes, NPLANES nonnegative.  If NCOLORS and nplanes are requested, then NCOLORS pixels and nplane plane masks are returned.  No mask will have any bits set to 1 in common with any other mask or with any of the pixels.  By ORing together each pixel with zero or more masks, NCOLORS * 2^NPLANES distinct pixels can be produced.  All of these are allocated writable by the request.

     x:Gray-Scale

     x:Pseudo-Color
          Each mask has exactly one bit set to 1.  If CONTIGUOUS? is non-false and if all masks are ORed together, a single contiguous set of bits set to 1 is formed.

     x:Direct-Color
          Each mask has exactly three bits set to 1.  If CONTIGUOUS? is non-false and if all masks are ORed together, three contiguous sets of bits set to 1 (one within each pixel subfield) is formed.

     The RGB values of the allocated entries are undefined. X:Alloc-Color-Cells returns a list of two uniform arrays if it succeeded or #f if it failed.  The first array has the pixels allocated and the second has the plane-masks.

 -- Function: x:alloc-colormap-cells colormap ncolors rgb
 -- Function: x:alloc-colormap-cells colormap ncolors rgb contiguous?

     The specified NCOLORS must be positive; and RGB a list or vector of 3 nonnegative integers.  If NCOLORS colors, NREDS reds, NGREENS greens, and NBLUES blues are requested, NCOLORS pixels are returned; and the masks have NREDS, NGREENS, and NBLUES bits set to 1, respectively.  If CONTIGUOUS?  is non-false, each mask will have a contiguous set of bits set to 1.  No mask will have any bits set to 1 in common with any other mask or with any of the pixels.

     Each mask will lie within the corresponding pixel subfield.  By ORing together subsets of masks with each pixel value, NCOLORS * 2(NREDS+NGREENS+NBLUES) distinct pixel values can be produced.  All of these are allocated by the request.  However, in the colormap, there are only NCOLORS * 2^NREDS independent red entries, NCOLORS * 2^NGREENS independent green entries, and NCOLORS * 2^NBLUES independent blue entries.

     X:Alloc-Color-Cells returns a list if it succeeded or #f if it failed.  The first element of the list has an array of the pixels allocated.  The second, third, and fourth elements are the red, green, and blue plane-masks.

 -- Function: x:free-colormap-cells colormap pixels planes
 -- Function: x:free-colormap-cells colormap pixels

     Frees the cells represented by pixels whose values are in the PIXELS unsigned-integer uniform-vector.  The PLANES argument should not have any bits set to 1 in common with any of the pixels.  The set of all pixels is produced by ORing together subsets of the PLANES argument with the pixels.  The request frees all of these pixels that were allocated by the client.  Note that freeing an individual pixel obtained from X:Alloc-Colormap-Cells with a planes argument may not actually allow it to be reused until all of its related pixels are also freed.  Similarly, a read-only entry is not actually freed until it has been freed by all clients, and if a client allocates the same read-only entry multiple times, it must free the entry that many times before the entry is actually freed.

     All specified pixels that are allocated by the client in the COLORMAP are freed, even if one or more pixels produce an error. It is an error if a specified pixel is not allocated by the client (that is, is unallocated or is only allocated by another client) or if the colormap was created with all entries writable (by passing x:Alloc-All to X:Create-Colormap).  If more than one pixel is in error, the one that gets reported is arbitrary.

 -- Function: x:colormap-find-color colormap rgb

     RGB is a list or vector of 3 integers, describing the red, green, and blue intensities respectively; or an integer #xrrggbb, packing red, green and blue intensities in the range 0 - 255.

 -- Function: x:colormap-find-color colormap color-name

     The case-insensitive string COLOR_NAME specifies the name of a color (for example, red)

     X:Colormap-Find-Color allocates a read-only colormap entry corresponding to the closest RGB value supported by the hardware. X:Colormap-Find-Color returns the pixel value of the color closest to the specified RGB or COLOR_NAME elements supported by the hardware, if successful; otherwise X:Colormap-Find-Color returns #f.

     Multiple clients that request the same effective RGB value can be assigned the same read-only entry, thus allowing entries to be shared.  When the last client deallocates a shared cell, it is deallocated.

 -- Function: x:color-ref colormap pixel

     Returns a list of 3 integers, describing the red, green, and blue intensities respectively of the COLORMAP entry of the cell indexed by PIXEL.

     The integer PIXEL must be a valid index into COLORMAP.

 -- Function: X:Color-Set! colormap pixel rgb

     RGB is a list or vector of 3 integers, describing the red, green, and blue intensities respectively; or an integer #xrrggbb, packing red, green and blue intensities in the range 0 - 255.

 -- Function: X:Color-Set! colormap pixel color-name

     The case-insensitive string COLOR_NAME specifies the name of a color (for example, red)

     The integer PIXEL must be a valid index into COLORMAP.

     X:Color-Set! changes the COLORMAP entry of the read/write cell indexed by PIXEL.  If the COLORMAP is an installed map for its screen, the changes are visible immediately.

 -- Function: x:install-colormap colormap

     Installs the specified COLORMAP for its associated screen.  All windows associated with COLORMAP immediately display with true colors.  A colormap is associated with a window when the window is created or its attributes changed.

     If the specified colormap is not already an installed colormap, the X server generates a ColormapNotify event on each window that has that colormap.

 -- Function: x:ccc colormap
     Returns the Color-Conversion-Context of COLORMAP.

Rendering
*********

 -- Function: x:flush display
 -- Function: x:flush window
     Flushes the output buffer.  Some client applications need not use this function because the output buffer is automatically flushed as needed by calls to X:Pending, X:Next-Event, and X:Window-Event.  Events generated by the server may be enqueued into the library's event queue.

 -- Function: x:flush gc
     Forces sending of GC component changes.

     Xlib usually defers sending changes to the components of a GC to the server until a graphics function is actually called with that GC.  This permits batching of component changes into a single server request.  In some circumstances, however, it may be necessary for the client to explicitly force sending the changes to the server.  An example might be when a protocol extension uses the GC indirectly, in such a way that the extension interface cannot know what GC will be used.

 -- Function: x:clear-area window (x-pos y-pos) (width height) expose?
     Paints a rectangular area in the specified WINDOW according to the specified dimensions with the WINDOW's background pixel or pixmap. The subwindow-mode effectively is x:Clip-By-Children.  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 clipped by any children is filled with this tile. If the WINDOW has background x:None, the contents of the WINDOW are not changed.  In either case, if EXPOSE? is True, one or more x:Expose events are generated for regions of the rectangle that are either visible or are being retained in a backing store.  If you specify a WINDOW whose class is x:Input-Only, an error results.

 -- Function: x:fill-rectangle window gcontext position size

Draw Strings
============

 -- Function: x:draw-string drawable gc position string
     POSITION specifies coordinates relative to the origin of DRAWABLE of the origin of the first character to be drawn.

     x:draw-string draws the characters of STRING, starting at POSITION.

 -- Function: x:image-string drawable gc position string
     POSITION specifies coordinates relative to the origin of DRAWABLE of the origin of the first character to be drawn.

     x:image-string draws the characters and background of STRING, starting at POSITION.

Draw Shapes
===========

 -- Function: x:draw-points drawable gc position ...
     POSITION ... specifies coordinates of the point to be drawn.

 -- Function: x:draw-points drawable gc x y ...
     (X, Y) ... specifies coordinates of the point to be drawn.

 -- Function: x:draw-points drawable gc point-array
     POINT-ARRAY is a uniform short array of rank 2, whose rightmost index spans a range of 2.

     The X:Draw-Points procedure uses the foreground pixel and function components of the GC to draw points into DRAWABLE at the positions (relative to the origin of DRAWABLE) specified.

     X:Draw-Points uses these GC components: function, planemask, foreground, subwindow-mode, clip-x-origin, clip-y-origin, and clip-mask.

 -- Function: x:draw-segments drawable gc pos1 pos2 ...
     POS1, POS2, ... specify coordinates to be connected by segments.

 -- Function: x:draw-segments drawable gc x1 y1 x2 y2 ...
     (X1, Y1), (X2, Y2) ... specify coordinates to be connected by segments.

 -- Function: x:draw-segments drawable gc point-array
     POINT-ARRAY is a uniform short array of rank 2, whose rightmost index spans a range of 2.

     The X:Draw-Segments procedure uses the components of the specified GC to draw multiple unconnected lines between disjoint adjacent pair of points passed as arguments.  It draws the segments in order and does not perform joining at coincident endpoints.  For any given line, X:Draw-Segments does not draw a pixel more than once. If thin (zero line-width) segments intersect, the intersecting pixels are drawn multiple times.  If wide segments intersect, the intersecting pixels are drawn only once, as though the entire PolyLine protocol request were a single, filled shape.  X:Draw-Segments treats all coordinates as relative to the origin of DRAWABLE.

     X:Draw-Segments uses these GC components: function, plane-mask, line-width, line-style, cap-style, fill-style, subwindow-mode, clip-x-origin, clip-y-origin, and clip-mask, join-style. It also use these GC mode-dependent components: foreground, background, tile, stipple, tilestipple-x-origin, tile-stipple-y-origin, dash-offset, and dash-list.

 -- Function: x:draw-lines drawable gc pos1 pos2 ...
     POS1, POS2, ... specify coordinates to be connected by lines.

 -- Function: x:draw-lines drawable gc x1 y1 x2 y2 ...
     (X1, Y1), (X2, Y2) ... specify coordinates to be connected by lines.

 -- Function: x:draw-lines drawable gc point-array
     POINT-ARRAY is a uniform short array of rank 2, whose rightmost index spans a range of 2.

     The X:Draw-Lines procedure uses the components of the specified GC to draw lines between each adjacent pair of points passed as arguments.  It draws the lines in order.  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, X:Draw-Lines does not draw a pixel 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 protocol request were a single, filled shape.  X:Draw-Lines treats all coordinates as relative to the origin of DRAWABLE.

     X:Draw-Lines uses these GC components: function, plane-mask, line-width, line-style, cap-style, fill-style, subwindow-mode, clip-x-origin, clip-y-origin, and clip-mask, join-style. It also use these GC mode-dependent components: foreground, background, tile, stipple, tilestipple-x-origin, tile-stipple-y-origin, dash-offset, and dash-list.

 -- Function: x:fill-polygon drawable gc pos1 pos2 ...
     POS1, POS2, ... specify coordinates of the border path.

 -- Function: x:fill-polygon drawable gc x1 y1 x2 y2 ...
     (X1, Y1), (X2, Y2) ... specify coordinates of the border path.

 -- Function: x:fill-polygon drawable gc point-array
     POINT-ARRAY is a uniform short array of rank 2, whose rightmost index spans a range of 2.

     The path is closed automatically if the last point in the list or POINT-ARRAY does not coincide with the first point.

     The X:Fill-Polygon procedure uses the components of the specified GC to fill the region closed by the specified path. X:Fill-Polygon does not draw a pixel of the region more than once.  X:Fill-Polygon treats all coordinates as relative to the origin of DRAWABLE.

     X:Fill-Polygon uses these GC components: function, planemask, fill-style, fill-rule, subwindow-mode, clip-x-origin, clip-y-origin, and clip-mask.  It also use these GC mode-dependent components: foreground, background, tile, stipple, tile-stipple-x-origin, and tile-stipple-y-origin.

Images
******

 -- Function: x:read-bitmap-file drawable file

Event
*****

These three status routines always return immediately if there are events already in the queue.

 -- Function: x:q-length display
     Returns the length of the event queue for the connected DISPLAY. Note that there may be more events that have not been read into the queue yet (see X:Events-Queued).

 -- Function: x:pending display
     Returns the number of events that have been received from the X server but have not been removed from the event queue.

 -- Function: x:events-queued display
     Returns the number of events already in the queue if the number is nonzero.  If there are no events in the queue, X:Events-Queued attempts to read more events out of the application's connection without flushing the output buffer and returns the number read.

Both of these routines return an object of type event.

 -- Function: x:next-event display
     Removes and returns the first event from the event queue.  If the event queue is empty, X:Next-Event flushes the output buffer and blocks until an event is received.

 -- Function: x:peek-event display
     Returns the first event from the event queue, but it does not remove the event from the queue.  If the queue is empty, X:Peek-Event flushes the output buffer and blocks until an event is received.

Each event object has fields dependent on its sub-type.

 -- Function: x:event-ref event field-name

     window

     The window on which EVENT was generated and is referred to as the
     event window.
     root

     is the event window's root window.
     subwindow

     If the source window is an inferior of the event window, the
     SUBWINDOW is the child of the event window that is the source
     window or the child of the event window that is an ancestor of the
     source window.  Otherwise, None.
     X-event:type

     An integer: X:KEY-PRESS, X:KEY-RELEASE,
     X:BUTTON-PRESS, X:BUTTON-RELEASE, X:MOTION-NOTIFY,
     X:ENTER-NOTIFY, X:LEAVE-NOTIFY, X:FOCUS-IN,
     X:FOCUS-OUT, X:KEYMAP-NOTIFY, X:EXPOSE,
     X:GRAPHICS-EXPOSE, X:NO-EXPOSE, X:VISIBILITY-NOTIFY,
     X:CREATE-NOTIFY, X:DESTROY-NOTIFY, X:UNMAP-NOTIFY,
     X:MAP-NOTIFY, X:MAP-REQUEST, X:REPARENT-NOTIFY,
     X:CONFIGURE-NOTIFY, X:CONFIGURE-REQUEST,
     X:GRAVITY-NOTIFY, X:RESIZE-REQUEST,
     X:CIRCULATE-NOTIFY, X:CIRCULATE-REQUEST,
     X:PROPERTY-NOTIFY, X:SELECTION-CLEAR,
     X:SELECTION-REQUEST, X:SELECTION-NOTIFY,
     X:COLORMAP-NOTIFY, X:CLIENT-MESSAGE, or
     X:MAPPING-NOTIFY.
     X-event:serial

     The serial number of the protocol request that generated the EVENT.
     X-event:send-event

     Boolean that indicates whether the event was sent by a different client.
     X-event:time

     The time when the EVENT was generated expressed in milliseconds.
     X-event:x
     X-event:y

     For window entry/exit events the X and Y members are set to
     the coordinates of the pointer position in the event window.  This
     position is always the pointer's final position, not its initial
     position.  If the event window is on the same screen as the root window,
     X and Y are the pointer coordinates relative to the event
     window's origin.  Otherwise, X and Y are set to zero.

     For expose events The X and Y members are set to the
     coordinates relative to the drawable's origin and indicate the
     upper-left corner of the rectangle.

     For configure, create, gravity, and reparent events the X and
     Y members are set to the window's coordinates relative to the
     parent window's origin and indicate the position of the upper-left
     outside corner of the created window.
     X-event:x-root
     X-event:y-root

     The pointer's coordinates relative to the root window's origin at the
     time of the EVENT.
     X-event:state

     For keyboard, pointer and window entry/exit events, the state member is
     set to indicate the logical state of the pointer buttons and modifier
     keys just prior to the EVENT, which is the bitwise inclusive OR of
     one or more of the button or modifier key masks: X:BUTTON1-MASK,
     X:BUTTON2-MASK, X:BUTTON3-MASK, X:BUTTON4-MASK,
     X:BUTTON5-MASK, X:SHIFT-MASK, X:LOCK-MASK,
     X:CONTROL-MASK, X:MOD1-MASK, X:MOD2-MASK,
     X:MOD3-MASK, X:MOD4-MASK, and X:MOD5-MASK.

     For visibility events, the state of the window's visibility:
     X:VISIBILITY-UNOBSCURED, X:VISIBILITY-PARTIALLY-OBSCURED, or
     X:VISIBILITY-FULLY-OBSCURED.

     For colormap events, indicates whether the colormap is installed or
     uninstalled: x:Colormap-Installed or x:Colormap-Uninstalled.

     For property events, indicates whether the property was changed to a new
     value or deleted: x:Property-New-Value or x:Property-Delete.
     X-event:keycode

     An integer that represents a physical key on the keyboard.
     X-event:same-screen

     Indicates whether the event window is on the same screen as the root
     window.  If #t, the event and root windows are on the same screen.  If
     #f, the event and root windows are not on the same screen.
     X-event:button

     The pointer button that changed state; can be the X:BUTTON1,
     X:BUTTON2, X:BUTTON3, X:BUTTON4, or X:BUTTON5
     value.
     X-event:is-hint

     Detail of motion-notify events: X:NOTIFY-NORMAL or
     X:NOTIFY-HINT.
     X-event:mode

     Indicates whether the EVENT is a normal event, pseudo-motion event
     when a grab activates, or a pseudo-motion event when a grab deactivates:
     X:NOTIFY-NORMAL, X:NOTIFY-GRAB, or X:NOTIFY-UNGRAB.
     X-event:detail

     Indicates the notification detail: X:NOTIFY-ANCESTOR,
     X:NOTIFY-VIRTUAL, X:NOTIFY-INFERIOR,
     X:NOTIFY-NONLINEAR, or X:NOTIFY-NONLINEAR-VIRTUAL.
     X-event:focus

     If the event window is the focus window or an inferior of the focus
     window, #t; otherwise #f.
     X-event:width
     X-event:height

     The size (extent) of the rectangle.
     X-event:count

     For mapping events is the number of keycodes altered.

     For expose events Is the number of Expose or GraphicsExpose events that
     are to follow.  If count is zero, no more Expose events follow for this
     window.  However, if count is nonzero, at least that number of Expose
     events (and possibly more) follow for this window.  Simple applications
     that do not want to optimize redisplay by distinguishing between
     subareas of its window can just ignore all Expose events with nonzero
     counts and perform full redisplays on events with zero counts.
     X-event:major-code

     The major_code member is set to the graphics request initiated by the
     client and can be either X_CopyArea or X_CopyPlane.  If it is
     X_CopyArea, a call to XCopyArea initiated the request.  If it is
     X_CopyPlane, a call to XCopyPlane initiated the request.
     X-event:minor-code

     Not currently used.
     X-event:border-width

     For configure events, the width of the window's border, in pixels.
     X-event:override-redirect

     The override-redirect attribute of the window.  Window manager clients
     normally should ignore this window if it is #t.
     X-event:from-configure

     True if the event was generated as a result of a resizing of the
     window's parent when the window itself had a win-gravity of
     x:Unmap-Gravity.
     X-event:value-mask

     Indicates which components were specified in the ConfigureWindow
     protocol request.  The corresponding values are reported as given in the
     request.  The remaining values are filled in from the current geometry
     of the window, except in the case of above (sibling) and detail
     (stack-mode), which are reported as None and Above, respectively, if
     they are not given in the request.
     X-event:place

     The window's position after the restack occurs and is either
     x:Place-On-Top or x:Place-On-Bottom.  If it is x:Place-On-Top, the
     window is now on top of all siblings.  If it is x:Place-On-Bottom, the
     window is now below all siblings.
     X-event:new

     indicate whether the colormap for the specified window was changed or
     installed or uninstalled and can be True or False.  If it is True, the
     colormap was changed.  If it is False, the colormap was installed or
     uninstalled.
     X-event:format

     Is 8, 16, or 32 and specifies whether the data should be viewed as a
     list of bytes, shorts, or longs
     X-event:request

     Indicates the kind of mapping change that occurred and can be
     X:MAPPING-MODIFIER, X:MAPPING-KEYBOARD, or
     X:MAPPING-POINTER.  If it is X:MAPPING-MODIFIER, the
     modifier mapping was changed.  If it is X:MAPPING-KEYBOARD, the
     keyboard mapping was changed.  If it is X:MAPPING-POINTER, the
     pointer button mapping was changed.
     X-event:first-keycode

     The X-event:first-keycode is set only if the X-event:request was set to
     X:MAPPING-KEYBOARD.  The number in X-event:first-keycode
     represents the first number in the range of the altered mapping, and
     X-event:count represents the number of keycodes altered.

Indexes
*******