\input texinfo @c -*-texinfo-*-
@c %**start of header
@setfilename Xlibscm.info
@settitle Xlibscm
@include version.txi
@setchapternewpage on
@c Choices for setchapternewpage are {on,off,odd}.
@paragraphindent 0
@defcodeindex ft
@syncodeindex ft cp
@c %**end of header

@dircategory The Algorithmic Language Scheme
@direntry
* Xlibscm: (Xlibscm).   SCM Language X Interface.
@end direntry

@iftex
@finalout
@c DL: lose the egregious vertical whitespace, esp. around examples
@c but paras in @defun-like things don't have parindent
@parskip 4pt plus 1pt
@end iftex

@titlepage
@title Xlibscm
@subtitle SCM Language X Interface
@subtitle Version @value{SCMVERSION}
@author by Aubrey Jaffer

@page
@vskip 0pt plus 1filll
Copyright @copyright{} 1990-1999 Free Software Foundation

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.
@end titlepage

@node Top, Xlibscm, (dir), (dir)


@ifinfo
This manual documents the X - SCM Language X Interface.  The most recent
information about SCM can be found on SCM's @dfn{WWW} home page:

@center @url{http://swissnet.ai.mit.edu/~jaffer/SCM.html}


Copyright (C) 1990-1999 Free Software Foundation

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.

@ignore
Permission is granted to process this file through TeX and print the
results, provided the printed document carries copying permission
notice identical to this one except for the removal of this paragraph
(this paragraph not being relevant to the printed manual).

@end ignore
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.
@end ifinfo

@menu
* Xlibscm::
* Display::
* Screen::
* Window::
* Window Visibility::
* Graphics Context::
* Cursor::
* Colormap::
* Rendering::
* Event::
* Index::
@end menu

@node Xlibscm, Display, Top, Top
@chapter Xlibscm

@dfn{Xlibscm} is a SCM interface to @dfn{X}.
@cindex X
The
@ifset html
<A HREF="http://www.x.org/">
@end ifset
X Window System
@ifset html
</A>
@end ifset
is a network-transparent window system that was
designed at MIT.
@ifset html
<A HREF="scm_toc.html">
@end ifset
SCM
@ifset html
</A>
@end ifset
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 @code{(require
'Xlib)}.
@ftindex Xlib

@iftex
@noindent
The most recent information about SCM can be found on SCM's @dfn{WWW}
home page:
@center @url{http://swissnet.ai.mit.edu/~jaffer/SCM.html}
@end iftex

Much of this X documentation is dervied from:

@center Xlib - C Language X Interface
@center X Consortium Standard
@center 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.


@node Display, Screen, Xlibscm, Top
@chapter Display

@defun x:open-display display-name
@var{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
@var{DISPLAY} environment variable.

The encoding and interpretation of @var{display-name} is
implementation-dependent.  On POSIX-conformant systems, the
@var{display-name} or @var{DISPLAY} environment variable can be a string
in the format:

@defspec hostname:number.screen-number

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

@var{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.

@var{screen-number} specifies the screen to be used on that server.
Multiple screens can be controlled by a single X server.  The
@var{screen-number} sets an internal variable that can be accessed by
using the x:default-screen procedure.
@end defspec
@end defun

@defun x:close display
@var{display} specifies the connection to the X server.

The @code{x:close} function closes the connection to the X server for
the @var{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
@code{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 @var{x:close-display} or
@var{x:flush} explicitly so that any pending errors are reported.
@end defun

@defun x:protocol-version display
Returns cons of the major version number (11) of the X protocol
associated with the connected @var{display} and the minor protocol
revision number of the X server.
@end defun

@defun 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.
@end defun

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


@node Screen, Window, Display, Top
@chapter Screen

A display consists of one or more @dfn{Screen}s.  Each screen has a
@dfn{root-window}, @dfn{default-graphics-context}, @dfn{default-visual},
and @dfn{colormap}.

@defun x:screen-count display
Returns the number of available screens.
@end defun

@defun x:default-screen display
Returns the default screen number specified by the @code{x:open-display}
function.  Use this screen number in applications which will use only a
single screen.
@end defun

@defun x:root-window display screen-number
@defunx x:root-window display
@var{screen-number}, if givien, specifies the appropriate screen number
on the host server.  Otherwise the default-screen for @var{display} is
used.

Returns the root window for the specified @var{screen-number}.  Use
@code{x:root-window} for functions that need a drawable of a particular
screen or for creating top-level windows.

@defunx x:root-window window
Returns the root window for the specified @var{window}'s screen.
@end defun

@defun x:default-colormap display screen-number
@defunx x:default-colormap display
@defunx x:default-colormap window
Returns the default colormap of the specified screen.
@end defun

@defun x:default-gc display screen-number
@defunx x:default-gc display
@defunx x:default-gc window
Returns the default graphics-context of the specified screen.
@end defun

@defun x:default-depths display screen-number
@defunx x:default-depths display
@defunx x:default-depths window
Returns a vector of depths supported by the specified screen.
@end defun

The @dfn{Visual} type describes possible colormap depths and
arrangements.

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

@cindex visual
@cindex Visual
@end defun

@defun x:make-visual display depth class
@defunx x:make-visual window depth class

The integer @var{depth} specifies the number of bits per pixel.
The @var{class} argument specifies one of the possible
visual classes for a screen:
@itemize @bullet
@item x:Static-Gray
@item x:Static-Color
@item x:True-Color
@item x:Gray-Scale
@item x:Pseudo-Color
@item x:Direct-Color
@end itemize

@code{X:make-visual} returns a visual type for the screen specified by
@var{display} or @var{window} if successful; #f if not.

@end defun

@defun x:screen-cells display screen-number
@defunx x:screen-cells display
@defunx x:screen-cells window
Returns the number of entries in the default colormap.
@end defun

@defun x:screen-depth display screen-number
@defunx x:screen-depth display
@defunx x:screen-depth window
Returns the depth of the root window of the specified screen.

@cindex depth
The @dfn{depth} of a window or pixmap is the number of bits per pixel it has.
The @dfn{depth} of a graphics context is the depth of the drawables it can be
used in conjunction with graphics output.
@end defun

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

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

@defun x:screen-white display screen-number
@defunx x:screen-white display
@defunx x:screen-white window
Returns the white pixel value of the specified screen.
@end defun

@defun x:screen-black display screen-number
@defunx x:screen-black display
@defunx x:screen-black window
Returns the black pixel value of the specified screen.
@end defun


@node Window, Window Visibility, Screen, Top
@chapter Window

@cindex Drawable
@cindex drawable
A @dfn{Drawable} is either a window or pixmap.

@defun x:create-window window position size border-width depth class visual field-name value @dots{}
Creates and returns an unmapped Input-Output subwindow for a specified
parent @var{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 @var{window} is clipped.  The @var{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.

@var{Class} can be x:Input-Output, x:Input-Only, or x:Copy-From-Parent.
For class x:Input-Output, the @var{visual} type and @var{depth} must be
a combination supported for the screen.  The @var{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 @var{depth} must be zero,
and the @var{visual} must be one supported by the screen.

The returned window will have the attributes specified by
@var{field-name}s and @var{value}.

@defunx 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 @var{background} and
@var{border}, have their default values.
@end defun

@defun x:create-pixmap drawable size depth
@defunx x:create-pixmap display size depth

@var{size} is a list, vector, or pair of nonzero integers specifying the width
and height desired in the new pixmap.

@var{x:create-pixmap} returns a new pixmap of the width, height, and
@var{depth} specified.  It is valid to pass an x:Input-Only window to the
drawable argument.  The @var{depth} argument must be one of the depths
supported by the screen of the specified @var{drawable}.
@end defun

@defun x:close window
Destroys the specified @var{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
@var{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
@var{window} you specified is a root window, an error is signaled.
Destroying a mapped @var{window} will generate x:Expose events on other
windows that were obscured by the window being destroyed.
@end defun

@defun x:close pixmap
Deletes the association between the @var{pixmap} and its storage.  The X
server frees the pixmap storage when there are no references to it.
@end defun

@defun x:window-geometry drawable
Returns a list of:

@table @asis
@item coordinates
@code{cons} of x and y coordinates that define the location of the
@var{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.
@item size
@code{cons} of the @var{drawable}'s dimensions (width and height).  For
a window, these dimensions specify the inside size, not including the
border.
@item border-width
The border width in pixels.  If the @var{drawable} is a pixmap, this is
zero.
@item depth
The depth of the @var{drawable} (bits per pixel for the object).
@end table
@end defun

@defun x:window-set! window field-name value @dots{}
Changes the components specified by @var{field-name}s for the specified
@var{window}.  The restrictions are the same as for
@code{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.
@end defun

@heading Window Attributes

@noindent
The @code{x:create-window} and @code{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.

@defvr Attribute x:CW-Back-Pixmap
Sets the background pixmap of the @var{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.
@end defvr

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

@defvr Attribute x:CW-Border-Pixmap
Sets the border pixmap of the @var{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 @var{window}.
@end defvr

@defvr Attribute x:CW-Border-Pixel
Sets the border of the @var{window} to the pixel @var{value}.  It is an
error to perform this operation on an x:Input-Only window.
@end defvr

@defvr Attribute x:CW-Bit-Gravity
@defvrx 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:

@multitable @columnfractions .5 .5
@item Gravity Direction
@tab Coordinates
@item x:North-West-Gravity
@tab (0, 0)
@item x:North-Gravity
@tab (Width/2, 0)
@item x:North-East-Gravity
@tab (Width, 0)
@item x:West-Gravity
@tab (0, Height/2)
@item x:Center-Gravity
@tab (Width/2, Height/2)
@item x:East-Gravity
@tab (Width, Height/2)
@item x:South-West-Gravity
@tab (0, Height)
@item x:South-Gravity
@tab (Width/2, Height)
@item x:South-East-Gravity
@tab (Width, Height)
@end multitable

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.
@end defvr

@defvr 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.
@end defvr

@defvr Attribute x:CW-Backing-Planes
@defvrx 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.
@end defvr

@defvr 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.
@end defvr

@defvr 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.
@end defvr

@defvr 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:

@multitable @columnfractions .45 .55
@item Event Mask
@tab Circumstances
@item x:No-Event-Mask
@tab No events wanted
@item x:Key-Press-Mask
@tab Keyboard down events wanted
@item x:Key-Release-Mask
@tab Keyboard up events wanted
@item x:Button-Press-Mask
@tab Pointer button down events wanted
@item x:Button-Release-Mask
@tab Pointer button up events wanted
@item x:Enter-Window-Mask
@tab Pointer window entry events wanted
@item x:Leave-Window-Mask
@tab Pointer window leave events wanted
@item x:Pointer-Motion-Mask
@tab Pointer motion events wanted
@item x:Pointer-Motion-Hint-Mask
@tab
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.
@item x:Button1-Motion-Mask
@tab Pointer motion while button 1 down
@item x:Button2-Motion-Mask
@tab Pointer motion while button 2 down
@item x:Button3-Motion-Mask
@tab Pointer motion while button 3 down
@item x:Button4-Motion-Mask
@tab Pointer motion while button 4 down
@item x:Button5-Motion-Mask
@tab Pointer motion while button 5 down
@item x:Button-Motion-Mask
@tab Pointer motion while any button down
@item x:Keymap-State-Mask
@tab Keyboard state wanted at window entry and focus in
@item x:Exposure-Mask
@tab Any exposure wanted
@item x:Visibility-Change-Mask
@tab Any change in visibility wanted
@item x:Structure-Notify-Mask
@tab Any change in window structure wanted
@item x:Resize-Redirect-Mask
@tab Redirect resize of this window
@item x:Substructure-Notify-Mask
@tab Substructure notification wanted
@item x:Substructure-Redirect-Mask
@tab Redirect structure requests on children
@item x:Focus-Change-Mask
@tab Any change in input focus wanted
@item x:Property-Change-Mask
@tab Any change in property wanted
@item x:Colormap-Change--Mask
@tab Any change in colormap wanted
@item x:Owner-Grab-Button--Mask
@tab Automatic grabs should activate with owner_events set to True
@end multitable

@end defvr

@defvr 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).
@end defvr

@defvr 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.
@end defvr

@defvr 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.
@end defvr


@node Window Visibility, Graphics Context, Window, Top
@chapter Window Visibility

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

@defun x:map-window window
Maps the @var{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 @var{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 @code{x:map-window}
function does not map the @var{window}.  Otherwise, the @var{window} is
mapped, and the X server generates a MapNotify event.

If the @var{window} becomes viewable and no earlier contents for it are
remembered, the X server tiles the @var{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 @var{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, @code{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.
@end defun

@defun x:map-raised window
This procedure is similar to @code{x:map-window} in that it maps the
@var{window} and all of its subwindows that have had map requests.
However, it also raises the specified @var{window} to the top of the
stack.
@end defun

@defun x:map-subwindows window
Maps all subwindows of a specified @var{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.
@end defun

@defun x:unmap-window window
Unmaps the specified @var{window} and causes the X server to generate an
UnmapNotify event.  If the specified @var{window} is already unmapped,
@code{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 @var{window} will generate x:Expose events
on windows that were formerly obscured by it.
@end defun

@defun x:unmap-subwindows window
Unmaps all subwindows for the specified @var{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.
@end defun

@node Graphics Context, Cursor, Window Visibility, Top
@chapter Graphics Context

@noindent
Most attributes of graphics operations are stored in @dfn{GC}s.  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.

@defun x:create-gc drawable field-name value @dots{}
Creates and returns graphics context.  The graphics context can be used
with any destination drawable having the same root and depth as the
specified @var{drawable}.
@end defun

@defun x:gc-set! graphics-context field-name value @dots{}
Changes the components specified by @var{field-name}s for the specified
@var{graphics-context}.  The restrictions are the same as for
@code{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.
@end defun

@defun x:copy-gc-fields! gcontext-src gcontext-dst field-name @dots{}
Copies the components specified by @var{field-name}s from
@var{gcontext-src} to @var{gcontext-dst}.  @var{Gcontext-src} and
@var{gcontext-dst} must have the same root and depth.
@end defun

@defun x:gc-ref graphics-context field-name @dots{}
Returns a list of the components specified by @var{field-name}s @dots{}
from the specified @var{graphics-context}.
@end defun

@heading GC Attributes

@noindent
Both @code{x:create-gc} and @code{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.

@defvr 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:

@format
@t{
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}
@end format
@end defvr

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

@format
(OR (AND (FUNC src dst) plane-mask) (AND dst (NOT plane-mask)))
@end format

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

@defvr Attribute x:GC-Foreground
@defvrx 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.
@end defvr

@defvr 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.

@itemize @bullet
@item
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.

@item
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.
@end itemize

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.
@end defvr

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

@table @t
@item x:Line-Solid
The full path of the line is drawn.
@item 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.
@item 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.
@end table
@end defvr

@defvr Attribute x:GC-Cap-Style

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

@table @t
@item 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.
@item x:Cap-Butt
The line is square at the endpoint (perpendicular to the slope of the
line) with no projection beyond.
@item 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).
@item 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).
@end table
@end defvr

@defvr Attribute x:GC-Join-Style

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

@table @t
@item 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.
@item x:Join-Round
The corner is a circular arc with the diameter equal to the
line-width, centered on the x:Join-point.
@item x:Join-Bevel
The corner has x:Cap-Butt endpoint styles with the triangular notch filled.
@end table
@end defvr

@defvr 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:

@table @t
@item x:Fill-Solid
Foreground
@item x:Fill-Tiled
Tile
@item 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
@item x:Fill-Stippled
Foreground masked by stipple
@end table

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

@table @t
@item x:Fill-Solid
Background
@item x:Fill-Tiled
Same as for even dashes
@item x:Fill-Opaque-Stippled
Same as for even dashes
@item x:Fill-Stippled
Background masked by stipple
@end table
@end defvr

@defvr 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.

@table @t
@item 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.
@item 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.
@end table

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).
@end defvr

@defvr Attribute x:GC-Tile
@defvrx 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.
@end defvr

@defvr Attribute x:GC-Tile-Stip-X-Origin
@defvrx 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.
@end defvr

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

@defvr Attribute x:GC-Subwindow-Mode
You can set the subwindow-mode to x:Clip-By-Children or
x:Include-Inferiors.
@table @t
@item x:Clip-By-Children
Both source and destination windows are additionally clipped by all
viewable Input-Output children.
@item 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
@code{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.
@end table
@end defvr

@defvr 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).
@end defvr

@defvr Attribute x:GC-Clip-X-Origin
@defvrx 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.
@end defvr

@defvr 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
@cindex x:None
@cindex none
@dfn{x:None}, the pixels are always drawn regardless of the clip origin.
The clip-mask also can be set by calling @code{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.
@end defvr

@defvr 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.
@end defvr

@defvr Attribute x:GC-Dash-List
There must be at least one element in the specified @var{dash-list}.
The initial and alternating elements (second, fourth, and so on) of the
@var{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.
@end defvr

@defvr 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.
@table @t
@item x:Arc-Pie-Slice
The arcs are pie-slice filled.
@item x:Arc-Chord
The arcs are chord filled.
@end table
@end defvr


@node Cursor, Colormap, Graphics Context, Top
@chapter Cursor

@defun x:create-cursor display shape
X provides a set of standard cursor shapes in a special font named
@cindex cursor
@dfn{cursor}.  Applications are encouraged to use this interface for
their cursors because the font can be customized for the individual
display type.  The @var{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 @file{x11.scm}.

@defunx 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 @var{source-char} must be a defined
glyph in @var{source-font}.  The integer @var{mask-char} must be a
defined glyph in @var{mask-font}.  The origins of the @var{source-char}
and @var{mask-char} glyphs are positioned coincidently and define the
hotspot.  The @var{source-char} and @var{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.

@defunx x:create-cursor source-font source-char #f #f fgc bgc
If @var{mask-font} and @var{mask-char} are #f, all pixels of the source
are displayed.

@defunx x:create-cursor source-pixmap mask-pixmap fgc bgc origin
@var{mask-pixmap} must be the same size as the pixmap defined by the
@var{source-pixmap} argument.  The foreground and background RGB values
must be specified using @var{foreground-color} and
@var{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
@var{source-pixmap}.

@code{X:Create-Cursor} creates and returns a cursor.  The
@var{foreground-color} is used for the pixels set to 1 in the source,
and the @var{background-color} is used for the pixels set to 0.  Both
source and mask must have depth one but can have any root.  The
@var{mask-pixmap} defines the shape of the cursor.  The pixels set to 1
in @var{mask-pixmap} define which source pixels are displayed, and the
pixels set to 0 define which pixels are ignored.

@defunx x:create-cursor source-pixmap #f fgc bgc origin
If @var{mask-pixmap} is #f, all pixels of the source are displayed.
@end defun

@node Colormap, Rendering, Cursor, Top
@chapter Colormap

@cindex colormap
@cindex RGB
A @dfn{colormap} maps pixel values to @dfn{RGB} color space values.

@defun x:create-colormap window visual alloc-policy
@var{window} specifies the window on whose screen you want to create a
colormap.  @var{visual} specifies a visual type supported on the screen.
@var{alloc-policy} Specifies the colormap entries to be allocated.  You
can pass @code{X:Alloc-None} or @code{X:Alloc-All}.

The @code{X:Create-Colormap} function creates and returns a colormap of
the specified @var{visual} type for the screen on which @var{window}
resides.  Note that @var{window} is used only to determine the screen.

@table @samp
@item X:Gray-Scale
@itemx X:Pseudo-Color
@itemx X:Direct-Color
The initial values of the colormap entries are undefined.

@item X:Static-Gray
@itemx X:Static-Color
@itemx X:True-Color
The entries have defined values, but those values are specific to
@var{visual} and are not defined by X.  The @var{alloc-policy} must be
@samp{X:Alloc-None}.

@end table

For the other visual classes, if @var{alloc-policy} is
@samp{X:Alloc-None}, the colormap initially has no allocated entries,
and clients can allocate them.

If @var{alloc-policy} is @samp{X:Alloc-All}, the entire colormap is
allocated writable.  The initial values of all allocated entries are
undefined.

@table @samp
@item X:Gray-Scale
@itemx X:Pseudo-Color
The effect is as if an @code{XAllocColorCells} call returned all pixel
values from zero to N - 1, where N is the colormap entries value in
@var{visual}.

@item X:Direct-Color
The effect is as if an @code{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.
@end table

@end defun


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

@defun x:copy-colormap-and-free colormap

Creates and returns a colormap of the same visual type and for the same
screen as the specified @var{colormap}.  It also moves all of the
client's existing allocation from the specified @var{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 @samp{X:Alloc-All}, the new colormap is also created with
@samp{X:Alloc-All}, all color values for all entries are copied from the
specified @var{colormap}, and then all entries in the specified
@var{colormap} are freed.  If the specified @var{colormap} was not
created by the client with @samp{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.

@end defun

A @dfn{colormap} maps pixel values to elements of the @dfn{RGB}
datatype.  An @var{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.

@defun x:alloc-colormap-cells colormap ncolors nplanes
@defunx x:alloc-colormap-cells colormap ncolors nplanes contiguous?

The @code{X:Alloc-Color-Cells} function allocates read/write color
cells.  The number of colors, @var{ncolors} must be positive and the
number of planes, @var{nplanes} nonnegative.  If @var{ncolors} and
nplanes are requested, then @var{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, @var{ncolors} * 2^@var{nplanes} distinct pixels can
be produced.  All of these are allocated writable by the request.

@table @samp
@item x:Gray-Scale
@itemx x:Pseudo-Color
Each mask has exactly one bit set to 1.  If @var{contiguous?} is
non-false and if all masks are ORed together, a single contiguous set of
bits set to 1 is formed.
@item x:Direct-Color
Each mask has exactly three bits set to 1.  If @var{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.
@end table

The RGB values of the allocated entries are undefined.
@code{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.


@defunx x:alloc-colormap-cells colormap ncolors rgb
@defunx x:alloc-colormap-cells colormap ncolors rgb contiguous?

The specified @var{ncolors} must be positive; and @var{rgb} a list or
vector of 3 nonnegative integers.  If @var{ncolors} colors, @var{nreds}
reds, @var{ngreens} greens, and @var{nblues} blues are requested,
@var{ncolors} pixels are returned; and the masks have @var{nreds},
@var{ngreens}, and @var{nblues} bits set to 1, respectively.  If
@var{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, @var{ncolors} *
2(@var{nreds}+@var{ngreens}+@var{nblues}) distinct pixel values can be
produced.  All of these are allocated by the request.  However, in the
colormap, there are only @var{ncolors} * 2^@var{nreds} independent red
entries, @var{ncolors} * 2^@var{ngreens} independent green entries, and
@var{ncolors} * 2^@var{nblues} independent blue entries.

@code{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.
@end defun

@defun x:free-colormap-cells colormap pixels planes
@defunx x:free-colormap-cells colormap pixels

Frees the cells represented by pixels whose values are in the
@var{pixels} unsigned-integer uniform-vector.  The @var{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
@var{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 @code{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
@var{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
@samp{x:Alloc-All} to @code{X:Create-Colormap}).  If more than one pixel
is in error, the one that gets reported is arbitrary.
@end defun

@defun x:colormap-find-color colormap rgb

@var{rgb} is a list or vector of 3 integers, describing the red, green,
and blue intensities respectively; or an integer @samp{#x@i{rrggbb}},
packing red, green and blue intensities in the range 0 - 255.

@defunx x:colormap-find-color colormap color-name

The case-insensitive string @var{color_name} specifies the name of a
color (for example, @file{red})

@code{X:Colormap-Find-Color} allocates a read-only colormap entry
corresponding to the closest RGB value supported by the hardware.
@code{X:Colormap-Find-Color} returns the pixel value of the color
closest to the specified @var{RGB} or @var{color_name} elements
supported by the hardware, if successful; otherwise
@code{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.

@end defun

@defun x:color-ref colormap pixel

Returns a list of 3 integers, describing the red, green,
and blue intensities respectively of the @var{colormap} entry of the
cell indexed by @var{pixel}.

The integer @var{pixel} must be a valid index into @var{colormap}.
@end defun

@defun X:Color-Set! colormap pixel rgb

@var{rgb} is a list or vector of 3 integers, describing the red, green,
and blue intensities respectively; or an integer @samp{#x@i{rrggbb}},
packing red, green and blue intensities in the range 0 - 255.

@defunx X:Color-Set! colormap pixel color-name

The case-insensitive string @var{color_name} specifies the name of a
color (for example, @file{red})

The integer @var{pixel} must be a valid index into @var{colormap}.

@code{X:Color-Set!} changes the @var{colormap} entry of the read/write
cell indexed by @var{pixel}.  If the @var{colormap} is an installed map
for its screen, the changes are visible immediately.

@end defun

@defun x:install-colormap colormap

Installs the specified @var{colormap} for its associated screen.  All
windows associated with @var{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.

@end defun


@node Rendering, Event, Colormap, Top
@chapter Rendering

@defun x:flush display
@defunx 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.

@defunx 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.
@end defun

@defun x:clear-area window (x-pos y-pos) (width height) expose?
Paints a rectangular area in the specified @var{window} according to the
specified dimensions with the @var{window}'s background pixel or pixmap.
The subwindow-mode effectively is @samp{x:Clip-By-Children}.  If width
is zero, it is replaced with the current width of the @var{window} minus
x.  If height is zero, it is replaced with the current height of the
@var{window} minus y.  If the @var{window} has a defined background
tile, the rectangle clipped by any children is filled with this tile.
If the @var{window} has background x:None, the contents of the
@var{window} are not changed.  In either case, if @var{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 @var{window} whose class is x:Input-Only, an error
results.
@end defun

@defun x:fill-rectangle window gcontext position size

@end defun

@heading Draw Strings

@defun x:draw-string drawable gc position string
@var{Position} specifies coordinates relative to the origin of
@var{drawable} of the origin of the first character to be drawn.

@code{x:draw-string} draws the characters of @var{string}, starting at
@var{position}.
@end defun

@defun x:image-string drawable gc position string
@var{Position} specifies coordinates relative to the origin of
@var{drawable} of the origin of the first character to be drawn.

@code{x:image-string} draws the characters @emph{and background} of
@var{string}, starting at @var{position}.
@end defun

@heading Draw Shapes

@defun x:draw-points drawable gc position @dots{}
@var{Position} @dots{} specifies coordinates of the point to be drawn.

@defunx x:draw-points drawable gc x y @dots{}
(@var{x}, @var{y}) @dots{} specifies coordinates of the point to be
drawn.

@defunx x:draw-points drawable gc point-array
@var{point-array} is a uniform short array of rank 2, whose rightmost
index spans a range of 2.

The @code{X:Draw-Points} procedure uses the foreground pixel and
function components of the @var{gc} to draw points into @var{drawable}
at the positions (relative to the origin of @var{drawable}) specified.

@code{X:Draw-Points} uses these @var{gc} components: function,
planemask, foreground, subwindow-mode, clip-x-origin, clip-y-origin, and
clip-mask.
@end defun


@defun x:draw-segments drawable gc pos1 pos2 @dots{}
@var{Pos1}, @var{pos2}, @dots{} specify coordinates to be connected by
segments.

@defunx x:draw-segments drawable gc x1 y1 x2 y2 @dots{}
(@var{x1}, @var{y1}), (@var{x2}, @var{y2}) @dots{} specify coordinates
to be connected by segments.

@defunx x:draw-segments drawable gc point-array
@var{point-array} is a uniform short array of rank 2, whose rightmost
index spans a range of 2.

The @code{X:Draw-Segments} procedure uses the components of the
specified @var{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, @code{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.  @code{X:Draw-Segments} treats all
coordinates as relative to the origin of @var{drawable}.

@code{X:Draw-Segments} uses these @var{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 @var{gc} mode-dependent components: foreground,
background, tile, stipple, tilestipple-x-origin, tile-stipple-y-origin,
dash-offset, and dash-list.
@end defun

@defun x:draw-lines drawable gc pos1 pos2 @dots{}
@var{Pos1}, @var{pos2}, @dots{} specify coordinates to be connected by
lines.

@defunx x:draw-lines drawable gc x1 y1 x2 y2 @dots{}
(@var{x1}, @var{y1}), (@var{x2}, @var{y2}) @dots{} specify coordinates
to be connected by lines.

@defunx x:draw-lines drawable gc point-array
@var{point-array} is a uniform short array of rank 2, whose rightmost
index spans a range of 2.

The @code{X:Draw-Lines} procedure uses the components of the specified
@var{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,
@code{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.  @code{X:Draw-Lines} treats all coordinates as relative to
the origin of @var{drawable}.

@code{X:Draw-Lines} uses these @var{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 @var{gc} mode-dependent components: foreground,
background, tile, stipple, tilestipple-x-origin, tile-stipple-y-origin,
dash-offset, and dash-list.
@end defun

@defun x:fill-polygon drawable gc pos1 pos2 @dots{}
@var{Pos1}, @var{pos2}, @dots{} specify coordinates of the border path.

@defunx x:fill-polygon drawable gc x1 y1 x2 y2 @dots{}
(@var{x1}, @var{y1}), (@var{x2}, @var{y2}) @dots{} specify coordinates
of the border path.

@defunx x:fill-polygon drawable gc point-array
@var{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
@var{point-array} does not coincide with the first point.

The @code{X:Fill-Polygon} procedure uses the components of the specified
@var{gc} to fill the region closed by the specified path.
@code{X:Fill-Polygon} does not draw a pixel of the region more than
once.  @code{X:Fill-Polygon} treats all coordinates as relative to the
origin of @var{drawable}.

@code{X:Fill-Polygon} uses these @var{gc} components: function,
planemask, fill-style, fill-rule, subwindow-mode, clip-x-origin,
clip-y-origin, and clip-mask.  It also use these @var{gc} mode-dependent
components: foreground, background, tile, stipple,
tile-stipple-x-origin, and tile-stipple-y-origin.
@end defun

@node Event, Index, Rendering, Top
@chapter Event

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

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

@defun 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.
@end defun

@defun 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, @code{X:Events-Queued}
attempts to read more events out of the application's connection without
flushing the output buffer and returns the number read.
@end defun

@noindent
Both of these routines return an object of type @dfn{event}.

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

@defun 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, @code{X:Peek-Event}
flushes the output buffer and blocks until an event is received.
@end defun

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

@defun x:event-ref event field-name
@multitable @columnfractions .40 .60
@item window
@tab
The window on which @var{event} was generated and is referred to as the
event window.
@item root
@tab
is the event window's root window.
@item subwindow
@tab
If the source window is an inferior of the event window, the
@var{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, @samp{None}.
@item X-event:type
@tab
An integer: @var{x:Key-Press}, @var{x:Key-Release},
@var{x:Button-Press}, @var{x:Button-Release}, @var{x:Motion-Notify},
@var{x:Enter-Notify}, @var{x:Leave-Notify}, @var{x:Focus-In},
@var{x:Focus-Out}, @var{x:Keymap-Notify}, @var{x:Expose},
@var{x:Graphics-Expose}, @var{x:No-Expose}, @var{x:Visibility-Notify},
@var{x:Create-Notify}, @var{x:Destroy-Notify}, @var{x:Unmap-Notify},
@var{x:Map-Notify}, @var{x:Map-Request}, @var{x:Reparent-Notify},
@var{x:Configure-Notify}, @var{x:Configure-Request},
@var{x:Gravity-Notify}, @var{x:Resize-Request},
@var{x:Circulate-Notify}, @var{x:Circulate-Request},
@var{x:Property-Notify}, @var{x:Selection-Clear},
@var{x:Selection-Request}, @var{x:Selection-Notify},
@var{x:Colormap-Notify}, @var{x:Client-Message}, or
@var{x:Mapping-Notify}.
@item X-event:serial
@tab
The serial number of the protocol request that generated the @var{event}.
@item X-event:send-event
@tab
Boolean that indicates whether the event was sent by a different client.
@item X-event:time
@tab
The time when the @var{event} was generated expressed in milliseconds.
@item X-event:x
@item X-event:y
@tab
For window entry/exit events the @var{x} and @var{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,
@var{x} and @var{y} are the pointer coordinates relative to the event
window's origin.  Otherwise, @var{x} and @var{y} are set to zero.

For expose events The @var{x} and @var{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 @var{x} and
@var{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.
@item X-event:x-root
@itemx X-event:y-root
@tab
The pointer's coordinates relative to the root window's origin at the
time of the @var{event}.
@item X-event:state
@tab
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 @var{event}, which is the bitwise inclusive OR of
one or more of the button or modifier key masks: @var{x:Button1-Mask},
@var{x:Button2-Mask}, @var{x:Button3-Mask}, @var{x:Button4-Mask},
@var{x:Button5-Mask}, @var{x:Shift-Mask}, @var{x:Lock-Mask},
@var{x:Control-Mask}, @var{x:Mod1-Mask}, @var{x:Mod2-Mask},
@var{x:Mod3-Mask}, @var{x:Mod4-Mask}, and @var{x:Mod5-Mask}.

For visibility events, the state of the window's visibility:
@var{x:Visibility-Unobscured}, @var{x:Visibility-Partially-Obscured}, or
@var{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.
@item X-event:keycode
@tab
An integer that represents a physical key on the keyboard.
@item X-event:same-screen
@tab
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.
@item X-event:button
@tab
The pointer button that changed state; can be the @var{x:Button1},
@var{x:Button2}, @var{x:Button3}, @var{x:Button4}, or @var{x:Button5}
value.
@item X-event:is-hint
@tab
Detail of motion-notify events: @var{x:Notify-Normal} or
@var{x:Notify-Hint}.
@item X-event:mode
@tab
Indicates whether the @var{event} is a normal event, pseudo-motion event
when a grab activates, or a pseudo-motion event when a grab deactivates:
@var{x:Notify-Normal}, @var{x:Notify-Grab}, or @var{x:Notify-Ungrab}.
@item X-event:detail
@tab
Indicates the notification detail: @var{x:Notify-Ancestor},
@var{x:Notify-Virtual}, @var{x:Notify-Inferior},
@var{x:Notify-Nonlinear}, or @var{x:Notify-Nonlinear-Virtual}.
@item X-event:focus
@tab
If the event window is the focus window or an inferior of the focus
window, #t; otherwise #f.
@item X-event:width
@itemx X-event:height
@tab
The size (extent) of the rectangle.
@item X-event:count
@tab
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.
@item X-event:major-code
@tab
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.
@item X-event:minor-code
@tab
Not currently used.
@item X-event:border-width
@tab
For configure events, the width of the window's border, in pixels.
@item X-event:override-redirect
@tab
The override-redirect attribute of the window.  Window manager clients
normally should ignore this window if it is #t.
@item X-event:from-configure
@tab
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.
@item X-event:value-mask
@tab
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.
@item X-event:place
@tab
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.
@item X-event:new
@tab
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.
@item X-event:format
@tab
Is 8, 16, or 32 and specifies whether the data should be viewed as a
list of bytes, shorts, or longs
@item X-event:request
@tab
Indicates the kind of mapping change that occurred and can be
@var{x:Mapping-Modifier}, @var{x:Mapping-Keyboard}, or
@var{x:Mapping-Pointer}.  If it is @var{x:Mapping-Modifier}, the
modifier mapping was changed.  If it is @var{x:Mapping-Keyboard}, the
keyboard mapping was changed.  If it is @var{x:Mapping-Pointer}, the
pointer button mapping was changed.
@item X-event:first-keycode
@tab
The X-event:first-keycode is set only if the X-event:request was set to
@var{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.
@end multitable
@end defun

@node Index,  , Event, Top
@c @node Procedure and Macro Index, Variable Index, The Implementation, Top
@unnumbered Procedure and Macro Index

This is an alphabetical list of all the procedures and macros in Xlibscm.

@printindex fn

@c @node Variable Index, Type Index, Procedure and Macro Index, Top
@unnumbered Variable Index

This is an alphabetical list of all the global variables in Xlibscm.

@printindex vr

This is an alphabetical list of concepts introduced in this manual.

@unnumbered Concept Index
@printindex cp

@contents
@bye