Revert "update upstream sources"

[clinton/guile-figl.git] / doc / low-level-glx.texi

@c %start of fragment

The functions from this section may be had by loading the module:

@example 
(use-modules (figl glx low-level)
@end example

@copying 
This section of the manual was derived from the upstream OpenGL
documentation. Each function's documentation has its own copyright
statement; for full details, see the upstream documentation. The
copyright notices and licenses present in this section are as follows.

Copyright @copyright{} 1991-2006 Silicon Graphics, Inc. This document is
licensed under the SGI Free Software B License. For details, see
@uref{http://oss.sgi.com/projects/FreeB/,http://oss.sgi.com/projects/FreeB/}.

@end copying

@deftypefun GLXFBConfig-* glXChooseFBConfig dpy screen attrib_list nelements
Return a list of GLX frame buffer configurations that match the
specified attributes.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{screen}
Specifies the screen number.

@item @var{attrib_list}
Specifies a list of attribute/value pairs. The last attribute must be
@code{None}.

@item @var{nelements}
Returns the number of elements in the list returned by
@code{glXChooseFBConfig}.

@end table

@code{glXChooseFBConfig} returns GLX frame buffer configurations that
match the attributes specified in @var{attrib_list}, or @code{NULL} if
no matches are found. If @var{attrib_list} is @code{NULL}, then
@code{glXChooseFBConfig} returns an array of GLX frame buffer
configurations that are available on the specified screen. If an error
occurs, no frame buffer configurations exist on the specified screen, or
if no frame buffer configurations match the specified attributes, then
@code{NULL} is returned. Use @code{XFree} to free the memory returned by
@code{glXChooseFBConfig}.

All attributes in @var{attrib_list}, including boolean attributes, are
immediately followed by the corresponding desired value. The list is
terminated with @code{None}. If an attribute is not specified in
@var{attrib_list}, then the default value (see below) is used (and the
attribute is said to be specified implicitly). For example, if
@code{GLX_STEREO} is not specified, then it is assumed to be
@code{False}. For some attributes, the default is @code{GLX_DONT_CARE},
meaning that any value is OK for this attribute, so the attribute will
not be checked.

Attributes are matched in an attribute-specific manner. Some of the
attributes, such as @code{GLX_LEVEL}, must match the specified value
exactly; others, such as, @code{GLX_RED_SIZE} must meet or exceed the
specified minimum values. If more than one GLX frame buffer
configuration is found, then a list of configurations, sorted according
to the ``best'' match criteria, is returned. The match criteria for each
attribute and the exact sorting order is defined below.

The interpretations of the various GLX visual attributes are as follows:

@table @asis
@item @code{GLX_FBCONFIG_ID}


Must be followed by a valid XID that indicates the desired GLX frame
buffer configuration. When a @code{GLX_FBCONFIG_ID} is specified, all
attributes are ignored. The default value is @code{GLX_DONT_CARE}.

@item @code{GLX_BUFFER_SIZE}


Must be followed by a nonnegative integer that indicates the desired
color index buffer size. The smallest index buffer of at least the
specified size is preferred. This attribute is ignored if
@code{GLX_COLOR_INDEX_BIT} is not set in @code{GLX_RENDER_TYPE}. The
default value is 0.

@item @code{GLX_LEVEL}


Must be followed by an integer buffer-level specification. This
specification is honored exactly. Buffer level 0 corresponds to the
default frame buffer of the display. Buffer level 1 is the first overlay
frame buffer, level two the second overlay frame buffer, and so on.
Negative buffer levels correspond to underlay frame buffers. The default
value is 0.

@item @code{GLX_DOUBLEBUFFER}


Must be followed by @code{True} or @code{False}. If @code{True} is
specified, then only double-buffered frame buffer configurations are
considered; if @code{False} is specified, then only single-buffered
frame buffer configurations are considered. The default value is
@code{GLX_DONT_CARE}.

@item @code{GLX_STEREO}


Must be followed by @code{True} or @code{False}. If @code{True} is
specified, then only stereo frame buffer configurations are considered;
if @code{False} is specified, then only monoscopic frame buffer
configurations are considered. The default value is @code{False}.

@item @code{GLX_AUX_BUFFERS}


Must be followed by a nonnegative integer that indicates the desired
number of auxiliary buffers. Configurations with the smallest number of
auxiliary buffers that meet or exceed the specified number are
preferred. The default value is 0.

@item @code{GLX_RED_SIZE}, @code{GLX_GREEN_SIZE}, @code{GLX_BLUE_SIZE}, @code{GLX_ALPHA_SIZE}


Each attribute, if present, must be followed by a nonnegative minimum
size specification or @code{GLX_DONT_CARE}. The largest available total
RGBA color buffer size (sum of @code{GLX_RED_SIZE},
@code{GLX_GREEN_SIZE}, @code{GLX_BLUE_SIZE}, and @code{GLX_ALPHA_SIZE})
of at least the minimum size specified for each color component is
preferred. If the requested number of bits for a color component is 0 or
@code{GLX_DONT_CARE}, it is not considered. The default value for each
color component is 0.

@item @code{GLX_DEPTH_SIZE}


Must be followed by a nonnegative minimum size specification. If this
value is zero, frame buffer configurations with no depth buffer are
preferred. Otherwise, the largest available depth buffer of at least the
minimum size is preferred. The default value is 0.

@item @code{GLX_STENCIL_SIZE}


Must be followed by a nonnegative integer that indicates the desired
number of stencil bitplanes. The smallest stencil buffer of at least the
specified size is preferred. If the desired value is zero, frame buffer
configurations with no stencil buffer are preferred. The default value
is 0.

@item @code{GLX_ACCUM_RED_SIZE}


Must be followed by a nonnegative minimum size specification. If this
value is zero, frame buffer configurations with no red accumulation
buffer are preferred. Otherwise, the largest possible red accumulation
buffer of at least the minimum size is preferred. The default value is
0.

@item @code{GLX_ACCUM_GREEN_SIZE}


Must be followed by a nonnegative minimum size specification. If this
value is zero, frame buffer configurations with no green accumulation
buffer are preferred. Otherwise, the largest possible green accumulation
buffer of at least the minimum size is preferred. The default value is
0.

@item @code{GLX_ACCUM_BLUE_SIZE}


Must be followed by a nonnegative minimum size specification. If this
value is zero, frame buffer configurations with no blue accumulation
buffer are preferred. Otherwise, the largest possible blue accumulation
buffer of at least the minimum size is preferred. The default value is
0.

@item @code{GLX_ACCUM_ALPHA_SIZE}


Must be followed by a nonnegative minimum size specification. If this
value is zero, frame buffer configurations with no alpha accumulation
buffer are preferred. Otherwise, the largest possible alpha accumulation
buffer of at least the minimum size is preferred. The default value is
0.

@item @code{GLX_RENDER_TYPE}


Must be followed by a mask indicating which OpenGL rendering modes the
frame buffer configuration must support. Valid bits are
@code{GLX_RGBA_BIT} and @code{GLX_COLOR_INDEX_BIT}. If the mask is set
to @code{GLX_RGBA_BIT} | @code{GLX_COLOR_INDEX_BIT}, then only frame
buffer configurations that can be bound to both RGBA contexts and color
index contexts will be considered. The default value is
@code{GLX_RGBA_BIT}.

@item @code{GLX_DRAWABLE_TYPE}


Must be followed by a mask indicating which GLX drawable types the frame
buffer configuration must support. Valid bits are @code{GLX_WINDOW_BIT},
@code{GLX_PIXMAP_BIT}, and @code{GLX_PBUFFER_BIT}. For example, if mask
is set to @code{GLX_WINDOW_BIT} | @code{GLX_PIXMAP_BIT}, only frame
buffer configurations that support both windows and GLX pixmaps will be
considered. The default value is @code{GLX_WINDOW_BIT}.

@item @code{GLX_X_RENDERABLE}


Must be followed by @code{True} or @code{False}. If @code{True} is
specified, then only frame buffer configurations that have associated X
visuals (and can be used to render to Windows and/or GLX pixmaps) will
be considered. The default value is @code{GLX_DONT_CARE}.

@item @code{GLX_X_VISUAL_TYPE}


Must be followed by one of @code{GLX_TRUE_COLOR},
@code{GLX_DIRECT_COLOR}, @code{GLX_PSEUDO_COLOR},
@code{GLX_STATIC_COLOR}, @code{GLX_GRAY_SCALE}, or
@code{GLX_STATIC_GRAY}, indicating the desired X visual type. Not all
frame buffer configurations have an associated X visual. If
@code{GLX_DRAWABLE_TYPE} is specified in @var{attrib_list} and the mask
that follows does not have @code{GLX_WINDOW_BIT} set, then this value is
ignored. It is also ignored if @code{GLX_X_RENDERABLE} is specified as
@code{False}. RGBA rendering may be supported for visuals of type
@code{GLX_TRUE_COLOR}, @code{GLX_DIRECT_COLOR}, @code{GLX_PSEUDO_COLOR},
or @code{GLX_STATIC_COLOR}, but color index rendering is only supported
for visuals of type @code{GLX_PSEUDO_COLOR} or @code{GLX_STATIC_COLOR}
(i.e., single-channel visuals). The tokens @code{GLX_GRAY_SCALE} and
@code{GLX_STATIC_GRAY} will not match current OpenGL enabled visuals,
but are included for future use. The default value for
@code{GLX_X_VISUAL_TYPE} is @code{GLX_DONT_CARE}.

@item @code{GLX_CONFIG_CAVEAT}


Must be followed by one of @code{GLX_NONE}, @code{GLX_SLOW_CONFIG},
@code{GLX_NON_CONFORMANT_CONFIG}. If @code{GLX_NONE} is specified, then
only frame buffer configurations with no caveats will be considered; if
@code{GLX_SLOW_CONFIG} is specified, then only slow frame buffer
configurations will be considered; if @code{GLX_NON_CONFORMANT_CONFIG}
is specified, then only nonconformant frame buffer configurations will
be considered. The default value is @code{GLX_DONT_CARE}.

@item @code{GLX_TRANSPARENT_TYPE}


Must be followed by one of @code{GLX_NONE}, @code{GLX_TRANSPARENT_RGB},
@code{GLX_TRANSPARENT_INDEX}. If @code{GLX_NONE} is specified, then only
opaque frame buffer configurations will be considered; if
@code{GLX_TRANSPARENT_RGB} is specified, then only transparent frame
buffer configurations that support RGBA rendering will be considered; if
@code{GLX_TRANSPARENT_INDEX} is specified, then only transparent frame
buffer configurations that support color index rendering will be
considered. The default value is @code{GLX_NONE}.

@item @code{GLX_TRANSPARENT_INDEX_VALUE}


Must be followed by an integer value indicating the transparent index
value; the value must be between 0 and the maximum frame buffer value
for indices. Only frame buffer configurations that use the specified
transparent index value will be considered. The default value is
@code{GLX_DONT_CARE}. This attribute is ignored unless
@code{GLX_TRANSPARENT_TYPE} is included in @var{attrib_list} and
specified as @code{GLX_TRANSPARENT_INDEX}.

@item @code{GLX_TRANSPARENT_RED_VALUE}


Must be followed by an integer value indicating the transparent red
value; the value must be between 0 and the maximum frame buffer value
for red. Only frame buffer configurations that use the specified
transparent red value will be considered. The default value is
@code{GLX_DONT_CARE}. This attribute is ignored unless
@code{GLX_TRANSPARENT_TYPE} is included in @var{attrib_list} and
specified as @code{GLX_TRANSPARENT_RGB}.

@item @code{GLX_TRANSPARENT_GREEN_VALUE}


Must be followed by an integer value indicating the transparent green
value; the value must be between 0 and the maximum frame buffer value
for green. Only frame buffer configurations that use the specified
transparent green value will be considered. The default value is
@code{GLX_DONT_CARE}. This attribute is ignored unless
@code{GLX_TRANSPARENT_TYPE} is included in @var{attrib_list} and
specified as @code{GLX_TRANSPARENT_RGB}.

@item @code{GLX_TRANSPARENT_BLUE_VALUE}


Must be followed by an integer value indicating the transparent blue
value; the value must be between 0 and the maximum frame buffer value
for blue. Only frame buffer configurations that use the specified
transparent blue value will be considered. The default value is
@code{GLX_DONT_CARE}. This attribute is ignored unless
@code{GLX_TRANSPARENT_TYPE} is included in @var{attrib_list} and
specified as @code{GLX_TRANSPARENT_RGB}.

@item @code{GLX_TRANSPARENT_ALPHA_VALUE}


Must be followed by an integer value indicating the transparent alpha
value; the value must be between 0 and the maximum frame buffer value
for alpha. Only frame buffer configurations that use the specified
transparent alpha value will be considered. The default value is
@code{GLX_DONT_CARE}.

@end table

When more than one GLX frame buffer configuration matches the specified
attributes, a list of matching configurations is returned. The list is
sorted according to the following precedence rules, which are applied in
ascending order (i.e., configurations that are considered equal by a
lower numbered rule are sorted by the higher numbered rule):

@table @asis
@item 1.
By @code{GLX_CONFIG_CAVEAT} where the precedence is @code{GLX_NONE},
@code{GLX_SLOW_CONFIG}, and @code{GLX_NON_CONFORMANT_CONFIG}.

@item 2.
Larger total number of RGBA color components (@code{GLX_RED_SIZE},
@code{GLX_GREEN_SIZE}, @code{GLX_BLUE_SIZE}, plus @code{GLX_ALPHA_SIZE})
that have higher number of bits. If the requested number of bits in
@var{attrib_list} is zero or @code{GLX_DONT_CARE} for a particular color
component, then the number of bits for that component is not considered.

@item 3.
Smaller @code{GLX_BUFFER_SIZE}.

@item 4.
Single buffered configuration (@code{GLX_DOUBLEBUFFER} being
@code{False} precedes a double buffered one.

@item 5.
Smaller @code{GLX_AUX_BUFFERS}.

@item 6.
Larger @code{GLX_DEPTH_SIZE}.

@item 7.
Smaller @code{GLX_STENCIL_SIZE}.

@item 8.
Larger total number of accumulation buffer color components
(@code{GLX_ACCUM_RED_SIZE}, @code{GLX_ACCUM_GREEN_SIZE},
@code{GLX_ACCUM_BLUE_SIZE}, plus @code{GLX_ACCUM_ALPHA_SIZE}) that have
higher number of bits. If the requested number of bits in
@var{attrib_list} is zero or @code{GLX_DONT_CARE} for a particular color
component, then the number of bits for that component is not considered.

@item 9.
By @code{GLX_X_VISUAL_TYPE} where the precedence order is
@code{GLX_TRUE_COLOR}, @code{GLX_DIRECT_COLOR}, @code{GLX_PSEUDO_COLOR},
@code{GLX_STATIC_COLOR}, @code{GLX_GRAY_SCALE}, @code{GLX_STATIC_GRAY}.

@end table

@code{NULL} is returned if an undefined GLX attribute is encountered in
@var{attrib_list}, if @var{screen} is invalid, or if @var{dpy} does not
support the GLX extension.

@end deftypefun

@deftypefun XVisualInfo* glXChooseVisual dpy screen attribList
Return a visual that matches specified attributes.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{screen}
Specifies the screen number.

@item @var{attribList}
Specifies a list of boolean attributes and integer attribute/value
pairs. The last attribute must be @code{None}.

@end table

@code{glXChooseVisual} returns a pointer to an XVisualInfo structure
describing the visual that best meets a minimum specification. The
boolean GLX attributes of the visual that is returned will match the
specified values, and the integer GLX attributes will meet or exceed the
specified minimum values. If all other attributes are equivalent, then
TrueColor and PseudoColor visuals have priority over DirectColor and
StaticColor visuals, respectively. If no conforming visual exists,
@code{NULL} is returned. To free the data returned by this function, use
@code{XFree}.

All boolean GLX attributes default to @code{False} except
@code{GLX_USE_GL}, which defaults to @code{True}. All integer GLX
attributes default to zero. Default specifications are superseded by
attributes included in @var{attribList}. Boolean attributes included in
@var{attribList} are understood to be @code{True}. Integer attributes
and enumerated type attributes are followed immediately by the
corresponding desired or minimum value. The list must be terminated with
@code{None}.

The interpretations of the various GLX visual attributes are as follows:

@table @asis
@item @code{GLX_USE_GL}
Ignored. Only visuals that can be rendered with GLX are considered.

@item @code{GLX_BUFFER_SIZE}
Must be followed by a nonnegative integer that indicates the desired
color index buffer size. The smallest index buffer of at least the
specified size is preferred. Ignored if @code{GLX_RGBA} is asserted.

@item @code{GLX_LEVEL}
Must be followed by an integer buffer-level specification. This
specification is honored exactly. Buffer level zero corresponds to the
main frame buffer of the display. Buffer level one is the first overlay
frame buffer, level two the second overlay frame buffer, and so on.
Negative buffer levels correspond to underlay frame buffers.

@item @code{GLX_RGBA}
If present, only TrueColor and DirectColor visuals are considered.
Otherwise, only PseudoColor and StaticColor visuals are considered.

@item @code{GLX_DOUBLEBUFFER}
If present, only double-buffered visuals are considered. Otherwise, only
single-buffered visuals are considered.

@item @code{GLX_STEREO}
If present, only stereo visuals are considered. Otherwise, only
monoscopic visuals are considered.

@item @code{GLX_AUX_BUFFERS}
Must be followed by a nonnegative integer that indicates the desired
number of auxiliary buffers. Visuals with the smallest number of
auxiliary buffers that meets or exceeds the specified number are
preferred.

@item @code{GLX_RED_SIZE}
Must be followed by a nonnegative minimum size specification. If this
value is zero, the smallest available red buffer is preferred.
Otherwise, the largest available red buffer of at least the minimum size
is preferred.

@item @code{GLX_GREEN_SIZE}
Must be followed by a nonnegative minimum size specification. If this
value is zero, the smallest available green buffer is preferred.
Otherwise, the largest available green buffer of at least the minimum
size is preferred.

@item @code{GLX_BLUE_SIZE}
Must be followed by a nonnegative minimum size specification. If this
value is zero, the smallest available blue buffer is preferred.
Otherwise, the largest available blue buffer of at least the minimum
size is preferred.

@item @code{GLX_ALPHA_SIZE}
Must be followed by a nonnegative minimum size specification. If this
value is zero, the smallest available alpha buffer is preferred.
Otherwise, the largest available alpha buffer of at least the minimum
size is preferred.

@item @code{GLX_DEPTH_SIZE}
Must be followed by a nonnegative minimum size specification. If this
value is zero, visuals with no depth buffer are preferred. Otherwise,
the largest available depth buffer of at least the minimum size is
preferred.

@item @code{GLX_STENCIL_SIZE}
Must be followed by a nonnegative integer that indicates the desired
number of stencil bitplanes. The smallest stencil buffer of at least the
specified size is preferred. If the desired value is zero, visuals with
no stencil buffer are preferred.

@item @code{GLX_ACCUM_RED_SIZE}
Must be followed by a nonnegative minimum size specification. If this
value is zero, visuals with no red accumulation buffer are preferred.
Otherwise, the largest possible red accumulation buffer of at least the
minimum size is preferred.

@item @code{GLX_ACCUM_GREEN_SIZE}
Must be followed by a nonnegative minimum size specification. If this
value is zero, visuals with no green accumulation buffer are preferred.
Otherwise, the largest possible green accumulation buffer of at least
the minimum size is preferred.

@item @code{GLX_ACCUM_BLUE_SIZE}
Must be followed by a nonnegative minimum size specification. If this
value is zero, visuals with no blue accumulation buffer are preferred.
Otherwise, the largest possible blue accumulation buffer of at least the
minimum size is preferred.

@item @code{GLX_ACCUM_ALPHA_SIZE}
Must be followed by a nonnegative minimum size specification. If this
value is zero, visuals with no alpha accumulation buffer are preferred.
Otherwise, the largest possible alpha accumulation buffer of at least
the minimum size is preferred.

@end table

@code{NULL} is returned if an undefined GLX attribute is encountered in
@var{attribList}.

@end deftypefun

@deftypefun void glXCopyContext dpy src dst mask
Copy state from one rendering context to another.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{src}
Specifies the source context.

@item @var{dst}
Specifies the destination context.

@item @var{mask}
Specifies which portions of @var{src} state are to be copied to
@var{dst}.

@end table

@code{glXCopyContext} copies selected groups of state variables from
@var{src} to @var{dst}. @var{mask} indicates which groups of state
variables are to be copied. @var{mask} contains the bitwise OR of the
same symbolic names that are passed to the GL command
@code{glPushAttrib}. The single symbolic constant
@code{GLX_ALL_ATTRIB_BITS} can be used to copy the maximum possible
portion of rendering state.

The copy can be done only if the renderers named by @var{src} and
@var{dst} share an address space. Two rendering contexts share an
address space if both are nondirect using the same server, or if both
are direct and owned by a single process. Note that in the nondirect
case it is not necessary for the calling threads to share an address
space, only for their related rendering contexts to share an address
space.

Not all values for GL state can be copied. For example, pixel pack and
unpack state, render mode state, and select and feedback state are not
copied. The state that can be copied is exactly the state that is
manipulated by the GL command @code{glPushAttrib}.

An implicit @code{glFlush} is done by @code{glXCopyContext} if @var{src}
is the current context for the calling thread.

@code{BadMatch} is generated if rendering contexts @var{src} and
@var{dst} do not share an address space or were not created with respect
to the same screen.

@code{BadAccess} is generated if @var{dst} is current to any thread
(including the calling thread) at the time @code{glXCopyContext} is
called.

@code{GLXBadCurrentWindow} is generated if @var{src} is the current
context and the current drawable is a window that is no longer valid.

@code{GLXBadContext} is generated if either @var{src} or @var{dst} is
not a valid GLX context.

@end deftypefun

@deftypefun GLXContext glXCreateContext dpy vis shareList direct
Create a new GLX rendering context.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{vis}
Specifies the visual that defines the frame buffer resources available
to the rendering context. It is a pointer to an @code{XVisualInfo}
structure, not a visual ID or a pointer to a @code{Visual}.

@item @var{shareList}
Specifies the context with which to share display lists. @code{NULL}
indicates that no sharing is to take place.

@item @var{direct}
Specifies whether rendering is to be done with a direct connection to
the graphics system if possible (@code{True}) or through the X server
(@code{False}).

@end table

@code{glXCreateContext} creates a GLX rendering context and returns its
handle. This context can be used to render into both windows and GLX
pixmaps. If @code{glXCreateContext} fails to create a rendering context,
@code{NULL} is returned.

If @var{direct} is @code{True}, then a direct rendering context is
created if the implementation supports direct rendering, if the
connection is to an X server that is local, and if a direct rendering
context is available. (An implementation may return an indirect context
when @var{direct} is @code{True}.) If @var{direct} is @code{False}, then
a rendering context that renders through the X server is always created.
Direct rendering provides a performance advantage in some
implementations. However, direct rendering contexts cannot be shared
outside a single process, and they may be unable to render to GLX
pixmaps.

If @var{shareList} is not @code{NULL}, then all display-list indexes and
definitions are shared by context @var{shareList} and by the newly
created context. An arbitrary number of contexts can share a single
display-list space. However, all rendering contexts that share a single
display-list space must themselves exist in the same address space. Two
rendering contexts share an address space if both are nondirect using
the same server, or if both are direct and owned by a single process.
Note that in the nondirect case, it is not necessary for the calling
threads to share an address space, only for their related rendering
contexts to share an address space.

If the GL version is 1.1 or greater, then all texture objects except
object 0 are shared by any contexts that share display lists.

@code{NULL} is returned if execution fails on the client side.

@code{BadMatch} is generated if the context to be created would not
share the address space or the screen of the context specified by
@var{shareList}.

@code{BadValue} is generated if @var{vis} is not a valid visual (for
example, if a particular GLX implementation does not support it).

@code{GLXBadContext} is generated if @var{shareList} is not a GLX
context and is not @code{NULL}.

@code{BadAlloc} is generated if the server does not have enough
resources to allocate the new context.

@end deftypefun

@deftypefun GLXPixmap glXCreateGLXPixmap dpy vis pixmap
Create an off-screen GLX rendering area.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{vis}
Specifies the visual that defines the structure of the rendering area.
It is a pointer to an @code{XVisualInfo} structure, not a visual ID or a
pointer to a @code{Visual}.

@item @var{pixmap}
Specifies the X pixmap that will be used as the front left color buffer
of the off-screen rendering area.

@end table

@code{glXCreateGLXPixmap} creates an off-screen rendering area and
returns its XID. Any GLX rendering context that was created with respect
to @var{vis} can be used to render into this off-screen area. Use
@code{glXMakeCurrent} to associate the rendering area with a GLX
rendering context.

The X pixmap identified by @var{pixmap} is used as the front left buffer
of the resulting off-screen rendering area. All other buffers specified
by @var{vis}, including color buffers other than the front left buffer,
are created without externally visible names. GLX pixmaps with
double-buffering are supported. However, @code{glXSwapBuffers} is
ignored by these pixmaps.

Some implementations may not support GLX pixmaps with direct rendering
contexts.

@code{BadMatch} is generated if the depth of @var{pixmap} does not match
the depth value reported by core X11 for @var{vis}, or if @var{pixmap}
was not created with respect to the same screen as @var{vis}.

@code{BadValue} is generated if @var{vis} is not a valid XVisualInfo
pointer (for example, if a particular GLX implementation does not
support this visual).

@code{BadPixmap} is generated if @var{pixmap} is not a valid pixmap.

@code{BadAlloc} is generated if the server cannot allocate the GLX
pixmap.

@end deftypefun

@deftypefun GLXContext glXCreateNewContext dpy config render_type share_list direct
Create a new GLX rendering context.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{config}
Specifies the GLXFBConfig structure with the desired attributes for the
context.

@item @var{render_type}
Specifies the type of the context to be created. Must be one of
@code{GLX_RGBA_TYPE} or @code{GLX_COLOR_INDEX_TYPE}.

@item @var{share_list}
Specifies the context with which to share display lists. @code{NULL}
indicates that no sharing is to take place.

@item @var{share_list}
Specifies whether rendering is to be done with a direct connection to
the graphics system if possible (@code{True}) or through the X server
(@code{False}).

@end table

@code{glXCreateNewContext} creates a GLX rendering context and returns
its handle. This context can be used to render into GLX windows,
pixmaps, or pixel buffers. If @code{glXCreateNewContext} fails to create
a rendering context, @code{NULL} is returned.

If @var{render_type} is @code{GLX_RGBA_TYPE}, then a context that
supports RGBA rendering is created. If @var{config} is
@code{GLX_COLOR_INDEX_TYPE}, then context supporting color-index
rendering is created.

If @var{render_type} is not @code{NULL}, then all display-list indexes
and definitions are shared by context @var{render_type} and by the newly
created context. An arbitrary number of contexts can share a single
display-list space. However, all rendering contexts that share a single
display-list space must themselves exist in the same address space. Two
rendering contexts share an address space if both are nondirect using
the same server, or if both are direct and owned by a single process.
Note that in the nondirect case, it is not necessary for the calling
threads to share an address space, only for their related rendering
contexts to share an address space.

If @var{share_list} is @code{True}, then a direct-rendering context is
created if the implementation supports direct rendering, if the
connection is to an X server that is local, and if a direct-rendering
context is available. (An implementation may return an indirect context
when @var{share_list} is @code{True}.) If @var{share_list} is
@code{False}, then a rendering context that renders through the X server
is always created. Direct rendering provides a performance advantage in
some implementations. However, direct-rendering contexts cannot be
shared outside a single process, and they may be unable to render to GLX
pixmaps.

@code{NULL} is returned if execution fails on the client side.

@code{GLXBadContext} is generated if @var{render_type} is not a GLX
context and is not @code{NULL}.

@code{GLXBadFBConfig} is generated if @var{config} is not a valid
GLXFBConfig.

@code{BadMatch} is generated if the context to be created would not
share the address space or the screen of the context specified by
@var{render_type}.

@code{BadAlloc} is generated if the server does not have enough
resources to allocate the new context.

@code{BadValue} is generated if @var{config} is not a valid visual (for
example, if a particular GLX implementation does not support it).

@end deftypefun

@deftypefun GLXPbuffer glXCreatePbuffer dpy config attrib_list
Create an off-screen rendering area.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{config}
Specifies a GLXFBConfig structure with the desired attributes for the
window.

@item @var{attrib_list}
Specifies a list of attribute value pairs, which must be terminated with
@code{None} or @code{NULL}. Accepted attributes are
@code{GLX_PBUFFER_WIDTH}, @code{GLX_PBUFFER_HEIGHT},
@code{GLX_PRESERVED_CONTENTS}, and @code{GLX_LARGEST_PBUFFER}.

@end table

@code{glXCreatePbuffer} creates an off-screen rendering area and returns
its XID. Any GLX rendering context that was created with respect to
@var{config} can be used to render into this window. Use
@code{glXMakeContextCurrent} to associate the rendering area with a GLX
rendering context.

The accepted attributes for a GLXPbuffer are:

@table @asis
@item @code{GLX_PBUFFER_WIDTH}
Specify the pixel width of the requested GLXPbuffer. The default value
is 0.

@item @code{GLX_PBUFFER_HEIGHT}
Specify the pixel height of the requested GLXPbuffer. The default value
is 0.

@item @code{GLX_LARGEST_PBUFFER}
Specify to obtain the largest available pixel buffer, if the requested
allocation would have failed. The width and height of the allocated
pixel buffer will never exceed the specified @code{GLX_PBUFFER_WIDTH} or
@code{GLX_PBUFFER_HEIGHT}, respectively. Use @code{glXQueryDrawable} to
retrieve the dimensions of the allocated pixel buffer. The default value
is @code{False}.

@item @code{GLX_PRESERVED_CONTENTS}
Specify if the contents of the pixel buffer should be preserved when a
resource conflict occurs. If set to @code{False}, the contents of the
pixel buffer may be lost at any time. If set to @code{True}, or not
specified in @var{attrib_list}, then the contents of the pixel buffer
will be preserved (most likely by copying the contents into main system
memory from the frame buffer). In either case, the client can register
(using @code{glXSelectEvent}, to receive pixel buffer clobber events
that are generated when the pbuffer contents have been preserved or
damaged.

@end table

GLXPbuffers contain the color and ancillary buffers specified by
@var{config}. It is possible to create a pixel buffer with back buffers
and to swap those buffers using @code{glXSwapBuffers}.

@code{BadAlloc} is generated if there are insufficient resources to
allocate the requested GLXPbuffer.

@code{GLXBadFBConfig} is generated if @var{config} is not a valid
GLXFBConfig.

@code{BadMatch} is generated if @var{config} does not support rendering
to pixel buffers (e.g., @code{GLX_DRAWABLE_TYPE} does not contain
@code{GLX_PBUFFER_BIT}).

@end deftypefun

@deftypefun GLXPixmap glXCreatePixmap dpy config pixmap attrib_list
Create an off-screen rendering area.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{config}
Specifies a GLXFBConfig structure with the desired attributes for the
window.

@item @var{pixmap}
Specifies the X pixmap to be used as the rendering area.

@item @var{attrib_list}
Currently unused. This must be set to @code{NULL} or be an empty list
(i.e., one in which the first element is @code{None}).

@end table

@code{glXCreatePixmap} creates an off-screen rendering area and returns
its XID. Any GLX rendering context that was created with respect to
@var{config} can be used to render into this window. Use
@code{glXMakeCurrent} to associate the rendering area with a GLX
rendering context.

@code{BadMatch} is generated if @var{pixmap} was not created with a
visual that corresponds to @var{config}.

@code{BadMatch} is generated if @var{config} does not support rendering
to windows (e.g., @code{GLX_DRAWABLE_TYPE} does not contain
@code{GLX_WINDOW_BIT}).

@code{BadWindow} is generated if @var{pixmap} is not a valid window XID.
@code{BadAlloc} is generated if there is already a GLXFBConfig
associated with @var{pixmap}.

@code{BadAlloc} is generated if the X server cannot allocate a new GLX
window.

@code{GLXBadFBConfig} is generated if @var{config} is not a valid
GLXFBConfig.



@end deftypefun

@deftypefun GLXWindow glXCreateWindow dpy config win attrib_list
Create an on-screen rendering area.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{config}
Specifies a GLXFBConfig structure with the desired attributes for the
window.

@item @var{win}
Specifies the X window to be used as the rendering area.

@item @var{attrib_list}
Currently unused. This must be set to @code{NULL} or be an empty list
(i.e., one in which the first element is @code{None}).

@end table

@code{glXCreateWindow} creates an on-screen rendering area from an
existing X window that was created with a visual matching @var{config}.
The XID of the GLXWindow is returned. Any GLX rendering context that was
created with respect to @var{config} can be used to render into this
window. Use @code{glXMakeContextCurrent} to associate the rendering area
with a GLX rendering context.

@code{BadMatch} is generated if @var{win} was not created with a visual
that corresponds to @var{config}.

@code{BadMatch} is generated if @var{config} does not support rendering
to windows (i.e., @code{GLX_DRAWABLE_TYPE} does not contain
@code{GLX_WINDOW_BIT}).

@code{BadWindow} is generated if @var{win} is not a valid pixmap XID.

@code{BadAlloc} is generated if there is already a GLXFBConfig
associated with @var{win}.

@code{BadAlloc} is generated if the X server cannot allocate a new GLX
window.

@code{GLXBadFBConfig} is generated if @var{config} is not a valid
GLXFBConfig.



@end deftypefun

@deftypefun void glXDestroyContext dpy ctx
Destroy a GLX context.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{ctx}
Specifies the GLX context to be destroyed.

@end table

If the GLX rendering context @var{ctx} is not current to any thread,
@code{glXDestroyContext} destroys it immediately. Otherwise, @var{ctx}
is destroyed when it becomes not current to any thread. In either case,
the resource ID referenced by @var{ctx} is freed immediately.

@code{GLXBadContext} is generated if @var{ctx} is not a valid GLX
context.

@end deftypefun

@deftypefun void glXDestroyGLXPixmap dpy pix
Destroy a GLX pixmap.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{pix}
Specifies the GLX pixmap to be destroyed.

@end table

If the GLX pixmap @var{pix} is not current to any client,
@code{glXDestroyGLXPixmap} destroys it immediately. Otherwise, @var{pix}
is destroyed when it becomes not current to any client. In either case,
the resource ID is freed immediately.

@code{GLXBadPixmap} is generated if @var{pix} is not a valid GLX pixmap.

@end deftypefun

@deftypefun void glXDestroyPbuffer dpy pbuf
Destroy an off-screen rendering area.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{pbuf}
Specifies the GLXPbuffer to be destroyed.

@end table

@code{glXDestroyPbuffer} destroys a GLXPbuffer created by
@code{glXCreatePbuffer}.

@code{GLXBadPbuffer} is generated if @var{pbuf} is not a valid
GLXPbuffer.

@end deftypefun

@deftypefun void glXDestroyPixmap dpy pixmap
Destroy an off-screen rendering area.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{pixmap}
Specifies the GLXPixmap to be destroyed.

@end table

@code{glXDestroyPixmap} destroys a GLXPixmap created by
@code{glXCreatePixmap}.

@code{GLXBadPixmap} is generated if @var{pixmap} is not a valid
GLXPixmap.

@end deftypefun

@deftypefun void glXDestroyWindow dpy win
Destroy an on-screen rendering area.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{win}
Specifies the GLXWindow to be destroyed.

@end table

@code{glXDestroyWindow} destroys a GLXWindow created by
@code{glXCreateWindow}.

@code{GLXBadWindow} is generated if @var{win} is not a valid GLXPixmap.

@end deftypefun

@deftypefun void glXFreeContextEXT dpy ctx
Free client-side memory for imported context.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{ctx}
Specifies a GLX rendering context.

@end table

@code{glXFreeContextEXT} frees the client-side part of a GLXContext that
was created with @code{glXImportContextEXT}. @code{glXFreeContextEXT}
does not free the server-side context information or the XID associated
with the server-side context.

@code{glXFreeContextEXT} is part of the @code{EXT_import_context}
extension, not part of the core GLX command set. If
_glxextstring(EXT_import_context) is included in the string returned by
@code{glXQueryExtensionsString}, when called with argument
@code{GLX_EXTENSIONS}, extension @code{EXT_vertex_array} is supported.

@code{GLXBadContext} is generated if @var{ctx} does not refer to a valid
context.

@end deftypefun

@deftypefun const-char-* glXGetClientString dpy name
Return a string describing the client.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{name}
Specifies which string is returned. The symbolic constants
@code{GLX_VENDOR}, @code{GLX_VERSION}, and @code{GLX_EXTENSIONS} are
accepted.

@end table

@code{glXGetClientString} returns a string describing some aspect of the
client library. The possible values for @var{name} are
@code{GLX_VENDOR}, @code{GLX_VERSION}, and @code{GLX_EXTENSIONS}. If
@var{name} is not set to one of these values, @code{glXGetClientString}
returns @code{NULL}. The format and contents of the vendor string is
implementation dependent.

The extensions string is null-terminated and contains a space-separated
list of extension names. (The extension names never contain spaces.) If
there are no extensions to GLX, then the empty string is returned.

The version string is laid out as follows:

<major_version.minor_version><space><vendor-specific info>

Both the major and minor portions of the version number are of arbitrary
length. The vendor-specific information is optional. However, if it is
present, the format and contents are implementation specific.

@end deftypefun

@deftypefun int glXGetConfig dpy vis attrib value
Return information about GLX visuals.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{vis}
Specifies the visual to be queried. It is a pointer to an
@code{XVisualInfo} structure, not a visual ID or a pointer to a
@code{Visual}.

@item @var{attrib}
Specifies the visual attribute to be returned.

@item @var{value}
Returns the requested value.

@end table

@code{glXGetConfig} sets @var{value} to the @var{attrib} value of
windows or GLX pixmaps created with respect to @var{vis}.
@code{glXGetConfig} returns an error code if it fails for any reason.
Otherwise, zero is returned.

@var{attrib} is one of the following:



@table @asis
@item @code{GLX_USE_GL}
@code{True} if OpenGL rendering is supported by this visual,
@code{False} otherwise.

@item @code{GLX_BUFFER_SIZE}
Number of bits per color buffer. For RGBA visuals,
@code{GLX_BUFFER_SIZE} is the sum of @code{GLX_RED_SIZE},
@code{GLX_GREEN_SIZE}, @code{GLX_BLUE_SIZE}, and @code{GLX_ALPHA_SIZE}.
For color index visuals, @code{GLX_BUFFER_SIZE} is the size of the color
indexes.

@item @code{GLX_LEVEL}
Frame buffer level of the visual. Level zero is the default frame
buffer. Positive levels correspond to frame buffers that overlay the
default buffer, and negative levels correspond to frame buffers that
underlay the default buffer.

@item @code{GLX_RGBA}
@code{True} if color buffers store red, green, blue, and alpha values.
@code{False} if they store color indexes.

@item @code{GLX_DOUBLEBUFFER}
@code{True} if color buffers exist in front/back pairs that can be
swapped, @code{False} otherwise.

@item @code{GLX_STEREO}
@code{True} if color buffers exist in left/right pairs, @code{False}
otherwise.

@item @code{GLX_AUX_BUFFERS}
Number of auxiliary color buffers that are available. Zero indicates
that no auxiliary color buffers exist.

@item @code{GLX_RED_SIZE}
Number of bits of red stored in each color buffer. Undefined if
@code{GLX_RGBA} is @code{False}.

@item @code{GLX_GREEN_SIZE}
Number of bits of green stored in each color buffer. Undefined if
@code{GLX_RGBA} is @code{False}.

@item @code{GLX_BLUE_SIZE}
Number of bits of blue stored in each color buffer. Undefined if
@code{GLX_RGBA} is @code{False}.

@item @code{GLX_ALPHA_SIZE}
Number of bits of alpha stored in each color buffer. Undefined if
@code{GLX_RGBA} is @code{False}.

@item @code{GLX_DEPTH_SIZE}
Number of bits in the depth buffer.

@item @code{GLX_STENCIL_SIZE}
Number of bits in the stencil buffer.

@item @code{GLX_ACCUM_RED_SIZE}
Number of bits of red stored in the accumulation buffer.

@item @code{GLX_ACCUM_GREEN_SIZE}
Number of bits of green stored in the accumulation buffer.

@item @code{GLX_ACCUM_BLUE_SIZE}
Number of bits of blue stored in the accumulation buffer.

@item @code{GLX_ACCUM_ALPHA_SIZE}
Number of bits of alpha stored in the accumulation buffer.

@end table

The X protocol allows a single visual ID to be instantiated with
different numbers of bits per pixel. Windows or GLX pixmaps that will be
rendered with OpenGL, however, must be instantiated with a color buffer
depth of @code{GLX_BUFFER_SIZE}.

Although a GLX implementation can export many visuals that support GL
rendering, it must support at least one RGBA visual. This visual must
have at least one color buffer, a stencil buffer of at least 1 bit, a
depth buffer of at least 12 bits, and an accumulation buffer. Alpha
bitplanes are optional in this visual. However, its color buffer size
must be as great as that of the deepest @code{TrueColor},
@code{DirectColor}, @code{PseudoColor}, or @code{StaticColor} visual
supported on level zero, and it must itself be made available on level
zero.

In addition, if the X server exports a @code{PseudoColor} or
@code{StaticColor} visual on framebuffer level 0, a color index visual
is also required on that level. It must have at least one color buffer,
a stencil buffer of at least 1 bit, and a depth buffer of at least 12
bits. This visual must have as many color bitplanes as the deepest
@code{PseudoColor} or @code{StaticColor} visual supported on level 0.

Applications are best written to select the visual that most closely
meets their requirements. Creating windows or GLX pixmaps with
unnecessary buffers can result in reduced rendering performance as well
as poor resource allocation.

@code{GLX_NO_EXTENSION} is returned if @var{dpy} does not support the
GLX extension.

@code{GLX_BAD_SCREEN} is returned if the screen of @var{vis} does not
correspond to a screen.

@code{GLX_BAD_ATTRIBUTE} is returned if @var{attrib} is not a valid GLX
attribute.

@code{GLX_BAD_VISUAL} is returned if @var{vis} doesn't support GLX and
an attribute other than @code{GLX_USE_GL} is requested.

@end deftypefun

@deftypefun GLXContextID glXGetContextIDEXT ctx
Get the XID for a context..

@table @asis
@item @var{ctx}
Specifies a GLX rendering context.

@end table

@code{glXGetContextIDEXT} returns the XID associated with a GLXContext.

No round trip is forced to the server; unlike most X calls that return a
value, @code{glXGetContextIDEXT} does not flush any pending events.

@code{glXGetContextIDEXT} is part of the @code{EXT_import_context}
extension, not part of the core GLX command set. If
_glxextstring(EXT_import_context) is included in the string returned by
@code{glXQueryExtensionsString}, when called with argument
@code{GLX_EXTENSIONS}, extension @code{EXT_import_context} is supported.

@code{GLXBadContext} is generated if @var{ctx} does not refer to a valid
context.

@end deftypefun

@deftypefun GLXContext glXGetCurrentContext 
Return the current context.

@code{glXGetCurrentContext} returns the current context, as specified by
@code{glXMakeCurrent}. If there is no current context, @code{NULL} is
returned.

@code{glXGetCurrentContext} returns client-side information. It does not
make a round trip to the server.



@end deftypefun

@deftypefun Display-* glXGetCurrentDisplay 
Get display for current context.

@code{glXGetCurrentDisplay} returns the display for the current context.
If no context is current, @code{NULL} is returned.

@code{glXGetCurrentDisplay} returns client-side information. It does not
make a round-trip to the server, and therefore does not flush any
pending events.

@end deftypefun

@deftypefun GLXDrawable glXGetCurrentDrawable 
Return the current drawable.

@code{glXGetCurrentDrawable} returns the current drawable, as specified
by @code{glXMakeCurrent}. If there is no current drawable, @code{None}
is returned.

@code{glXGetCurrentDrawable} returns client-side information. It does
not make a round trip to the server.

@end deftypefun

@deftypefun GLXDrawable glXGetCurrentReadDrawable 
Return the current drawable.

@code{glXGetCurrentReadDrawable} returns the current read drawable, as
specified by @code{read} parameter of @code{glXMakeContextCurrent}. If
there is no current drawable, @code{None} is returned.

@code{glXGetCurrentReadDrawable} returns client-side information. It
does not make a round-trip to the server.

@end deftypefun

@deftypefun int glXGetFBConfigAttrib dpy config attribute value
Return information about a GLX frame buffer configuration.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{config}
Specifies the GLX frame buffer configuration to be queried.

@item @var{attribute}
Specifies the attribute to be returned.

@item @var{value}
Returns the requested value.

@end table

@code{glXGetFBConfigAttrib} sets @var{value} to the @var{attribute}
value of GLX drawables created with respect to @var{config}.
@code{glXGetFBConfigAttrib} returns an error code if it fails for any
reason. Otherwise, @code{Success} is returned.

@var{attribute} is one of the following:



@table @asis
@item @code{GLX_FBCONFIG_ID}
XID of the given GLXFBConfig.

@item @code{GLX_BUFFER_SIZE}


Number of bits per color buffer. If the frame buffer configuration
supports RGBA contexts, then @code{GLX_BUFFER_SIZE} is the sum of
@code{GLX_RED_SIZE}, @code{GLX_GREEN_SIZE}, @code{GLX_BLUE_SIZE}, and
@code{GLX_ALPHA_SIZE}. If the frame buffer configuration supports only
color index contexts, @code{GLX_BUFFER_SIZE} is the size of the color
indexes.

@item @code{GLX_LEVEL}


Frame buffer level of the configuration. Level zero is the default frame
buffer. Positive levels correspond to frame buffers that overlay the
default buffer, and negative levels correspond to frame buffers that
underlie the default buffer.

@item @code{GLX_DOUBLEBUFFER}


@code{True} if color buffers exist in front/back pairs that can be
swapped, @code{False} otherwise.

@item @code{GLX_STEREO}


@code{True} if color buffers exist in left/right pairs, @code{False}
otherwise.

@item @code{GLX_AUX_BUFFERS}


Number of auxiliary color buffers that are available. Zero indicates
that no auxiliary color buffers exist.

@item @code{GLX_RED_SIZE}


Number of bits of red stored in each color buffer. Undefined if RGBA
contexts are not supported by the frame buffer configuration.

@item @code{GLX_GREEN_SIZE}


Number of bits of green stored in each color buffer. Undefined if RGBA
contexts are not supported by the frame buffer configuration.

@item @code{GLX_BLUE_SIZE}


Number of bits of blue stored in each color buffer. Undefined if RGBA
contexts are not supported by the frame buffer configuration.

@item @code{GLX_ALPHA_SIZE}


Number of bits of alpha stored in each color buffer. Undefined if RGBA
contexts are not supported by the frame buffer configuration.

@item @code{GLX_DEPTH_SIZE}


Number of bits in the depth buffer.

@item @code{GLX_STENCIL_SIZE}


Number of bits in the stencil buffer.

@item @code{GLX_ACCUM_RED_SIZE}


Number of bits of red stored in the accumulation buffer.

@item @code{GLX_ACCUM_GREEN_SIZE}


Number of bits of green stored in the accumulation buffer.

@item @code{GLX_ACCUM_BLUE_SIZE}


Number of bits of blue stored in the accumulation buffer.

@item @code{GLX_ACCUM_ALPHA_SIZE}


Number of bits of alpha stored in the accumulation buffer.

@item @code{GLX_RENDER_TYPE}


Mask indicating what type of GLX contexts can be made current to the
frame buffer configuration. Valid bits are @code{GLX_RGBA_BIT} and
@code{GLX_COLOR_INDEX_BIT}.

@item @code{GLX_DRAWABLE_TYPE}


Mask indicating what drawable types the frame buffer configuration
supports. Valid bits are @code{GLX_WINDOW_BIT}, @code{GLX_PIXMAP_BIT},
and @code{GLX_PBUFFER_BIT}.

@item @code{GLX_X_RENDERABLE}


@code{True} if drawables created with the frame buffer configuration can
be rendered to by X.

@item @code{GLX_VISUAL_ID}


XID of the corresponding visual, or zero if there is no associated
visual (i.e., if @code{GLX_X_RENDERABLE} is @code{False} or
@code{GLX_DRAWABLE_TYPE} does not have the @code{GLX_WINDOW_BIT} bit
set).

@item @code{GLX_X_VISUAL_TYPE}


Visual type of associated visual. The returned value will be one of:
@code{GLX_TRUE_COLOR}, @code{GLX_DIRECT_COLOR}, @code{GLX_PSEUDO_COLOR},
@code{GLX_STATIC_COLOR}, @code{GLX_GRAY_SCALE}, @code{GLX_STATIC_GRAY},
or @code{GLX_NONE}, if there is no associated visual (i.e., if
@code{GLX_X_RENDERABLE} is @code{False} or @code{GLX_DRAWABLE_TYPE} does
not have the @code{GLX_WINDOW_BIT} bit set).

@item @code{GLX_CONFIG_CAVEAT}


One of @code{GLX_NONE}, @code{GLX_SLOW_CONFIG}, or
@code{GLX_NON_CONFORMANT_CONFIG}, indicating that the frame buffer
configuration has no caveats, some aspect of the frame buffer
configuration runs slower than other frame buffer configurations, or
some aspect of the frame buffer configuration is nonconformant,
respectively.

@item @code{GLX_TRANSPARENT_TYPE}


One of @code{GLX_NONE}, @code{GLX_TRANSPARENT_RGB},
@code{GLX_TRANSPARENT_INDEX}, indicating that the frame buffer
configuration is opaque, is transparent for particular values of red,
green, and blue, or is transparent for particular index values,
respectively.

@item @code{GLX_TRANSPARENT_INDEX_VALUE}


Integer value between 0 and the maximum frame buffer value for indices,
indicating the transparent index value for the frame buffer
configuration. Undefined if @code{GLX_TRANSPARENT_TYPE} is not
@code{GLX_TRANSPARENT_INDEX}.

@item @code{GLX_TRANSPARENT_RED_VALUE}


Integer value between 0 and the maximum frame buffer value for red,
indicating the transparent red value for the frame buffer configuration.
Undefined if @code{GLX_TRANSPARENT_TYPE} is not
@code{GLX_TRANSPARENT_RGB}.

@item @code{GLX_TRANSPARENT_GREEN_VALUE}


Integer value between 0 and the maximum frame buffer value for green,
indicating the transparent green value for the frame buffer
configuration. Undefined if @code{GLX_TRANSPARENT_TYPE} is not
@code{GLX_TRANSPARENT_RGB}.

@item @code{GLX_TRANSPARENT_BLUE_VALUE}


Integer value between 0 and the maximum frame buffer value for blue,
indicating the transparent blue value for the frame buffer
configuration. Undefined if @code{GLX_TRANSPARENT_TYPE} is not
@code{GLX_TRANSPARENT_RGB}.

@item @code{GLX_TRANSPARENT_ALPHA_VALUE}


Integer value between 0 and the maximum frame buffer value for alpha,
indicating the transparent blue value for the frame buffer
configuration. Undefined if @code{GLX_TRANSPARENT_TYPE} is not
@code{GLX_TRANSPARENT_RGB}.

@item @code{GLX_MAX_PBUFFER_WIDTH}


The maximum width that can be specified to @code{glXCreatePbuffer}.

@item @code{GLX_MAX_PBUFFER_HEIGHT}


The maximum height that can be specified to @code{glXCreatePbuffer}.

@item @code{GLX_MAX_PBUFFER_PIXELS}


The maximum number of pixels (width times height) for a pixel buffer.
Note that this value may be less than @code{GLX_MAX_PBUFFER_WIDTH} times
@code{GLX_MAX_PBUFFER_HEIGHT}. Also, this value is static and assumes
that no other pixel buffers or X resources are contending for the frame
buffer memory. As a result, it may not be possible to allocate a pixel
buffer of the size given by @code{GLX_MAX_PBUFFER_PIXELS}.

@end table

Applications should choose the frame buffer configuration that most
closely meets their requirements. Creating windows, GLX pixmaps, or GLX
pixel buffers with unnecessary buffers can result in reduced rendering
performance as well as poor resource allocation.

@code{GLX_NO_EXTENSION} is returned if @var{dpy} does not support the
GLX extension. @code{GLX_BAD_ATTRIBUTE} is returned if @var{attribute}
is not a valid GLX attribute.

@end deftypefun

@deftypefun GLXFBConfig-* glXGetFBConfigs dpy screen nelements
List all GLX frame buffer configurations for a given screen.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{screen}
Specifies the screen number.

@item @var{nelements}
Returns the number of GLXFBConfigs returned.

@end table

@code{glXGetFBConfigs} returns a list of all GLXFBConfigs available on
the screen specified by @var{screen}. Use @code{glXGetFBConfigAttrib} to
obtain attribute values from a specific GLXFBConfig.

@end deftypefun

@deftypefun void(*)() glXGetProcAddress procName
Obtain a pointer to an OpenGL or GLX function.

@table @asis
@item @var{procName}
Specifies the name of the OpenGL or GLX function whose address is to be
returned.

@end table

@code{glXGetProcAddress} returns the address of the function specified
in @var{procName}. This is necessary in environments where the OpenGL
link library exports a different set of functions than the runtime
library.

@end deftypefun

@deftypefun void glXGetSelectedEvent dpy draw event_mask
Returns GLX events that are selected for a window or a GLX pixel buffer.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{draw}
Specifies a GLX drawable. Must be a GLX pixel buffer or a window.

@item @var{event_mask}
Returns the events that are selected for @var{draw}.

@end table

@code{glXGetSelectedEvent} returns in @var{event_mask} the events
selected for @var{draw}.

@code{GLXBadDrawable} is generated if @var{draw} is not a valid window
or a valid GLX pixel buffer.

@end deftypefun

@deftypefun XVisualInfo-* glXGetVisualFromFBConfig dpy config
Return visual that is associated with the frame buffer configuration.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{config}
Specifies the GLX frame buffer configuration.

@end table

If @var{config} is a valid GLX frame buffer configuration and it has an
associated X Visual, then information describing that visual is
returned; otherwise @code{NULL} is returned. Use @code{XFree} to free
the data returned.

Returns @code{NULL} if @var{config} is not a valid GLXFBConfig.

@end deftypefun

@deftypefun GLXContext glXImportContextEXT dpy contextID
Import another process's indirect rendering context..

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{contextID}
Specifies a GLX rendering context.

@end table

@code{glXImportContextEXT} creates a GLXContext given the XID of an
existing GLXContext. It may be used in place of @code{glXCreateContext},
to share another process's indirect rendering context.

Only the server-side context information can be shared between X
clients; client-side state, such as pixel storage modes, cannot be
shared. Thus, @code{glXImportContextEXT} must allocate memory to store
client-side information. This memory is freed by calling
@code{glXFreeContextEXT}.

This call does not create a new XID. It merely makes an existing object
available to the importing client (Display *). Like any XID, it goes
away when the creating client drops its connection or the ID is
explicitly deleted. Note that this is when the XID goes away. The object
goes away when the XID goes away AND the context is not current to any
thread.

If @var{contextID} refers to a direct rendering context then no error is
generated but @code{glXImportContextEXT} returns NULL.

@code{glXImportContextEXT} is part of the @code{EXT_import_context}
extension, not part of the core GLX command set. If
_glxextstring(EXT_import_context) is included in the string returned by
@code{glXQueryExtensionsString}, when called with argument
@code{GLX_EXTENSIONS}, extension @code{EXT_import_context} is supported.

@code{GLXBadContext} is generated if @var{contextID} does not refer to a
valid context.

@end deftypefun

@deftypefun Bool glXIsDirect dpy ctx
Indicate whether direct rendering is enabled.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{ctx}
Specifies the GLX context that is being queried.

@end table

@code{glXIsDirect} returns @code{True} if @var{ctx} is a direct
rendering context, @code{False} otherwise. Direct rendering contexts
pass rendering commands directly from the calling process's address
space to the rendering system, bypassing the X server. Nondirect
rendering contexts pass all rendering commands to the X server.

@code{GLXBadContext} is generated if @var{ctx} is not a valid GLX
context.

@end deftypefun

@deftypefun Bool glXMakeContextCurrent display draw read ctx
Attach a GLX context to a GLX drawable.

@table @asis
@item @var{display}
Specifies the connection to the X server.

@item @var{draw}
Specifies a GLX drawable to render into. Must be an XID representing a
GLXWindow, GLXPixmap, or GLXPbuffer.

@item @var{read}
Specifies a GLX drawable to read from. Must be an XID representing a
GLXWindow, GLXPixmap, or GLXPbuffer.

@item @var{ctx}
Specifies the GLX context to be bound to @var{read} and @var{ctx}.

@end table

@code{glXMakeContextCurrent} binds @var{ctx} to the current rendering
thread and to the @var{draw} and @var{read} GLX drawables. @var{draw}
and @var{read} may be the same.

@var{draw} is used for all OpenGL operations except:

Any pixel data that are read based on the value of
@code{GLX_READ_BUFFER}. Note that accumulation operations use the value
of @code{GLX_READ_BUFFER}, but are not allowed unless @var{draw} is
identical to @var{read}.

Any depth values that are retrieved by @code{glReadPixels} or
@code{glCopyPixels}.

Any stencil values that are retrieved by @code{glReadPixels} or
@code{glCopyPixels}.

Frame buffer values are taken from @var{draw}.

If the current rendering thread has a current rendering context, that
context is flushed and replaced by @var{ctx}.

The first time that @var{ctx} is made current, the viewport and scissor
dimensions are set to the size of the @var{draw} drawable. The viewport
and scissor are not modified when @var{ctx} is subsequently made
current.

To release the current context without assigning a new one, call
@code{glXMakeContextCurrent} with @var{draw} and @var{read} set to
@code{None} and @var{ctx} set to @code{NULL}.

@code{glXMakeContextCurrent} returns @code{True} if it is successful,
@code{False} otherwise. If @code{False} is returned, the previously
current rendering context and drawable (if any) remain unchanged.

@code{BadMatch} is generated if @var{draw} and @var{read} are not
compatible.

@code{BadAccess} is generated if @var{ctx} is current to some other
thread.

@code{GLXContextState} is generated if there is a current rendering
context and its render mode is either @code{GLX_FEEDBACK} or
@code{GLX_SELECT}.

@code{GLXBadContext} is generated if @var{ctx} is not a valid GLX
rendering context.

@code{GLXBadDrawable} is generated if @var{draw} or @var{read} is not a
valid GLX drawable.

@code{GLXBadWindow} is generated if the underlying X window for either
@var{draw} or @var{read} is no longer valid.

@code{GLXBadCurrentDrawable} is generated if the previous context of the
calling thread has unflushed commands and the previous drawable is no
longer valid.

@code{BadAlloc} is generated if the X server does not have enough
resources to allocate the buffers.

@code{BadMatch} is generated if:

@var{draw} and @var{read} cannot fit into frame buffer memory
simultaneously.

@var{draw} or @var{read} is a GLXPixmap and @var{ctx} is a
direct-rendering context.

@var{draw} or @var{read} is a GLXPixmap and @var{ctx} was previously
bound to a GLXWindow or GLXPbuffer.

@var{draw} or @var{read} is a GLXWindow or GLXPbuffer and @var{ctx} was
previously bound to a GLXPixmap.

@end deftypefun

@deftypefun Bool glXMakeCurrent dpy drawable ctx
Attach a GLX context to a window or a GLX pixmap.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{drawable}
Specifies a GLX drawable. Must be either an X window ID or a GLX pixmap
ID.

@item @var{ctx}
Specifies a GLX rendering context that is to be attached to
@var{drawable}.

@end table

@code{glXMakeCurrent} does two things: It makes @var{ctx} the current
GLX rendering context of the calling thread, replacing the previously
current context if there was one, and it attaches @var{ctx} to a GLX
drawable, either a window or a GLX pixmap. As a result of these two
actions, subsequent GL rendering calls use rendering context @var{ctx}
to modify GLX drawable @var{drawable} (for reading and writing). Because
@code{glXMakeCurrent} always replaces the current rendering context with
@var{ctx}, there can be only one current context per thread.

Pending commands to the previous context, if any, are flushed before it
is released.

The first time @var{ctx} is made current to any thread, its viewport is
set to the full size of @var{drawable}. Subsequent calls by any thread
to @code{glXMakeCurrent} with @var{ctx} have no effect on its viewport.

To release the current context without assigning a new one, call
@code{glXMakeCurrent} with @var{drawable} set to @code{None} and
@var{ctx} set to @code{NULL}.

@code{glXMakeCurrent} returns @code{True} if it is successful,
@code{False} otherwise. If @code{False} is returned, the previously
current rendering context and drawable (if any) remain unchanged.

@code{BadMatch} is generated if @var{drawable} was not created with the
same X screen and visual as @var{ctx}. It is also generated if
@var{drawable} is @code{None} and @var{ctx} is not @code{NULL}.

@code{BadAccess} is generated if @var{ctx} was current to another thread
at the time @code{glXMakeCurrent} was called.

@code{GLXBadDrawable} is generated if @var{drawable} is not a valid GLX
drawable.

@code{GLXBadContext} is generated if @var{ctx} is not a valid GLX
context.

@code{GLXBadContextState} is generated if @code{glXMakeCurrent} is
executed between the execution of @code{glBegin} and the corresponding
execution of @code{glEnd}.

@code{GLXBadContextState} is also generated if the rendering context
current to the calling thread has GL renderer state @code{GLX_FEEDBACK}
or @code{GLX_SELECT}.

@code{GLXBadCurrentWindow} is generated if there are pending GL commands
for the previous context and the current drawable is a window that is no
longer valid.

@code{BadAlloc} may be generated if the server has delayed allocation of
ancillary buffers until @code{glXMakeCurrent} is called, only to find
that it has insufficient resources to complete the allocation.

@end deftypefun

@deftypefun int glXQueryContextInfoEXT dpy ctx attribute value
Query context information.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{ctx}
Specifies a GLX rendering context.

@item @var{attribute}
Specifies that a context parameter should be retrieved. Must be one of
@code{GLX_SHARED_CONTEXT_EXT}, @code{GLX_VISUAL_ID_EXT}, or
@code{GLX_SCREEN_EXT}.

@item @var{value}
Contains the return value for @var{attribute}.

@end table

@code{glXQueryContextInfoEXT} sets @var{value} to the value of
@var{attribute} with respect to @var{ctx}. @code{glXQueryContextInfoEXT}
returns an error code if it fails for any reason. Otherwise,
@code{Success} is returned.

@var{attribute} may be one of the following:

@table @asis
@item @code{GLX_SHARED_CONTEXT_EXT}
Returns the XID of the share list context associated with @var{ctx} at
its creation.

@item @code{GLX_VISUAL_ID_EXT}
Returns the XID of the GLX Visual associated with @var{ctx}.

@item @code{GLX_SCREEN_EXT}
Returns the screen number associated with @var{ctx}.

@end table

This call may cause a round-trip to the server.

@code{glXQueryContextInfoEXT} is part of the @code{EXT_import_context}
extension, not part of the core GLX command set. If
_glxextstring(EXT_import_context) is included in the string returned by
@code{glXQueryExtensionsString}, when called with argument
@code{GLX_EXTENSIONS}, extension @code{EXT_import_context} is supported.

@code{GLXBadContext} is generated if @var{ctx} does not refer to a valid
context.

@code{GLX_BAD_ATTRIBUTE} is returned if @var{attribute} is not a valid
GLX context attribute.

fred @code{GLX_BAD_CONTEXT} is returned if @var{attribute} is not a
valid context.

@end deftypefun

@deftypefun int glXQueryContext dpy ctx attribute value
Query context information.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{ctx}
Specifies a GLX rendering context.

@item @var{attribute}
Specifies that a context parameter should be retrieved. Must be one of
@code{GLX_FBCONFIG_ID}, @code{GLX_RENDER_TYPE}, or @code{GLX_SCREEN}.

@item @var{value}
Contains the return value for @var{attribute}.

@end table

@code{glXQueryContext} sets @var{value} to the value of @var{attribute}
with respect to @var{ctx}. @var{attribute} may be one of the following:

@table @asis
@item @code{GLX_FBCONFIG_ID}
Returns the XID of the GLXFBConfig associated with @var{ctx}.

@item @code{GLX_RENDER_TYPE}
Returns the rendering type supported by @var{ctx}.

@item @code{GLX_SCREEN}
Returns the screen number associated with @var{ctx}.

@end table

@code{Success} is returned unless @var{attribute} is not a valid GLX
context attribute, in which case @code{GLX_BAD_ATTRIBUTE} is returned.

This call may cause a round-trip to the server.

@code{GLXBadContext} is generated if @var{ctx} does not refer to a valid
context.

@end deftypefun

@deftypefun int glXQueryDrawable dpy draw attribute value
Returns an attribute assoicated with a GLX drawable.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{draw}
Specifies the GLX drawable to be queried.

@item @var{attribute}
Specifies the attribute to be returned. Must be one of @code{GLX_WIDTH},
@code{GLX_HEIGHT}, @code{GLX_PRESERVED_CONTENTS},
@code{GLX_LARGEST_PBUFFER}, or @code{GLX_FBCONFIG_ID}.

@item @var{value}
Contains the return value for @var{attribute}.

@end table

@code{glXQueryDrawable} sets @var{value} to the value of @var{attribute}
with respect to the GLXDrawable @var{draw}.

@var{attribute} may be one of the following:

@table @asis
@item @code{GLX_WIDTH}
Returns the width of @var{ctx}.

@item @code{GLX_HEIGHT}
Returns the height of @var{ctx}.

@item @code{GLX_PRESERVED_CONTENTS}
Returns @code{True} if the contents of a GLXPbuffer are preserved when a
resource conflict occurs; @code{False} otherwise.

@item @code{GLX_LARGEST_PBUFFER}
Returns the value set when @code{glXCreatePbuffer} was called to create
the GLXPbuffer. If @code{False} is returned, then the call to
@code{glXCreatePbuffer} will fail to create a GLXPbuffer if the
requested size is larger than the implementation maximum or available
resources. If @code{True} is returned, a GLXPbuffer of the maximum
availble size (if less than the requested width and height) is created.

@item @code{GLX_FBCONFIG_ID}
Returns the XID for @var{draw}.

@end table

If @var{draw} is a GLXWindow or GLXPixmap and @var{attribute} is set to
@code{GLX_PRESERVED_CONTENTS} or @code{GLX_LARGETST_PBUFFER}, the
contents of @var{value} are undefined. If @var{attribute} is not one of
the attributes listed above, the contents of @var{value} are unedfined.

A @code{GLXBadDrawable} is generated if @var{draw} is not a valid
GLXDrawable.

@end deftypefun

@deftypefun const-char-* glXQueryExtensionsString dpy screen
Return list of supported extensions.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{screen}
Specifies the screen number.

@end table

@code{glXQueryExtensionsString} returns a pointer to a string describing
which GLX extensions are supported on the connection. The string is
null-terminated and contains a space-separated list of extension names.
(The extension names themselves never contain spaces.) If there are no
extensions to GLX, then the empty string is returned.

@end deftypefun

@deftypefun Bool glXQueryExtension dpy errorBase eventBase
Indicate whether the GLX extension is supported.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{errorBase}
Returns the base error code of the GLX server extension.

@item @var{eventBase}
Returns the base event code of the GLX server extension.

@end table

@code{glXQueryExtension} returns @code{True} if the X server of
connection @var{dpy} supports the GLX extension, @code{False} otherwise.
If @code{True} is returned, then @var{errorBase} and @var{eventBase}
return the error base and event base of the GLX extension. These values
should be added to the constant error and event values to determine the
actual event or error values. Otherwise, @var{errorBase} and
@var{eventBase} are unchanged.

@var{errorBase} and @var{eventBase} do not return values if they are
specified as @code{NULL}.

@end deftypefun

@deftypefun const-char-* glXQueryServerString dpy screen name
Return string describing the server.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{screen}
Specifies the screen number.

@item @var{name}
Specifies which string is returned: one of @code{GLX_VENDOR},
@code{GLX_VERSION}, or @code{GLX_EXTENSIONS}.

@end table

@code{glXQueryServerString} returns a pointer to a static,
null-terminated string describing some aspect of the server's GLX
extension. The possible values for @var{name} and the format of the
strings is the same as for @code{glXGetClientString}. If @var{name} is
not set to a recognized value, @code{NULL} is returned.

@end deftypefun

@deftypefun Bool glXQueryVersion dpy major minor
Return the version numbers of the GLX extension.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{major}
Returns the major version number of the GLX server extension.

@item @var{minor}
Returns the minor version number of the GLX server extension.

@end table

@code{glXQueryVersion} returns the major and minor version numbers of
the GLX extension implemented by the server associated with connection
@var{dpy}. Implementations with the same major version number are upward
compatible, meaning that the implementation with the higher minor number
is a superset of the version with the lower minor number.

@var{major} and @var{minor} do not return values if they are specified
as @code{NULL}.

@code{glXQueryVersion} returns @code{False} if it fails, @code{True}
otherwise.

@var{major} and @var{minor} are not updated when @code{False} is
returned.

@end deftypefun

@deftypefun void glXSelectEvent dpy draw event_mask
Select GLX events for a window or a GLX pixel buffer.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{draw}
Specifies a GLX drawable. Must be a GLX pixel buffer or a window.

@item @var{event_mask}
Specifies the events to be returned for @var{draw}.

@end table

@code{glXSelectEvent} sets the GLX event mask for a GLX pixel buffer or
a window. Calling @code{glXSelectEvent} overrides any previous event
mask that was set by the client for @var{draw}. Note that it does not
affect the event masks that other clients may have specified for
@var{draw} since each client rendering to @var{draw} has a separate
event mask for it.

Currently, only one GLX event, @code{GLX_PBUFFER_CLOBBER_MASK}, can be
selected. The following data is returned to the client when a
@code{GLX_PBUFFER_CLOBBER_MASK} event occurs:

typedef struct @{

@table @asis
@item 
int @var{event_type}; 
/* GLX_DAMAGED or GLX_SAVED */

@item 
int @var{draw_type}; 
/* GLX_WINDOW or GLX_PBUFFER */

@item 
unsigned long @var{serial}; 
/* # of last request processed by server */

@item 
Bool @var{send_event}; 
/* true if this came for SendEvent request */

@item 
Display @var{*display}; 
/* display the event was read from */

@item 
GLXDrawable @var{drawable}; 
/* i.d. of Drawable */

@item 
unsigned int @var{buffer_mask}; 
/* mask indicating affected buffers */

@item 
int @var{x, y}; 


@item 
int @var{width, height}; 


@item 
int @var{count}; 
/* if nonzero, at least this many more */

@end table

@} GLXPbufferClobberEvent; The valid bit masks used in @var{buffer_mask}
are:



@table @asis
@item @strong{Bitmask}
@strong{Corresponding Buffer}

@item @code{GLX_FRONT_LEFT_BUFFER_BIT}
Front left color buffer

@item @code{GLX_FRONT_RIGHT_BUFFER_BIT}
Front right color buffer

@item @code{GLX_BACK_LEFT_BUFFER_BIT}
Back left color buffer

@item @code{GLX_BACK_RIGHT_BUFFER_BIT}
Back right color buffer

@item @code{GLX_AUX_BUFFERS_BIT}
Auxiliary buffer

@item @code{GLX_DEPTH_BUFFER_BIT}
Depth buffer

@item @code{GLX_STENCIL_BUFFER_BIT}
Stencil buffer

@item @code{GLX_ACCUM_BUFFER_BIT}
Accumulation buffer

@end table

A single X server operation can cause several buffer clobber events to
be sent. (e.g., a single GLX pixel buffer may be damaged and cause
multiple buffer clobber events to be generated). Each event specifies
one region of the GLX drawable that was affected by the X Server
operation. The @var{buffer_mask} field indicates which color buffers and
ancillary buffers were affected. All the buffer clobber events generated
by a single X server action are guaranteed to be contiguous in the event
queue. The conditions under which this event is generated and the
@var{event_type} varies, depending on the type of the GLX drawable.

When the @code{GLX_AUX_BUFFERS_BIT} is set in @var{buffer_mask}, then
@var{aux_buffer} is set to indicate which buffer was affected. If more
than one aux buffer was affected, then additional events are generated
as part of the same contiguous event group. Each additional event will
have only the @code{GLX_AUX_BUFFERS_BIT} set in @var{buffer_mask}, and
the @var{aux_buffer} field will be set appropriately. For nonstereo
drawables, @code{GLX_FRONT_LEFT_BUFFER_BIT} and
@code{GLX_BACK_LEFT_BUFFER_BIT} are used to specify the front and back
color buffers.

For preserved GLX pixel buffers, a buffer clobber event with type
@code{GLX_SAVED} is generated whenever the contents of the GLX pixel
buffer is moved out of offscreen memory. The event(s) describes which
portions of the GLX pixel buffer were affected. Clients who receive many
buffer clobber events, referring to different save actions, should
consider freeing the GLX pixel buffer resource in order to prevent the
system from thrashing due to insufficient resources.

For an unpreserved GLXPbuffer, a buffer clobber event, with type
@code{GLX_DAMAGED}, is generated whenever a portion of the GLX pixel
buffer becomes invalid. The client may wish to regenerate the invalid
portions of the GLX pixel buffer.

For Windows, buffer clobber events, with type @code{GLX_SAVED}, occur
whenever an ancillary buffer, associated with the window, gets clobbered
or moved out of off-screen memory. The event contains information
indicating which color buffers and ancillary buffers\(emand which
portions of those buffers\(emwere affected.

@code{GLXBadDrawable} is generated if @var{draw} is not a valid window
or a valid GLX pixel buffer.

@end deftypefun

@deftypefun void glXSwapBuffers dpy drawable
Exchange front and back buffers.

@table @asis
@item @var{dpy}
Specifies the connection to the X server.

@item @var{drawable}
Specifies the drawable whose buffers are to be swapped.

@end table

@code{glXSwapBuffers} promotes the contents of the back buffer of
@var{drawable} to become the contents of the front buffer of
@var{drawable}. The contents of the back buffer then become undefined.
The update typically takes place during the vertical retrace of the
monitor, rather than immediately after @code{glXSwapBuffers} is called.

@code{glXSwapBuffers} performs an implicit @code{glFlush} before it
returns. Subsequent OpenGL commands may be issued immediately after
calling @code{glXSwapBuffers}, but are not executed until the buffer
exchange is completed.

If @var{drawable} was not created with respect to a double-buffered
visual, @code{glXSwapBuffers} has no effect, and no error is generated.

@code{GLXBadDrawable} is generated if @var{drawable} is not a valid GLX
drawable.

@code{GLXBadCurrentWindow} is generated if @var{dpy} and @var{drawable}
are respectively the display and drawable associated with the current
context of the calling thread, and @var{drawable} identifies a window
that is no longer valid.

@end deftypefun

@deftypefun void glXUseXFont font first count listBase
Create bitmap display lists from an X font.

@table @asis
@item @var{font}
Specifies the font from which character glyphs are to be taken.

@item @var{first}
Specifies the index of the first glyph to be taken.

@item @var{count}
Specifies the number of glyphs to be taken.

@item @var{listBase}
Specifies the index of the first display list to be generated.

@end table

@code{glXUseXFont} generates @var{count} display lists, named
@var{listBase} through @r{@var{listBase}+@var{count}-1}, each containing
a single @code{glBitmap} command. The parameters of the @code{glBitmap}
command of display list @r{@var{listBase}+@var{i}} are derived from
glyph @r{@var{first}+@var{i}}. Bitmap parameters @r{@var{xorig}},
@r{@var{yorig}}, @r{@var{width}}, and @r{@var{height}} are computed from
font metrics as @r{@var{descent}-1}, @r{-@var{lbearing}},
@r{@var{rbearing}-@var{lbearing}}, and @r{@var{ascent}+@var{descent}},
respectively. @r{@var{xmove}} is taken from the glyph's @r{@var{width}}
metric, and @r{@var{ymove}} is set to zero. Finally, the glyph's image
is converted to the appropriate format for @code{glBitmap}.

Using @code{glXUseXFont} may be more efficient than accessing the X font
and generating the display lists explicitly, both because the display
lists are created on the server without requiring a round trip of the
glyph data, and because the server may choose to delay the creation of
each bitmap until it is accessed.

Empty display lists are created for all glyphs that are requested and
are not defined in @var{font}. @code{glXUseXFont} is ignored if there is
no current GLX context.

@code{BadFont} is generated if @var{font} is not a valid font.

@code{GLXBadContextState} is generated if the current GLX context is in
display-list construction mode.

@code{GLXBadCurrentWindow} is generated if the drawable associated with
the current context of the calling thread is a window, and that window
is no longer valid.

@end deftypefun

@deftypefun void glXWaitGL 
Complete GL execution prior to subsequent X calls.

GL rendering calls made prior to @code{glXWaitGL} are guaranteed to be
executed before X rendering calls made after @code{glXWaitGL}. Although
this same result can be achieved using @code{glFinish}, @code{glXWaitGL}
does not require a round trip to the server, and it is therefore more
efficient in cases where client and server are on separate machines.

@code{glXWaitGL} is ignored if there is no current GLX context.

@code{GLXBadCurrentWindow} is generated if the drawable associated with
the current context of the calling thread is a window, and that window
is no longer valid.

@end deftypefun

@deftypefun void glXWaitX 
Complete X execution prior to subsequent GL calls.

X rendering calls made prior to @code{glXWaitX} are guaranteed to be
executed before GL rendering calls made after @code{glXWaitX}. Although
the same result can be achieved using @code{XSync}, @code{glXWaitX} does
not require a round trip to the server, and it is therefore more
efficient in cases where client and server are on separate machines.

@code{glXWaitX} is ignored if there is no current GLX context.

@code{GLXBadCurrentWindow} is generated if the drawable associated with
the current context of the calling thread is a window, and that window
is no longer valid.

@end deftypefun


@c %end of fragment