int scree )
PARAMETERS
dpy Specifies the connection to the X server.
scree Specifies the screen number.
_param3
Specifies a list of boolean attributes and integer attri‐
bute/value pairs. The last attribute must be None.
DESCRIPTION
glXChooseVisual returns a pointer to an XVisualInfo structure describing
the visual that best meets a minimum specification. The boolean GLX at‐
tributes 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 visu‐
als, respectively. If no conforming visual exists, NULL is returned.
To free the data returned by this function, use XFree.
All boolean GLX attributes default to False except GLX_USE_GL, which de‐
faults to True. All integer GLX attributes default to zero. Default
specifications are superseded by attributes included in _param3. Bool‐
ean attributes included in _param3 are understood to be True. Integer
attributes and enumerated type attributes are followed immediately by
the corresponding desired or minimum value. The list must be terminated
with None.
The interpretations of the various GLX visual attributes are as follows:
GLX_USE_GL Ignored. Only visuals that can be rendered with
GLX are considered.
GLX_BUFFER_SIZE Must be followed by a nonnegative integer that in‐
dicates the desired color index buffer size. The
smallest index buffer of at least the specified
size is preferred. Ignored if GLX_RGBA is as‐
serted.
GLX_LEVEL Must be followed by an integer buffer-level speci‐
fication. 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.
GLX_RGBA If present, only TrueColor and DirectColor visuals
are considered. Otherwise, only PseudoColor and
StaticColor visuals are considered.
specification. If this value is zero, the small‐
est available red buffer is preferred. Otherwise,
the largest available red buffer of at least the
minimum size is preferred.
GLX_GREEN_SIZE Must be followed by a nonnegative minimum size
specification. If this value is zero, the small‐
est available green buffer is preferred. Other‐
wise, the largest available green buffer of at
least the minimum size is preferred.
GLX_BLUE_SIZE Must be followed by a nonnegative minimum size
specification. If this value is zero, the small‐
est available blue buffer is preferred. Other‐
wise, the largest available blue buffer of at
least the minimum size is preferred.
GLX_ALPHA_SIZE Must be followed by a nonnegative minimum size
specification. If this value is zero, the small‐
est available alpha buffer is preferred. Other‐
wise, the largest available alpha buffer of at
least the minimum size is preferred.
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.
GLX_STENCIL_SIZE Must be followed by a nonnegative integer that in‐
dicates the desired number of stencil bitplanes.
The smallest stencil buffer of at least the speci‐
fied size is preferred. If the desired value is
zero, visuals with no stencil buffer are pre‐
ferred.
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.
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.
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
four bits each of red, green, and blue, and possibly no bits of alpha.
It does not support color index mode, double-buffering, or stereo dis‐
play. It may or may not have one or more auxiliary color buffers, a
depth buffer, a stencil buffer, or an accumulation buffer.
NOTES
XVisualInfo is defined in Xutil.h. It is a structure that includes vis‐
ual, visualID, screen, and depth elements.
glXChooseVisual is implemented as a client-side utility using only
XGetVisualInfo and glXGetConfig. Calls to these two routines can be
used to implement selection algorithms other than the generic one imple‐
mented by glXChooseVisual.
GLX implementers are strongly discouraged, but not proscribed, from
changing the selection algorithm used by glXChooseVisual. Therefore,
selections may change from release to release of the client-side li‐
brary.
There is no direct filter for picking only visuals that support GLX‐
Pixmaps. GLXPixmaps are supported for visuals whose GLX_BUFFER_SIZE is
one of the pixmap depths supported by the X server.
ERRORS
NULL is returned if an undefined GLX attribute is encountered in
_param3.
SEE ALSO
glXCreateContext, glXGetConfig
GLXCHOOSEVISUAL(3G)
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