glXChooseFBConfigSGIX(3G) OpenGL Reference - GLX glXChooseFBConfigSGIX(3G)
NAME
glXChooseFBConfigSGIX - return a list of GLX frame buffer configurations
that match the specified attributes
C SPECIFICATION
GLXFBConfigSGIX * glXChooseFBConfigSGIX( Display *dpy,
int screen,
int *attrib_list,
int *nitems )
PARAMETERS
dpy Specifies the connection to the X server.
screen Specifies the screen number.
attrib_list Specifies a list of attribute/value pairs. The last
attribute must be None.
nitems Returns the number of elements in the list returned by
glXChooseFBConfigSGIX.
DESCRIPTION
If attrib_list is NULL then glXChooseFBConfigSGIX returns an array of GLX
frame buffer configurations that are available on the specified screen;
otherwise glXChooseFBConfigSGIX returns an array of GLX frame buffer
configurations that match the specified attributes. If an error occurs,
no frame buffer configurations exist on the specified screen, or if no
frame buffer configurations match the specified attributes, then NULL is
returned. Use XFree to free the memory returned by
glXChooseFBConfigSGIX.
All attributes in attrib_list, including boolean attributes, are
immediately followed by the corresponding desired value. The list is
terminated with None. If an attribute is not specified in attrib_list
then the default value (see below) is used (and the attribute is said to
be specified implicitly). For example, if GLXSTEREO is not specified
then it is assumed to be False. For some attributes, the default is
"don't 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 GLXLEVEL, must match the specified value exactly;
others, such as, GLXREDSIZE 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
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order is defined below.
The interpretations of the various GLX visual attributes are as follows:
GLXBUFFERSIZE 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
GLXCOLORINDEXBITSGIX is not set in
GLXRENDERTYPESGIX. The default value is 0.
GLXLEVEL Must be followed by an integer buffer-level
specification. This specification is honored
exactly. Buffer level zero corresponds to the
default 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. The default value is 0.
GLXDOUBLEBUFFER Must be followed by True or False. If True is
specified then only double-buffered frame buffer
configurations are considered; if False is
specified then only single-buffered frame buffer
configurations are considered. The default
value is "don't care".
GLXSTEREO Must be followed by True or False. If True is
specified then only stereo frame buffer
configurations are considered; if False is
specified then only monoscopic frame buffer
configurations are considered. The default
value is False.
GLXAUXBUFFERS 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.
GLXREDSIZE 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. The
default value is 0.
GLXGREENSIZE 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
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at least the minimum size is preferred. The
default value is 0.
GLXBLUESIZE 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. The
default value is 0.
GLXALPHASIZE 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. The
default value is 0.
GLXDEPTHSIZE 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.
GLXSTENCILSIZE 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.
GLXACCUMREDSIZE 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.
GLXACCUMGREENSIZE 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.
GLXACCUMBLUESIZE 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
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possible blue accumulation buffer of at least
the minimum size is preferred. The default
value is 0.
GLXACCUMALPHASIZE 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.
GLXSAMPLEBUFFERSSGIS Must be followed by the minimum acceptable
number of multisample buffers. Configurations
with the smallest number of multisample buffers
that meet or exceed this minimum number are
preferred. Currently operation with more than
one multisample buffer is undefined, so only
values of zero or one will produce a match. The
default value is 0.
GLXSAMPLESSGIS Must be followed by the minimum number of
samples required in multisample buffers.
Configurations with the smallest number of
samples that meet or exceed the specified
minimum number are preferred. Note that it is
possible for color samples in the multisample
buffer to have fewer bits than colors in the
main color buffers. However, multisampled
colors maintain at least as much color
resolution in aggregate as the main color
buffers.
The default value is 0.
GLXTRANSPARENTTYPEEXT Must be followed by one of GLXNONEEXT,
GLXTRANSPARENTRGBEXT,
GLXTRANSPARENTINDEXEXT. If GLXNONEEXT is
specified, then only opaque frame buffer
configurations will be considered; if
GLXTRANSPARENTRGBEXT is specified, then only
transparent frame buffer configurations that
support RGBA rendering will be considered; if
GLXTRANSPARENTINDEXEXT is specified, then
only transparent frame buffer configurations
that support color index rendering will be
considered. The default value is GLXNONEEXT.
GLXTRANSPARENTINDEXVALUEEXT
Must be followed by an integer value indicating
the transparent index value; the value must be
between 0 and the maximum framebuffer value for
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indices. Only frame buffer configurations that
use the specified transparent index value will
be considered. The default value is "don't
care".
This attribute is ignored unless
GLXTRANSPARENTTYPEEXT is included in
attrib_list and specified as
GLXTRANSPARENTINDEXEXT.
GLXTRANSPARENTREDVALUEEXT
Must be followed by an integer value indicating
the transparent red value; the value must be
between 0 and the maximum framebuffer value for
red. Only frame buffer configurations that use
the specified transparent red value will be
considered. The default value is "don't care".
This attribute is ignored unless
GLXTRANSPARENTTYPEEXT is included in
attrib_list and specified as
GLXTRANSPARENTRGBEXT.
GLXTRANSPARENTGREENVALUEEXT
Must be followed by an integer value indicating
the transparent green value; the value must be
between 0 and the maximum framebuffer value for
green. Only frame buffer configurations that
use the specified transparent green value will
be considered. The default value is "don't
care".
This attribute is ignored unless
GLXTRANSPARENTTYPEEXT is included in
attrib_list and specified as
GLXTRANSPARENTRGBEXT.
GLXTRANSPARENTBLUEVALUEEXT
Must be followed by an integer value indicating
the transparent blue value; the value must be
between 0 and the maximum framebuffer value for
blue. Only frame buffer configurations that use
the specified transparent blue value will be
considered. The default value is "don't care".
This attribute is ignored unless
GLXTRANSPARENTTYPEEXT is included in
attrib_list and specified as
GLXTRANSPARENTRGBEXT.
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GLXTRANSPARENTALPHAVALUEEXT
Must be followed by an integer value. This
attribute is always ignored; it is for future
use only.
GLXVISUALCAVEATEXT Must be followed by one of GLXNONEEXT,
GLXSLOWVISUALEXT, GLXNONCONFORMANTEXT. If
GLXNONEEXT is specified, then only frame
buffer configurations with no caveats will be
considered; if GLXSLOWVISUALEXT, is specified
then only slow frame buffer configurations will
be considered; if GLXNONCONFORMANTEXT is
specified then only non-conformant frame buffer
configurations will be considered. The default
value is "don't care".
GLXDRAWABLETYPESGIX Must be followed by a mask indicating which GLX
drawable types the frame buffer configuration
must support. Valid bits are
GLXWINDOWBITSGIX, GLXPIXMAPBITSGIX and
GLXPBUFFERBITSGIX. For example, if mask is
set to GLXWINDOWBITSGIX |
GLXPIXMAPBITSGIX, only frame buffer
configurations that support both windows and GLX
pixmaps will be considered. The default value
is GLXWINDOWBITSGIX.
GLXRENDERTYPESGIX Must be followed by a mask indicating which
OpenGL rendering modes the frame buffer
configuration must support. Valid bits are
GLXRGBABITSGIX and GLXCOLORINDEXBITSGIX.
If the mask is set to GLXRGBABITSGIX |
GLXCOLORINDEXBITSGIX then only frame buffer
configurations that can be bound to both RGBA
contexts and color index contexts will be
considered. The default value is
GLXRGBABITSGIX.
GLXXVISUALTYPEEXT Must be followed by one of GLXTRUECOLOREXT,
GLXDIRECTCOLOREXT, GLXPSEUDOCOLOREXT,
GLXSTATICCOLOREXT, GLXGRAYSCALEEXT,
GLXSTATICGRAYEXT, indicating the desired X
visual type. Not all frame buffer
configurations have an associated X visual. If
GLXDRAWABLETYPESGIX is specified in
attrib_list and the mask that follows does not
have GLXWINDOWBITSGIX set, then this value is
ignored. It is also ignored if
GLXXRENDERABLESGIX is specified as False.
RGBA rendering may be supported for visuals of
type GLXTRUECOLOREXT, GLXDIRECTCOLOREXT,
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GLXPSEUDOCOLOREXT, or GLXSTATICCOLOREXT,
but color index rendering is only supported for
visuals of type GLXPSEUDOCOLOREXT or
GLXSTATICCOLOREXT (i.e., single-channel
visuals).
The tokens GLXGRAYSCALEEXT and
GLXSTATICGRAYEXT will not match current
OpenGL enabled visuals, but are included for
future use.
The default value for GLXXVISUALTYPEEXT is
"don't care".
GLXXRENDERABLESGIX Must be followed by True or False. If 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 "don't care".
GLXFBCONFIGIDSGIX Must be followed by an XID for a GLXFBConfig.
When GLXFBCONFIGIDSGIX is specified in
attrib_list, all other attributes are ignored,
and only the frame buffer configuration with the
given XID is returned. NULL is returned if the
frame buffer configuration does not exist. The
default value for GLXFBCONFIGIDSGIX is "don't
care".
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 that are applied in
ascending order (i.e., configurations that are considered equal by lower
numbered rule are sorted by the higher numbered rule):
1. by GLX_VISUAL_RATING_EXT where the precedence is GLX_NONE_EXT,
GLX_NON_CONFORMANT, GLX_SLOW_VISUAL.
2. larger total number of RGBA color components (GLX_RED_BITS,
GLX_GREEN_BITS, GLX_BLUE_BITS, and GLX_ALPHA_BITS) that have higher
number of bits,
3. smaller GLX_INDEX_BITS,
4. single buffered configuration (GLX_DOUBLE_BUFFER being False)
precedes a double buffered one,
5. smaller GLX_AUX_BUFFERS,
6. smaller GLX_SAMPLE_BUFFERS_SGIS,
7. smaller GLX_SAMPLES_SGIS,
8. larger GLX_DEPTH_BITS,
9. smaller GLX_STENCIL_BITS,
10. larger total number of accumulation buffer color components
(GLX_ACCUM_RED_BITS, GLX_ACCUM_GREEN_BITS, GLX_ACCUM_BLUE_BITS, and
GLX_ACCUM_ALPHA_BITS) that have higher number of bits;
11. sort by GLX_VISUAL_TYPE_EXT where the precedence order is
GLX_TRUE_COLOR_EXT, GLX_DIRECT_COLOR_EXT, GLX_PSEUDO_COLOR_EXT,
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GLX_STATIC_COLOR_EXT, GLX_GRAY_SCALE_EXT, GLX_STATIC_GRAY_EXT,
EXAMPLES
attrib_list =
{GLXRENDERTYPESGIX, GLXRGBABITSGIX, GLXREDSIZE, 4,
GLXGREENSIZE, 4, GLXBLUESIZE, 4, None};
Specifies a frame buffer configuration that supports RGBA rendering and
exists in the normal frame buffer, not an overlay or underlay buffer.
The returned visual supports at least four bits each of red, green, and
blue, and possibly no bits of alpha. It does not support stereo display.
It may or may not have one or more auxiliary color buffers, a back
buffer, a depth buffer, a stencil buffer, or an accumulation buffer.
NOTES
glXChooseFBConfigSGIX is part of the GLXSGIXfbconfig extension.
glXChooseFBConfigSGIX is implemented as a client-side utility; it does
not require a round-trip to the X server.
glXChooseFBConfigSGIX and glXGetFBConfigAttribSGIX can be used to
implement selection algorithms other than the generic one implemented by
glXChooseFBConfigSGIX. Call glXChooseFBConfigSGIX to retrieve all the
frame buffer configurations on a particular screen or, alternatively, all
the frame buffer configurations with a particular set of attributes. Next
call glXGetFBConfigAttribSGIX to retrieve additional attributes for the
frame buffer configurations and then select between them.
GLX implementers are strongly discouraged, but not proscribed, from
changing the selection algorithm used by glXChooseFBConfigSGIX.
Therefore, selections may change from release to release of the client-
side library.
GLXSAMPLEBUFFERSSGIS and GLXSAMPLESSGIS are not valid attributes
unless the SGISmultisample extension is supported.
GLXXVISUALTYPEEXT, GLXTRANSPARENTTYPEEXT,
GLXTRANSPARENTINDEXVALUEEXT, GLXTRANSPARENTREDVALUEEXT,
GLXTRANSPARENTGREENVALUEEXT, GLXTRANSPARENTBLUEVALUEEXT, and
GLXTRANSPARENTALPHAVALUEEXT are not valid attributes unless the
EXTvisualinfo extension is supported.
GLXVISUALCAVEATEXT is not a valid attribute unless the
EXTvisualrating extension is supported.
ERRORS
NULL is returned if an undefined GLX attribute is encountered in
attrib_list, if screen is invalid or if dpy does not support the GLX
extension.
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MACHINE DEPENDENCIES
The SGISmultisample extension is supported only on RealityEngine,
RealityEngine2, and VTX systems and InfiniteReality systems.
SEE ALSO
glXGetFBConfigAttribSGIX, glXCreateContextWithConfigSGIX,
glXCreateGLXPixmapWithConfigSGIX, glXGetVisualFromFBConfigSGIX.
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