glXChooseFBConfig man page on RedHat
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GLXCHOOSEFBCONFIG(3G) OpenGL Manual GLXCHOOSEFBCONFIG(3G)
NAME
glXChooseFBConfig - return a list of GLX frame buffer configurations
that match the specified attributes
C SPECIFICATION
GLXFBConfig * glXChooseFBConfig(Display * dpy, int screen,
const int * attrib_list,
int * nelements);
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.
nelements
Returns the number of elements in the list returned by
glXChooseFBConfig.
DESCRIPTION
glXChooseFBConfig returns GLX frame buffer configurations that match
the attributes specified in attrib_list, or NULL if no matches are
found. If attrib_list is NULL, then 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 NULL is returned. Use XFree to free the
memory returned by glXChooseFBConfig.
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 GLX_STEREO is not
specified, then it is assumed to be False. For some attributes, the
default is 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 GLX_LEVEL, must match the specified value exactly;
others, such as, 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:
GLX_FBCONFIG_ID
Must be followed by a valid XID that indicates the desired GLX
frame buffer configuration. When a GLX_FBCONFIG_ID is specified,
all attributes are ignored. The default value is GLX_DONT_CARE.
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
GLX_COLOR_INDEX_BIT is not set in GLX_RENDER_TYPE. The default
value is 0.
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.
GLX_DOUBLEBUFFER
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 GLX_DONT_CARE.
GLX_STEREO
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.
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.
GLX_RED_SIZE, GLX_GREEN_SIZE, GLX_BLUE_SIZE, GLX_ALPHA_SIZE
Each attribute, if present, must be followed by a nonnegative
minimum size specification or GLX_DONT_CARE. The largest available
total RGBA color buffer size (sum of GLX_RED_SIZE, GLX_GREEN_SIZE,
GLX_BLUE_SIZE, and 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 GLX_DONT_CARE, it is
not considered. The default value for each color component is 0.
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.
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.
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.
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.
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.
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.
GLX_RENDER_TYPE
Must be followed by a mask indicating which OpenGL rendering modes
the frame buffer configuration must support. Valid bits are
GLX_RGBA_BIT and GLX_COLOR_INDEX_BIT. If the mask is set to
GLX_RGBA_BIT | 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
GLX_RGBA_BIT.
GLX_DRAWABLE_TYPE
Must be followed by a mask indicating which GLX drawable types the
frame buffer configuration must support. Valid bits are
GLX_WINDOW_BIT, GLX_PIXMAP_BIT, and GLX_PBUFFER_BIT. For example,
if mask is set to GLX_WINDOW_BIT | GLX_PIXMAP_BIT, only frame
buffer configurations that support both windows and GLX pixmaps
will be considered. The default value is GLX_WINDOW_BIT.
GLX_X_RENDERABLE
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 GLX_DONT_CARE.
GLX_X_VISUAL_TYPE
Must be followed by one of GLX_TRUE_COLOR, GLX_DIRECT_COLOR,
GLX_PSEUDO_COLOR, GLX_STATIC_COLOR, GLX_GRAY_SCALE, or
GLX_STATIC_GRAY, indicating the desired X visual type. Not all
frame buffer configurations have an associated X visual. If
GLX_DRAWABLE_TYPE is specified in attrib_list and the mask that
follows does not have GLX_WINDOW_BIT set, then this value is
ignored. It is also ignored if GLX_X_RENDERABLE is specified as
False. RGBA rendering may be supported for visuals of type
GLX_TRUE_COLOR, GLX_DIRECT_COLOR, GLX_PSEUDO_COLOR, or
GLX_STATIC_COLOR, but color index rendering is only supported for
visuals of type GLX_PSEUDO_COLOR or GLX_STATIC_COLOR (i.e.,
single-channel visuals). The tokens GLX_GRAY_SCALE and
GLX_STATIC_GRAY will not match current OpenGL enabled visuals, but
are included for future use. The default value for
GLX_X_VISUAL_TYPE is GLX_DONT_CARE.
GLX_CONFIG_CAVEAT
Must be followed by one of GLX_NONE, GLX_SLOW_CONFIG,
GLX_NON_CONFORMANT_CONFIG. If GLX_NONE is specified, then only
frame buffer configurations with no caveats will be considered; if
GLX_SLOW_CONFIG is specified, then only slow frame buffer
configurations will be considered; if GLX_NON_CONFORMANT_CONFIG is
specified, then only nonconformant frame buffer configurations will
be considered. The default value is GLX_DONT_CARE.
GLX_TRANSPARENT_TYPE
Must be followed by one of GLX_NONE, GLX_TRANSPARENT_RGB,
GLX_TRANSPARENT_INDEX. If GLX_NONE is specified, then only opaque
frame buffer configurations will be considered; if
GLX_TRANSPARENT_RGB is specified, then only transparent frame
buffer configurations that support RGBA rendering will be
considered; if GLX_TRANSPARENT_INDEX is specified, then only
transparent frame buffer configurations that support color index
rendering will be considered. The default value is GLX_NONE.
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 GLX_DONT_CARE. This attribute is ignored unless
GLX_TRANSPARENT_TYPE is included in attrib_list and specified as
GLX_TRANSPARENT_INDEX.
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 GLX_DONT_CARE. This attribute is ignored unless
GLX_TRANSPARENT_TYPE is included in attrib_list and specified as
GLX_TRANSPARENT_RGB.
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 GLX_DONT_CARE. This attribute is ignored unless
GLX_TRANSPARENT_TYPE is included in attrib_list and specified as
GLX_TRANSPARENT_RGB.
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 GLX_DONT_CARE. This attribute is ignored unless
GLX_TRANSPARENT_TYPE is included in attrib_list and specified as
GLX_TRANSPARENT_RGB.
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 GLX_DONT_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, 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):
1.
By GLX_CONFIG_CAVEAT where the precedence is GLX_NONE,
GLX_SLOW_CONFIG, and GLX_NON_CONFORMANT_CONFIG.
2.
Larger total number of RGBA color components (GLX_RED_SIZE,
GLX_GREEN_SIZE, GLX_BLUE_SIZE, plus GLX_ALPHA_SIZE) that have
higher number of bits. If the requested number of bits in
attrib_list is zero or GLX_DONT_CARE for a particular color
component, then the number of bits for that component is not
considered.
3.
Smaller GLX_BUFFER_SIZE.
4.
Single buffered configuration (GLX_DOUBLEBUFFER being False
precedes a double buffered one.
5.
Smaller GLX_AUX_BUFFERS.
6.
Larger GLX_DEPTH_SIZE.
7.
Smaller GLX_STENCIL_SIZE.
8.
Larger total number of accumulation buffer color components
(GLX_ACCUM_RED_SIZE, GLX_ACCUM_GREEN_SIZE, GLX_ACCUM_BLUE_SIZE,
plus GLX_ACCUM_ALPHA_SIZE) that have higher number of bits. If the
requested number of bits in attrib_list is zero or GLX_DONT_CARE
for a particular color component, then the number of bits for that
component is not considered.
9.
By GLX_X_VISUAL_TYPE where the precedence order is GLX_TRUE_COLOR,
GLX_DIRECT_COLOR, GLX_PSEUDO_COLOR, GLX_STATIC_COLOR,
GLX_GRAY_SCALE, GLX_STATIC_GRAY.
EXAMPLES
attrib_list =
{GLX_RENDER_TYPE, GLX_RGBA_BIT, GLX_RED_SIZE, 4, GLX_GREEN_SIZE, 4,
GLX_BLUE_SIZE, 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
glXChooseFBConfig is available only if the GLX version is 1.3 or
greater.
If the GLX version is 1.1 or 1.0, the GL version must be 1.0. If the
GLX version is 1.2, then the GL version must be 1.1. If the GLX version
is 1.3, then the GL version must be 1.2.
glXGetFBConfigs() and glXGetFBConfigAttrib() can be used to implement
selection algorithms other than the generic one implemented by
glXChooseFBConfig. Call glXChooseFBConfig 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 glXGetFBConfigAttrib() to retrieve additional attributes for the
frame buffer configurations and then select between them.
GLX implementations are strongly discouraged, but not proscribed, from
changing the selection algorithm used by glXChooseFBConfig. Therefore,
selections may change from release to release of the client-side
library.
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.
SEE ALSO
glXGetFBConfigAttrib(), glXGetFBConfigs(), glXGetVisualFromFBConfig()
COPYRIGHT
Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed
under the SGI Free Software B License. For details, see
http://oss.sgi.com/projects/FreeB/.
AUTHORS
opengl.org
opengl.org 03/16/2013 GLXCHOOSEFBCONFIG(3G)
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