GLXGETCONFIG()GLXGETCONFIG()NAMEglXGetConfig - return information about GLX visuals
C SPECIFICATION
int glXGetConfig( Display *dpy,
XVisualInfo *vis,
int attrib,
int *value )
PARAMETERS
dpy Specifies the connection to the X server.
vis Specifies the visual to be queried. It is a
pointer to an XVisualInfo structure, not a visual
ID or a pointer to a Visual.
attrib Specifies the visual attribute to be returned.
value Returns the requested value.
DESCRIPTIONglXGetConfig sets value to the attrib value of windows or
GLX pixmaps created with respect to vis. glXGetConfig
returns an error code if it fails for any reason. Other-
wise, zero is returned.
attrib is one of the following:
GLX_USE_GL True if OpenGL rendering is sup-
ported by this visual, False other-
wise.
GLX_BUFFER_SIZE Number of bits per color buffer.
For RGBA visuals, GLX_BUFFER_SIZE is
the sum of GLX_RED_SIZE,
GLX_GREEN_SIZE, GLX_BLUE_SIZE, and
GLX_ALPHA_SIZE. For color index
visuals, GLX_BUFFER_SIZE is the size
of the color indexes.
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.
GLX_RGBA True if color buffers store red,
green, blue, and alpha values.
False if they store color indexes.
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GLXGETCONFIG()GLXGETCONFIG()
GLX_DOUBLEBUFFER True if color buffers exist in
front/back pairs that can be
swapped, False otherwise.
GLX_STEREO True if color buffers exist in
left/right pairs, False otherwise.
GLX_AUX_BUFFERS Number of auxiliary color buffers
that are available. Zero indicates
that no auxiliary color buffers
exist.
GLX_RED_SIZE Number of bits of red stored in each
color buffer. Undefined if GLX_RGBA
is False.
GLX_GREEN_SIZE Number of bits of green stored in
each color buffer. Undefined if
GLX_RGBA is False.
GLX_BLUE_SIZE Number of bits of blue stored in
each color buffer. Undefined if
GLX_RGBA is False.
GLX_ALPHA_SIZE Number of bits of alpha stored in
each color buffer. Undefined if
GLX_RGBA is False.
GLX_DEPTH_SIZE Number of bits in the depth buffer.
GLX_STENCIL_SIZE Number of bits in the stencil
buffer.
GLX_ACCUM_RED_SIZE Number of bits of red stored in the
accumulation buffer.
GLX_ACCUM_GREEN_SIZE Number of bits of green stored in
the accumulation buffer.
GLX_ACCUM_BLUE_SIZE Number of bits of blue stored in the
accumulation buffer.
GLX_ACCUM_ALPHA_SIZE Number of bits of alpha stored in
the accumulation buffer.
The X protocol allows a single visual ID to be instanti-
ated 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
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
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GLXGETCONFIG()GLXGETCONFIG()
stencil buffer of at least 1 bit, a depth buffer of at
least 12 bits, and an accumulation buffer. Alpha bit-
planes are optional in this visual. However, its color
buffer size must be as great as that of the deepest True-
Color, DirectColor, PseudoColor, or StaticColor visual
supported on level zero, and it must itself be made avail-
able on level zero.
In addition, if the X server exports a PseudoColor or
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 Pseudo-
Color or 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.
NOTES
XVisualInfo is defined in Xutil.h. It is a structure that
includes visual, visualID, screen, and depth elements.
ERRORS
GLX_NO_EXTENSION is returned if dpy does not support the
GLX extension.
GLX_BAD_SCREEN is returned if the screen of vis does not
correspond to a screen.
GLX_BAD_ATTRIBUTE is returned if attrib is not a valid GLX
attribute.
GLX_BAD_VISUAL is returned if vis doesn't support GLX and
an attribute other than GLX_USE_GL is requested.
SEE ALSO
glXChooseVisual, glXCreateContext
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