glXGetConfig: return information about GLX visuals.
C Specification |
glXGetConfig 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. Otherwise, zero is returned.
- Specifies the connection to the X server.
- Specifies the visual to be queried. It is a pointer to an
XVisualInfo structure, not a visual ID or a pointer to a
- Specifies the visual attribute to be returned.
- Returns the requested value.
attrib is one of the following:
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
- True if OpenGL rendering is supported by this visual,
- Number of bits per color buffer. For RGBA visuals,
GLX_BUFFER_SIZE is the sum of
GLX_BLUE_SIZE, and GLX_ALPHA_SIZE. For
color index visuals, GLX_BUFFER_SIZE is the size of the
- 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
- True if color buffers store red, green, blue, and alpha values.
False if they store color indexes.
- True if color buffers exist in front/back pairs that can be
swapped, False otherwise.
- True if color buffers exist in left/right pairs, False
- Number of auxiliary color buffers that are available. Zero indicates that
no auxiliary color buffers exist.
- Number of bits of red stored in each color buffer. Undefined if
- Number of bits of green stored in each color buffer. Undefined if
- Number of bits of blue stored in each color buffer. Undefined if
- Number of bits of alpha stored in each color buffer. Undefined if
- Number of bits in the depth buffer.
- Number of bits in the stencil buffer.
- Number of bits of red stored in the accumulation buffer.
- Number of bits of green stored in the accumulation buffer.
- Number of bits of blue stored in the accumulation buffer.
- Number of bits of alpha stored in the accumulation buffer.
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 TrueColor, DirectColor, PseudoColor, or StaticColor visual supported
on level zero, and it must itself be made available 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 PseudoColor or StaticColor visual supported on level
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
XVisualInfo is defined in Xutil.h. It is a structure that
includes visual, visualID,
screen, and depth elements.
- 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