NAME
glXGetConfig
- return information about GLX visuals
C SPECIFICATION
int ggllXXGGeettCCoonnffiigg(
Display _*_d_p_y,
XVisualInfo _*_v_i_s,
int _a_t_t_r_i_b,
int _*_v_a_l_u_e )
delim $$
PARAMETERS
-
_d_p_y
-
Specifies the connection to the X server.
-
_v_i_s
-
Specifies the visual to be queried.
It is a pointer to an XXVViissuuaallIInnffoo structure,
not a visual ID or a pointer to a VViissuuaall.
-
_a_t_t_r_i_b
-
Specifies the visual attribute to be returned.
-
_v_a_l_u_e
-
Returns the requested value.
DESCRIPTION
ggllXXGGeettCCoonnffiigg sets _v_a_l_u_e to the _a_t_t_r_i_b value of windows or GLX pixmaps
created with respect to _v_i_s.
ggllXXGGeettCCoonnffiigg returns an error code if it fails for any reason.
Otherwise, zero is returned.
_a_t_t_r_i_b is one of the following:
-
GGLLXX__UUSSEE__GGLL
-
TTrruuee if OpenGL rendering is supported by this visual,
FFaallssee otherwise.
-
GGLLXX__BBUUFFFFEERR__SSIIZZEE
-
Number of bits per color buffer.
For RGBA visuals, GGLLXX__BBUUFFFFEERR__SSIIZZEE is the sum of
GGLLXX__RREEDD__SSIIZZEE,
GGLLXX__GGRREEEENN__SSIIZZEE,
GGLLXX__BBLLUUEE__SSIIZZEE, and
GGLLXX__AALLPPHHAA__SSIIZZEE.
For color index visuals, GGLLXX__BBUUFFFFEERR__SSIIZZEE is the size of the
color indexes.
-
GGLLXX__LLEEVVEELL
-
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.
-
GGLLXX__RRGGBBAA
-
TTrruuee if color buffers store red, green, blue, and alpha values.
FFaallssee if they store color indexes.
-
GGLLXX__DDOOUUBBLLEEBBUUFFFFEERR
-
TTrruuee if color buffers exist in front/back pairs that can be swapped,
FFaallssee otherwise.
-
GGLLXX__SSTTEERREEOO
-
TTrruuee if color buffers exist in left/right pairs,
FFaallssee otherwise.
-
GGLLXX__AAUUXX__BBUUFFFFEERRSS
-
Number of auxiliary color buffers that are available.
Zero indicates that no auxiliary color buffers exist.
-
GGLLXX__RREEDD__SSIIZZEE
-
Number of bits of red stored in each color buffer.
Undefined if GGLLXX__RRGGBBAA is FFaallssee.
-
GGLLXX__GGRREEEENN__SSIIZZEE
-
Number of bits of green stored in each color buffer.
Undefined if GGLLXX__RRGGBBAA is FFaallssee.
-
GGLLXX__BBLLUUEE__SSIIZZEE
-
Number of bits of blue stored in each color buffer.
Undefined if GGLLXX__RRGGBBAA is FFaallssee.
-
GGLLXX__AALLPPHHAA__SSIIZZEE
-
Number of bits of alpha stored in each color buffer.
Undefined if GGLLXX__RRGGBBAA is FFaallssee.
-
GGLLXX__DDEEPPTTHH__SSIIZZEE
-
Number of bits in the depth buffer.
-
GGLLXX__SSTTEENNCCIILL__SSIIZZEE
-
Number of bits in the stencil buffer.
-
GGLLXX__AACCCCUUMM__RREEDD__SSIIZZEE
-
Number of bits of red stored in the accumulation buffer.
-
GGLLXX__AACCCCUUMM__GGRREEEENN__SSIIZZEE
-
Number of bits of green stored in the accumulation buffer.
-
GGLLXX__AACCCCUUMM__BBLLUUEE__SSIIZZEE
-
Number of bits of blue stored in the accumulation buffer.
-
GGLLXX__AACCCCUUMM__AALLPPHHAA__SSIIZZEE
-
Number of bits of alpha stored in the accumulation buffer.
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 GGLLXX__BBUUFFFFEERR__SSIIZZEE.
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 TTrruueeCCoolloorr, DDiirreeccttCCoolloorr,
PPsseeuuddooCCoolloorr, or SSttaattiiccCCoolloorr visual supported on level zero,
and it must itself be made available on level zero.
In addition, if the X server exports a PPsseeuuddooCCoolloorr
or SSttaattiiccCCoolloorr 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
PPsseeuuddooCCoolloorr or SSttaattiiccCCoolloorr 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
XXVViissuuaallIInnffoo is defined in _X_u_t_i_l_._h_.
It is a structure that includes _v_i_s_u_a_l, _v_i_s_u_a_l_I_D, _s_c_r_e_e_n, and
_d_e_p_t_h elements.
ERRORS
GGLLXX__NNOO__EEXXTTEENNSSIIOONN is returned if _d_p_y does not support the GLX
extension.
GGLLXX__BBAADD__SSCCRREEEENN is returned if the screen of _v_i_s does not correspond
to a screen.
GGLLXX__BBAADD__AATTTTRRIIBBUUTTEE is returned if _a_t_t_r_i_b is not a valid GLX attribute.
GGLLXX__BBAADD__VVIISSUUAALL is returned if _v_i_s doesn't support GLX and an
attribute other than GGLLXX__UUSSEE__GGLL is requested.
SEE ALSO
ggllXXCChhoooosseeVViissuuaall,
ggllXXCCrreeaatteeCCoonntteexxtt