XdbeGetVisualInfo(3X11) X FUNCTIONS XdbeGetVisualInfo(3X11)NAMEXdbeGetVisualInfoSYNOPSIS
#include <X11/extensions/Xdbe.h>
XdbeScreenVisualInfo *XdbeGetVisualInfo(
Display *dpy,
Drawable *screen_specifiers,
int *num_screens)
DESCRIPTION
This function returns information about which visuals sup-
port double buffering. The argument num_screens specifies
how many elements there are in the screen_specifiers list.
Each drawable in screen_specifiers designates a screen for
which the supported visuals are being requested. If
num_screens is zero, information for all screens is
requested. In this case, upon return from this function,
num_screens will be set to the number of screens that were
found. If an error occurs, this function returns NULL,
else it returns a pointer to a list of XdbeScreenVisual-
Info structures of length num_screens. The nth element in
the returned list corresponds to the nth drawable in the
screen_specifiers list, unless num_screens was passed in
with the value zero, in which case the nth element in the
returned list corresponds to the nth screen of the server,
starting with screen zero. The XdbeScreenVisualInfo
structure has the following fields:
int count
XdbeVisualInfo *visinfo
count specifies the number of items in visinfo. visinfo
specifies a list of visuals, depths, and performance hints
for this screen.
The XdbeVisualInfo structure has the following fields:
VisualID visual
int depth
int perflevel
visual specifies one visual ID that supports double-
buffering. depth specifies the depth of the visual. per-
flevel is a performance hint.
The only operation defined on a perflevel is comparison to
a perflevel of another visual on the same screen. The
visual having the higher perflevel is likely to have bet-
ter double-buffering graphics performance than the visual
having the lower perflevel. Nothing can be deduced from
the following: the magnitude of the difference of two per-
flevels, a perflevel value in isolation, or comparing
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XdbeGetVisualInfo(3X11) X FUNCTIONS XdbeGetVisualInfo(3X11)
perflevels from different servers.
ERRORS
BadDrawable
One or more values passed in screen_specifiers is
not a valid drawable.
SEE ALSO
DBE, XdbeAllocateBackBufferName(), XdbeBeginIdiom(), Xdbe-
DeallocateBackBufferName(), XdbeEndIdiom(), XdbeFreeVisu-
alInfo(), XdbeGetBackBufferAttributes(), XdbeQueryExten-
sion(), XdbeSwapBuffers().
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