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XdbeGetVisualInfo
#include <X11/extensions/Xdbe.h>
XdbeScreenVisualInfo *XdbeGetVisualInfo( Display *dpy,
Drawable *screen_specifiers,
int *num_screens)
This function returns information about which visuals support
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 XdbeScreenVisualInfo 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. perflevel 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
better 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 perflevels, a perflevel value in isolation, or
comparing perflevels from different servers.
- BadDrawable
- One or more
values passed in screen_specifiers is not a valid drawable.
DBE,
XdbeAllocateBackBufferName(), XdbeBeginIdiom(), XdbeDeallocateBackBufferName(),
XdbeEndIdiom(), XdbeFreeVisualInfo(), XdbeGetBackBufferAttributes(), XdbeQueryExtension(),
XdbeSwapBuffers().
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