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XdbeGetVisualInfo(3)			   X FUNCTIONS			     XdbeGetVisualInfo(3)

NAME
       XdbeGetVisualInfo - Get dbe Visual Informations

SYNOPSIS
       #include <X11/extensions/Xdbe.h>

       XdbeScreenVisualInfo *XdbeGetVisualInfo(
	   Display  *dpy,
	   Drawable *screen_specifiers,
	   int	    *num_screens)

DESCRIPTION
       This function returns information about which visuals support double buffering.	The argu-
       ment 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  dou-
       ble-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.

ERRORS
       BadDrawable
	      One or more values passed in screen_specifiers is not a valid drawable.

SEE ALSO
       DBE,   XdbeAllocateBackBufferName(),   XdbeBeginIdiom(),   XdbeDeallocateBackBufferName(),
       XdbeEndIdiom(), XdbeFreeVisualInfo(), XdbeGetBackBufferAttributes(), XdbeQueryExtension(),
       XdbeSwapBuffers().

X Version 11				  libXext 1.3.2 		     XdbeGetVisualInfo(3)
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