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
       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.

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().