XDoes*() XDoes*()
Name
XDoesBackingStore, XDoesSaveUnders, DoesBackingStore, DoesSaveUnders - query server support for backing store or save unders.
Synopsis
int XDoesBackingStore(screen)
Screen *screen;
Bool XDoesSaveUnders(screen)
Screen *screen;
Arguments
screen Specifies the appropriate Screen structure.
Returns
XDoesSaveUnders() returns True or False. XDoesBackingStore() returns WhenMapped, NotUseful, or Always.
Description
XDoesSaveUnders() returns a boolean value indicating whether the screen supports save unders. If True, the screen supports save unders.
If False, the screen does not support save unders.
XDoesBackingStore() returns a value indicating whether the screen supports backing stores. The value returned can be one of WhenMapped,
NotUseful, or Always.
Save unders and backing stores are optional server features controlled with window attributes. These macros tell you whether the server
supports them. A "save under" is an area beneath a window (usually a menu or dialog box) that the server saves, so that when the window is
removed from the screen, the underlying applications do not need to redraw their windows. This speeds up user response with a slight cost
in increased server memory consumption. A "backing store" is an off-screen copy of a window, maintained even when the window is not visi-
ble or not mapped. The server uses the copy to redraw the window whenever that window would otherwise have received an Expose event. This
reduces the load on applications at the expense of a possibly great increase in server memory usage.
The C language macros DoesSaveUnders() and DoesBackingStore() are equivalent and slightly more efficient.
See Also
XChangeWindowAttributes(), XGetWindowAttributes().
Xlib - Macro Equivalents XDoes*()
