region.
A backing store (offscreen buffer) large enough to contain region
will be created. The backing store will be initialized with the
background color or background pixmap for window. Then, all
drawing operations performed on window will be diverted to the
backing store. When you call gdkWindowEndPaint, the backing
store will be copied to window, making it visible onscreen. Only
the part of window contained in region will be modified; that is,
drawing operations are clipped to region.gdkWindowBeginPaintRegion(object, region)objectregiongdkWindowEndPaint. If you draw to window directly without
calling gdkWindowBeginPaintRegion, the user may see flicker
as individual drawing operations are performed in sequence. The
clipping and background-initializing features of
gdkWindowBeginPaintRegion are conveniences for the
programmer, so you can avoid doing that work yourself.
When using GTK+, the widget system automatically places calls to
gdkWindowBeginPaintRegion and gdkWindowEndPaint around
emissions of the expose_event signal. That is, if you're writing an
expose event handler, you can assume that the exposed area in
GdkEventExpose has already been cleared to the window background,
is already set as the clip region, and already has a backing store.
Therefore in most cases, application code need not call
gdkWindowBeginPaintRegion. (You can disable the automatic
calls around expose events on a widget-by-widget basis by calling
gtkWidgetSetDoubleBuffered.)
If you call this function multiple times before calling the
matching gdkWindowEndPaint, the backing stores are pushed onto
a stack. gdkWindowEndPaint copies the topmost backing store
onscreen, subtracts the topmost region from all other regions in
the stack, and pops the stack. All drawing operations affect only
the topmost backing store in the stack. One matching call to
gdkWindowEndPaint is required for each call to
gdkWindowBeginPaintRegion.