Retrieves a pixel from @window to force the windowing system to carry out any pending rendering commands.
This function is intended to be used in GTK+ test programs. It will warp the mouse pointer to the given (@x,@y) coordinates within @window and simulate a button press or release event. Because the mouse pointer needs to be warped to the target location, use of this function outside of test programs that run in their own virtual windowing system (e.g. Xvfb) is not recommended.
This function is intended to be used in GTK+ test programs. If (@x,@y) are > (-1,-1), it will warp the mouse pointer to the given (@x,@y) coordinates within @window and simulate a key press or release event.