VCancelEvents - frees all the events except Expose events in all the
VCancelEvents frees all the events in the image window, dialog window,
and button window (except Expose event) to prevent more than one client
from selecting SubstructureRedirectMask, ResizeRedirectMask, or
ButtonPressMask on the same window. VCancelEvents should be called before
calling a process or returning if this process shares windows with another
0 - work successfully.
VCreateWindows must be called first.