Creates an overlay over an existing window, allowing for manipulations like rubberbanding, etc. On wxOSX the overlay is implemented with native platform APIs, on the other platforms it is simulated using wxMemoryDC.
See: wxDCOverlay, wxDC
wxWidgets docs: wxOverlay
wxOverlay() = wx:wx_object()
new() -> wxOverlay()
destroy(This :: wxOverlay()) -> ok
reset(This) -> ok
This = wxOverlay()
Clears the overlay without restoring the former state.
To be done, for example, when the window content has been changed and repainted.