Prevents drawing within invalid areas of a window by excluding an updated region in the window from the clipping region associated with the CDC object.
Points to the window object whose window is being updated.
The type of excluded region. It can be any one of the following values:
COMPLEXREGION The region has overlapping borders.
ERROR No region was created.
NULLREGION The region is empty.
SIMPLEREGION The region has no overlapping borders.