Dmitry Timoshkov dmitry@codeweavers.com writes:
If there is no current clipping region ExtSelectClipRgn(hdc, hrgn, RGN_DIFF) creates its own default clipping region which in most cases doesn't match neither a visible region nor the window extents attached to the DC.
It will get intersected with the visible region anyway, so it shouldn't matter as long as it's large enough. Why does it make a difference?