InvalidateRgn
InvalidateRgn is a function in Microsoft Windows programming environments, commonly used with the Windows API. Its primary purpose is to mark a region of a window's client area as invalid. When a region is marked as invalid, it means that the content within that area is no longer considered up-to-date or accurate and needs to be redrawn.
The function takes a window handle and a region handle as parameters. The window handle identifies the
Invalidating a region does not immediately cause the window to redraw. Instead, it adds the specified region