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Call this member function to get the window region of a window.

int GetWindowRgn(
   HRGN hRgn 



A handle to a window region.

The return value specifies the type of the region that the function obtains. It can be one of the following values:

  • NULLREGION   The region is empty.

  • SIMPLEREGION   The region is a single rectangle.

  • COMPLEXREGION   The region is more than one rectangle.

  • ERROR   An error occurred; the region is unaffected.

The window region determines the area within the window where the operating system permits drawing. The operating system does not display any portion of a window that lies outside of the window region.

The coordinates of a window's window region are relative to the upper-left corner of the window, not the client area of the window.

To set the window region of a window, call CWnd::SetWindowRgn.