GetWindowRgn

The GetWindowRgn function obtains a copy of the window region of a window. The window region of a window is set by calling the SetWindowRgn function. The window region determines the area within the window where the system permits drawing. The system does not display any portion of a window that lies outside of the window region 

int GetWindowRgn(
  HWND hWnd, // handle to window whose window region is to be 
             // obtained
  HRGN hRgn  // handle to region that receives a copy of the window 
             // region
);

Parameters

hWnd
Handle to the window whose window region is to be obtained.
hrgn
Handle to a region. This region receives a copy of the window region.

Return Values

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

Value Meaning
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.

Remarks

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 the SetWindowRgn function.

QuickInfo

  Windows NT: Requires version 3.51 or later.
  Windows: Requires Windows 95 or later.
  Windows CE: Unsupported.
  Header: Declared in winuser.h.
  Import Library: Use user32.lib.

See Also

Painting and Drawing Overview, Painting and Drawing Functions, SetWindowRgn