The GetUpdateRgn function retrieves the update region of a window by copying it into the specified region. The coordinates of the update region are relative to the upper-left corner of the window (that is, they are client coordinates).
int GetUpdateRgn(
HWND hWnd, // handle of window
HRGN hRgn, // handle of region
BOOL bErase // erase background flag
);
The return value indicates the complexity of the resulting region; it can be one of the following values.
Value | Meaning |
---|---|
COMPLEXREGION | Region consists of more than one rectangle. |
ERROR | An error occurred. |
NULLREGION | Region is empty. |
SIMPLEREGION | Region is a single rectangle. |
The BeginPaint function automatically validates the update region, so any call to GetUpdateRgn made immediately after the call to BeginPaint retrieves an empty update region.
Windows CE: The bErase parameter is ignored, the window background is not erased and no drawing is done.
Windows NT: Requires version 3.1 or later.
Windows: Requires Windows 95 or later.
Windows CE: Requires version 1.0 or later.
Header: Declared in winuser.h.
Import Library: Use user32.lib.
Painting and Drawing Overview, Painting and Drawing Functions