GetUpdateRgn

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
);

Parameters

hWnd

Identifies the window with an update region that is to be retrieved.

hRgn

Identifies the region to receive the update region.

bErase

Specifies whether the window background should be erased and whether nonclient areas of child windows should be drawn. If this parameter is FALSE, no drawing is done.

Return Values

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.

Remarks

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.

See Also

GetUpdateRect, InvalidateRgn, UpdateWindow, ValidateRgn

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