Overview
Group
Quick Info

Windows NT
Yes
Win95
Yes
Win32s
Yes
Import Library
user32.lib
Header File
winuser.h
Unicode
No
Platform Notes
None

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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