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GetUpdateRgn function

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).

Syntax


int GetUpdateRgn(
  _In_ HWND hWnd,
  _In_ HRGN hRgn,
  _In_ BOOL bErase
);

Parameters

hWnd [in]

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

hRgn [in]

Handle to the region to receive the update region.

bErase [in]

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 value

The return value indicates the complexity of the resulting region; it can be one of the following values.

ValueMeaning
COMPLEXREGIONRegion consists of more than one rectangle.
ERRORAn error occurred.
NULLREGIONRegion is empty.
SIMPLEREGIONRegion 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.

Requirements

Minimum supported client

Windows 2000 Professional [desktop apps only]

Minimum supported server

Windows 2000 Server [desktop apps only]

Header

Winuser.h (include Windows.h)

Library

User32.lib

DLL

User32.dll

See also

Painting and Drawing Overview
Painting and Drawing Functions

 

 

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