Retrieves the update region into a region identified by pRgn.
int GetUpdateRgn(
   CRgn* pRgn,
   BOOL bErase = FALSE 
);
Parameters
- pRgn 
 Identifies the update region.
- bErase 
 Specifies whether the background will be erased and nonclient areas of child windows will be drawn. If the value is FALSE, no drawing is done.
Return Value
Specifies a short-integer flag that indicates the type of resulting region. The value can take any one of the following:
- SIMPLEREGION The region has no overlapping borders. 
- COMPLEXREGION The region has overlapping borders. 
- NULLREGION The region is empty. 
- ERROR No region was created. 
Remarks
The coordinates of this region are relative to the upper-left corner (client coordinates).
The BeginPaint member function automatically validates the update region, so any call to GetUpdateRgn made immediately after a call to BeginPaint retrieves an empty update region.
Requirements
Header: afxwin.h