The IntersectClipRect function creates a new clipping region from the intersection of the current clipping region and the specified rectangle.
int IntersectClipRect(
| HDC hdc, | // handle of device context | 
| int nLeftRect, | // x-coordinate of upper-left corner of rectangle | 
| int nTopRect, | // y-coordinate of upper-left corner of rectangle | 
| int nRightRect, | // x-coordinate of lower-right corner of rectangle | 
| int nBottomRect | // y-coordinate of lower-right corner of rectangle | 
| ); | 
The return value specifies the new clipping region’s type and can be any one of the following values:
| Value | Meaning | 
| NULLREGION | Region is empty. | 
| SIMPLEREGION | Region is a single rectangle. | 
| COMPLEXREGION | Region is more than one rectangle. | 
| ERROR | An error occurred. (The current clipping region is unaffected.) | 
The lower and rightmost edges of the given rectangle are excluded from the clipping region.