int IntersectRect( LPRECT lpRect1, LPRECT lpRect2 );
lpRect1
Points to a RECT or CRect that contains a source rectangle.
lpRect2
Points to a RECT or CRect that contains a source rectangle.
Makes the CRect equal to the intersection of two existing rectangles. The intersection is the largest rectangle contained in both existing rectangles.
TRUE if the intersection of the two rectangles is not empty. It is FALSE if the intersection is empty.
::IntersectRect, CRect::operator &=, CRect::operator &