This function calculates the intersection of two source rectangles and places the coordinates of the intersection rectangle into the destination rectangle.
If the source rectangles do not intersect, an empty rectangle (in which all coordinates are set to zero) is placed into the destination rectangle.
BOOL IntersectRect( LPRECT lprcDst, const RECT* lprcSrc1, const RECT* lprcSrc2 );
Long pointer to the RECT structure that is to receive the intersection of the rectangles pointed to by the lprcSrc1 and lprcSrc2 parameters.
Long pointer to the RECT structure that contains the first source rectangle.
Long pointer to the RECT structure that contains the second source rectangle.
Nonzero indicates that the rectangles intersect.
Zero indicates that the rectangles do not intersect.
To get extended error information, call GetLastError.