This function sets the Local clipping region to the intersection of the specified rectangular region and the currently defined Local clipping region.
int x1 Horizontal location of the upper left corner of the local clipping region
int y1 Vertical location of the upper left corner of the local clipping region.
int x2 Horizontal location of the lower right corner of the local clipping region
int y2 Vertical location of the lower right corner of the local clipping region.