SetLocalClipping

This function sets clipping region within a particular window.

    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.