vinipsmaker

if ( A.connected(B) ) {
    if ( !C.connected(D) ) {
        bool foreign_is_contour = edge(C, D).contour();
 
        // the number of contour edges
        switch ( edge(A, C).contour()
                 + edge(B, D).contour()
                 + foreign_is_contour ) {
        case 2:
            A.smooth = !foreign_is_contour;