Listing 2 

/*
     clipLine() = draws the portion of a line that is      
                  within specified boundaries              
*/

void clipLine(int x1,int y1,int x2,int y2,int color)
{
    int xa,ya,xb,yb;

    if (x1 < x2)
    {
        xa = x1;
        ya = y1;
        xb = x2;
        yb = y2;
    }
    else
    {
        xa = x2;
        ya = y2;
        xb = x1;
        yb = y1;
    }
    if ((xa > xmax) || (xb < xmin))
        return(0);
    if (xa < xmin)
    {
        ya = ya + (long)(xmin - xa)*(yb - ya)/(xb - xa);
        xa = xmin;
    }
    if (ya < ymin)
    {
        xa = xa + (long)(ymin - ya)*(xb - xa)/(yb - ya);
        ya = ymin;
    }
    if (ya > ymax)
    {
        xa = xa + (long)(ymax - ya)*(xb - xa)/(yb - ya);
        ya = ymax;
    }
    if (xb > xmax)
    {
        yb = ya + (long)(xmax - xa)*(yb - ya)/(xb - xa);
        xb = xmax;
    }
    if (yb < ymin)
    {
        xb = xa + (long)(ymin - ya)*(xb - xa)/(yb - ya);
        yb = ymin;
    }
    if (yb > ymax)
    {
        xb = xa + (long)(ymax - ya)*(xb - xa)/(yb - ya);
        yb = ymax;
    }
    drawLine(xa,ya,xb,yb,color);
}