/************************************************************************/
/* Draw a line with a pattern using the 'slow' algorithm                */
/************************************************************************/

slow_pattern_line(x0, y0, x1, y1, color,pattern)
int     x0, y0, x1, y1, color, pattern;
        {
        int     x, y;
        static int mask[16] = {
                                0x8000,0x4000,0x2000,0x1000,
                                0x0800,0x0400,0x0200,0x0100,
                                0x0080,0x0040,0x0020,0x0010,
                                0x0008,0x0004,0x0002,0x0001};

        /*--- Draw degenerate line (pixel)                              */

        if (x0 == x1 && y0 == y1)               /* Draw a single pixel  */
                {
                if (mask[x0 & 15] & pattern)
                        pixel_write(x0, y0, color);
                }

        /*--- Draw lines with dx > dy                                   */

        else if (abs(x1 - x0) >= abs(y1 - y0))
                {                               /* Swap end points      */
                if (x1 < x0)
                        {
                        x = x1;
                        y = y1;
                        x1 = x0;
                        y1 = y0;
                        x0 = x;
                        y0 = y;
                        }
                for (x = x0; x <= x1; x++)      /* Loop over x coord    */
                    {                           /* Compute y using x    */
                y = y0 + ((x - x0)*(long)(y1 - y0))/(x1 - x0);
                if (mask[x & 15] & pattern)
                        pixel_write(x,y,color); /* Draw next point      */
                    }
                }

        /*--- Draw lines with dy > dx                                   */

        else
                {
                if (y1 < y0)                    /* Swap end points      */
                        {
                        x = x1;
                        y = y1;
                        x1 = x0;
                        y1 = y0;
                        x0 = x;
                        y0 = y;
                        }
                for (y = y0; y <= y1; y++)      /* Loop over y coord    */
                    {                           /* Compute x using y    */
                    x = x0 + ((y - y0)*(long)(x1 - x0))/(y1 - y0);
                    if (mask[y & 15] & pattern)
                        pixel_write(x,y,color);  /* Draw next point      */
                    }
                }
        }