#include <stdlib.h>
#include <grass/raster.h>

int 
black_and_white_line (int c1, int c2, int screen_x, int screen_y, int cur_screen_x, int cur_screen_y)
{
    if(abs(screen_y-cur_screen_y) <= abs(screen_x-cur_screen_x))
    {
        if (screen_x > cur_screen_x)
            R_standard_color(c1) ;
        else
            R_standard_color(c2) ;
        R_move_abs(cur_screen_x, cur_screen_y) ;
        R_cont_abs(screen_x, screen_y) ;

        if (screen_x > cur_screen_x)
            R_standard_color(c2) ;
        else
            R_standard_color(c1) ;
        R_move_abs(cur_screen_x, cur_screen_y-1) ;
        R_cont_abs(screen_x, screen_y-1) ;
    }
    else
    {
        if (screen_y > cur_screen_y)
            R_standard_color(c1) ;
        else
            R_standard_color(c2) ;
        R_move_abs(cur_screen_x, cur_screen_y) ;
        R_cont_abs(screen_x, screen_y) ;
        if (screen_y > cur_screen_y)
            R_standard_color(c2) ;
        else
            R_standard_color(c1) ;
        R_move_abs(cur_screen_x+1, cur_screen_y) ;
        R_cont_abs(screen_x+1, screen_y) ;
    }
    
    R_stabilize() ;

    return 0;
}