Random flood fill

flood_fill.c

// create stack and other structures
stack_t* draw_stack = (stack_t*)malloc(sizeof(stack_t));
stack_init(draw_stack, (wa.width*wa.height));
stack_element_t random_start;

// push random position onto stack
random_start.x = rand()%wa.width;
random_start.y = rand()%wa.height;
stack_push(draw_stack, random_start);

// allocate 2d array for flood fill
int fill_array[wa.width][wa.height];

/* create a X11 graphics context for drawing in the window */
g = XCreateGC (dpy, root, 0, NULL);

int depth = 0;

while (filling)
  {
    
    if (stack_is_empty(draw_stack))
      {
        printf("done.");
        filling = false;
        XFlush(dpy);
        break;
      }
    else
      {
        // check for empty spots around the current pixel
        stack_element_t stack_top = stack_peek(draw_stack);
        int num_spots;
        stack_element_t* empty_spots = get_empty_spots(stack_top, fill_array, wa.width, wa.height, num_spots);
         
        // choose out of the empty spots randomly, draw, and continue looping
        if (num_spots > 0 && empty_spots != NULL)
          {
            XColor new_col;
            float d_r = (0.008 * depth);
            float d_g = (0.09 * depth);
            float d_b = (0.9 * depth);
            d_r = (d_r > 65535) ? 65535 : d_r;
            d_g = (d_g > 65535) ? 65535 : d_g;
            d_b = (d_b > 65535) ? 65535 : d_b;
            new_col.red = (65535 - d_r);
            new_col.green = (65535 - d_g);
            new_col.blue = (65535 - d_b);
            
            
            stack_element_t random_spot = empty_spots[rand()%num_spots];
            free (empty_spots);
            // allocate color, and set foreground
            XAllocColor(dpy, DefaultColormapOfScreen(DefaultScreenOfDisplay(dpy)), &new_col);
            XSetForeground(dpy, g, new_col.pixel);
            
            // draw pixel in random spot
            XDrawPoint(dpy, root, g, random_spot.x, random_spot.y);
            // fill array position
            fill_array[random_spot.y][random_spot.x] = 1;
             // add to top of stack
            stack_push(draw_stack, random_spot);
            depth++;              
          }
        // otherwise, there are no empty spots
        // so pop the stack and continue looping
        else
          {
            stack_pop(draw_stack);
            depth--;
          }
      }
    
    /* flush changes to screen and sleep */
    XFlush(dpy);
    usleep(15);
  }

free (data);
free (fill_array);
stack_cleanup(draw_stack);
free (draw_stack);