func: static int find_dirty_height(VncState *vs, int y, int last_x, int x)
  
  {
  
      int h;
  
  
  
      for (h = 1; h < (vs->serverds.height - y); h++) {
  
          int tmp_x;
  
          if (!vnc_get_bit(vs->dirty_row[y + h], last_x))
  
              break;
  
          for (tmp_x = last_x; tmp_x < x; tmp_x++)
  
              vnc_clear_bit(vs->dirty_row[y + h], tmp_x);
  
      }
  
  
  
      return h;
  
  }
  