d_y_zoom'>y_zoom</span> <span class='op'>=</span> <span class='id identifier rubyid_zoom_factor'>zoom_factor</span>
  <span class='id identifier rubyid_cur_source_right'>cur_source_right</span> <span class='op'>=</span> <span class='ivar'>@source_x</span> <span class='op'>+</span> <span class='ivar'>@source_w</span>
  <span class='id identifier rubyid_cur_source_top'>cur_source_top</span>   <span class='op'>=</span> <span class='ivar'>@source_y</span> <span class='op'>+</span> <span class='ivar'>@source_h</