function set_containing_block($x = null, $y = null, $w = null, $h = null)
 {
     parent::set_containing_block($x, $y, $w, $h);
     if (isset($h)) {
         $this->_bottom_page_margin = $h;
     }
 }
 /**
  * Set the frame's containing block.  Overridden to set $this->_bottom_page_margin.
  *
  * @param float $x
  * @param float $y
  * @param float $w
  * @param float $h
  */
 function set_containing_block($x = null, $y = null, $w = null, $h = null)
 {
     parent::set_containing_block($x, $y, $w, $h);
     //$w = $this->get_containing_block("w");
     if (isset($h)) {
         $this->_bottom_page_margin = $h;
     }
     // - $this->_frame->get_style()->length_in_pt($this->_frame->get_style()->margin_bottom, $w);
 }