public function get_margin_height()
    {
        $style = $this->_style;

        return (float)$style->length_in_pt(array(
            $style->height,
            $style->margin_top,
            $style->margin_bottom,
            $style->border_top_width,
            $style->border_bottom_width,
            $style->padding_top,
            $style->padding_bottom
        ), $this->_containing_block["h"]);
    }