utility function to create layout with the default font. Size and
        alignment parameters are shortcuts to according functions of the
        pango.Layout

def create_layout(self, size = None):
        """utility function to create layout with the default font. Size and
        alignment parameters are shortcuts to according functions of the
        pango.Layout"""
        if not self.context:
            # TODO - this is rather sloppy as far as exception goes
            #        should explain better
            raise Exception("Can not create layout without existing context!")

        layout = pangocairo.create_layout(self.context)
        font_desc = pango.FontDescription(_font_desc)
        if size: font_desc.set_absolute_size(size * pango.SCALE)

        layout.set_font_description(font_desc)
        return layout