Return the pixel span height of the scrollbar area in which
        the slider handle may move

def get_scrollbar_position_height(self):
        """Return the pixel span height of the scrollbar area in which
        the slider handle may move"""
        vsb = self.editor.verticalScrollBar()
        style = vsb.style()
        opt = QStyleOptionSlider()
        vsb.initStyleOption(opt)

        # Get the area in which the slider handle may move.
        groove_rect = style.subControlRect(
                QStyle.CC_ScrollBar, opt, QStyle.SC_ScrollBarGroove, self)

        return float(groove_rect.height())