'Try to find a maximum font size that fits any strings within the height'

def fit_fontsize(self, heightlimit):

    self.ctx.set_font_size(heightlimit)
    (asc, desc, height, _, _) = self.font_extents()
    self.ctx.set_font_size(int(((heightlimit * heightlimit) / height)))
    return self.font_extents()
