'Make sure _._pixmap is at least width, height,
create new pixmap if necessary'

def _pixmap_prepare(self, width, height):

    create_pixmap = False
    if (width > self._pixmap_width):
        self._pixmap_width = max(int((self._pixmap_width * 1.1)), width)
        create_pixmap = True
    if (height > self._pixmap_height):
        self._pixmap_height = max(int((self._pixmap_height * 1.1)), height)
        create_pixmap = True
    if create_pixmap:
        self._pixmap = gdk.Pixmap(self.window, self._pixmap_width, self._pixmap_height)
        self._renderer.set_pixmap(self._pixmap)
