def _draw_text(ctx, text, align_point=0.0, size=1.0, rgba=(0.0, 0.0, 0.0, 1.0)
    ):
    """
	Draw the desired text centered vertically around (0,0) horizontally
	"align_point" along the text's width.
	"""
    ctx.save()
    ctx.select_font_face('Sans')
    ctx.set_source_rgba(*rgba)
    ctx.set_font_size(size)
    x, y, w, h, _w, _h = ctx.text_extents(text)
    ctx.move_to(-x + (1.0 - w) * align_point, -y - size / 2)
    ctx.show_text(text)
    ctx.restore()
