grid.py 文件源码

def layout(self, width):
        surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, 1, 1)
        ctx = cairo.Context(surface)

        # calculate scale delta
        data_delta = self.__hi - self.__lo
        closest = 1
        while (closest*10) < data_delta:
            closest *= 10
        if (data_delta / closest) == 0:
            delta = closest
        elif(data_delta / closest) == 1:
            delta = closest / 10
        else:
            delta = closest
        start = self.__lo - (self.__lo % delta) + delta
        end = self.__hi - (self.__hi % delta)

        self.__delta = delta
        self.__width = width

        # calculate text height
        max_text_height = ctx.text_extents("ABCDEFGHIJKLMNOPQRSTUVWXYZabcedefghijklmnopqrstuvwxyz0123456789")[3]
        self.max_text_height = max_text_height
        height = max_text_height + 10
        self.__height = height