import cairo

class Gauge():
    __slots__ = 'min_value', 'max_value', 'value',

    def __init__(self, min_value: float, max_value: float):
        self.min_value: float = min_value
        self.max_value: float = max_value
        self.value: float     = min_value

    def set_value(self, value):
        self.value = value

    def draw_bg(self, cr: cairo.Context):
        raise NotImplementedError

    def draw_fg(self, cr: cairo.Context):
        raise NotImplementedError