更好的Kivy单击拖动和绘制线

Question

这是一个较大的应用程序的一个小组件，在单击，拖动和释放时绘制一条线：

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.core.window import Window
from kivy.graphics import Color, Line, Rectangle

Window.set_system_cursor('crosshair')

DRAG_START = ()
DRAG_END = ()
DRAGGING = False


class Widget(BoxLayout):
    def __init__(self, **kwargs):
        super(Widget, self).__init__(**kwargs)
        Window.bind(mouse_pos=self.mouse_pos)
        self.bind(pos=self.draw)
        self.bind(size=self.draw)
        self.layout1 = BoxLayout(opacity=1)
        self.add_widget(self.layout1)

    def draw(self, *args):
        self.layout1.canvas.clear()
        with self.canvas.before:
            Color(0.6, 0.6, 0.6, 1)
            self.bg = Rectangle(pos=self.pos, size=self.size)

    def drawLine(self, mPos):
        self.canvas.clear()
        with self.canvas:
            Color(0, 0, 0, 1)
            Line(
                points=[DRAG_START[0], DRAG_START[1], mPos[0], mPos[1]],
                width=1.4)

    def mouse_pos(self, window, pos):
        if DRAGGING == True:
            self.drawLine(pos)

    def on_touch_down(self, event):
        global DRAGGING, DRAG_START
        DRAGGING = True
        DRAG_START = event.pos

    def on_touch_up(self, event):
        global DRAGGING, DRAG_END
        DRAGGING = False
        DRAG_END = event.pos


class App(App):
    title = "Kivy Click Drag Line"

    def build(self):
        return Widget()


if __name__ == "__main__":
    App().run()

结果是 ：

虽然这有效，但我的问题是如果有更好的方法在python中做这个（对使用kivy语言不感兴趣）我有点怀疑我正在使用的全局变量以及在窗口小部件中观察到的事件。

谢谢 ！