cursor.py

from kivy.app import App
from kivy.factory import Factory as F
from kivy.core.window import Window as W


class CrossHairCursorApp(App):
    def build(self):
        root = F.Widget()
        with root.canvas.after:
            self.v_line = F.Line(points=[])
            self.h_line = F.Line(points=[])

        W.bind(mouse_pos=self.update_cursor)
        return root

    def update_cursor(self, window, mouse_pos):
        self.v_line.points = [mouse_pos[0], 0, mouse_pos[0], window.height]
        self.h_line.points = [0, mouse_pos[1], window.width, mouse_pos[1]]


if __name__ == '__main__':
    CrossHairCursorApp().run()