test.py

#!/usr/bin/env python
from kivy.app import App
from kivy.uix.widget import Widget
from kivy.properties import ObjectProperty, NumericProperty
from kivy.lang import Builder

Builder.load_string('''
<ArrowPointer>:
    canvas:
        Color:
            rgb: 0, 0, 111 / 255.
        Line:
            points: self.x - self.offset, self.y - self.offset, self.x + self.offset, self.y + self.offset
''')

class ArrowPointer(Widget):
    arrow_tip = ObjectProperty(None)
    offset = NumericProperty(50)

class TestB(App):
    def build(self):
        return ArrowPointer()

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