Kivy: square box test

squaretest.py

import kivy
kivy.require('1.8.1')

from kivy.app import App
from kivy.lang import Builder

root = Builder.load_string('''
BoxLayout:
    orientation: 'vertical'

    Label:
        text: 'hello'
        canvas.before:
            Color:
                rgba: 1, 0, 0, 1
            Rectangle:
                pos: self.pos
                size: self.size

    FloatLayout:
        Button:
            size_hint: None, None
            pos_hint: {'center': (0.5, 0.5)}
            aspect: self.parent.width / self.parent.height if self.parent.height else 1
            width: self.parent.width if self.aspect < 1 else self.parent.height
            height: self.parent.width if self.aspect < 1 else self.parent.height
            text: 'button'

    Label:
        text: 'goodbye'
        canvas.before:
            Color:
                rgba: 1, 0, 0, 1
            Rectangle:
                pos: self.pos
                size: self.size
''')

class TestApp(App):
    def build(self):
        return root

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