Kivy: dock demo

dockdemo.py

import kivy
kivy.require('1.9.0')

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

root = Builder.load_string('''
AnchorLayout:
    anchor_x: 'left'
    StackLayout:
        orientation: 'lr-tb'
        size_hint: None, None
        height: self.minimum_height
        width: 1

        Button:
            size_hint: None, None
            width: self.texture_size[0] + dp(12)
            height: self.texture_size[1] + dp(12)
            text: 'Hello, this is a long message here'

        Button:
            size_hint: None, None
            width: self.texture_size[0] + dp(12)
            height: self.texture_size[1] + dp(12)
            text: 'Hello world'

        Widget:
            size_hint_y: None
            height: dp(12)

        Button:
            size_hint: None, None
            width: self.texture_size[0] + dp(12)
            height: self.texture_size[1] + dp(12)
            text: 'Bye'
''')

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

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