Kivy: texture_size demo

mixedtest.py

import kivy
kivy.require('1.8.1')

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

root = Builder.load_string('''
<TestButton@Button>:
    size_hint: None, None
    width: self.texture_size[0] + dp(16)
    height: self.texture_size[1] + dp(12)

FloatLayout:
    TestButton:
        pos: 100, 100
        text: 'hello'

    TestButton:
        pos: 300, 200
        text: 'longer button label'
''')

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

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