title: Need help understanding size_hint in kivy
body: <p>I was was wondering if I get get an explanation on how size_hint works in Kivy. From my understanding, it is the relative scale from the widget, to its parent layout. I tried the following code:</p>
  
  <pre><code>    class TestFrame(GridLayout):
          def __init__(self, **kwargs):
              GridLayout.__init__(self, **kwargs)
              self.rows = 1
              self.add_widget(Label(text='test_num', size=(100, 25), size_hint=(.10, None)))
              self.add_widget(Label(text='test_txt', size=(100, 25), size_hint=(.75, None)))
              self.add_widget(Button(text='test_btn', size=(100, 25), size_hint=(.15, None)))
  </code></pre>
  
  <p>This is what I expect:</p>
  
  <pre><code>    |----------------------------------------------------------------------|
      |Test_num :                       Test_txt                :  Test_btn  |
  </code></pre>
  
  <p>Instead this is the result:</p>
  
  <pre><code>    |----------------------------------------------------------------------|
      |                                    Test_num :  Test_txt   : Test_btn |
  </code></pre>
  
  <p>I've played with different combinations of size_hint and size and end up with very similar results. What am I missing or not understanding?</p>