title: Viewbox containing a TextBlock seems to have minimum height
body: <p>I'm trying to build a UI layout in WPF that can scale with the size of the window. The idea is to have a number of controls on the left, a number of controls on the right, and in the middle, have a line of text. It's OK if the line of text is cropped on the right. The main thing is that the aspect ratio of all of the controls is maintained.</p>
  
  <p>That part is working fine. The problem is that the center line of text seems to have a minimum height; below this height, it will start clipping vertically. I want the text to keep shrinking if I make the window very thin. Even manually setting the <code>FontSize</code> on the <code>TextBlock</code> doesn't work.</p>
  
  <p>Note that the controls on the left and right do not have a minimum width; they can shrink indefinitely.</p>
  
  <p>My XAML is here. I'm using .NET 4.0.</p>
  
  <pre><code>&lt;Window x:Class="TestWpfApp.MainWindow"
          xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
          xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
          Title="MainWindow" Height="75" Width="525"&gt;
      &lt;Grid&gt;
          &lt;Grid.ColumnDefinitions&gt;
              &lt;ColumnDefinition Width="Auto"/&gt;
              &lt;ColumnDefinition Width="1*"/&gt;
              &lt;ColumnDefinition Width="Auto"/&gt;
          &lt;/Grid.ColumnDefinitions&gt;
          &lt;Viewbox Grid.Column="0" Stretch="UniformToFill" Margin="2"&gt;
              &lt;Grid&gt;
                  &lt;Grid.ColumnDefinitions&gt;
                      &lt;ColumnDefinition/&gt;
                      &lt;ColumnDefinition/&gt;
                      &lt;ColumnDefinition/&gt;
                      &lt;ColumnDefinition/&gt;
                  &lt;/Grid.ColumnDefinitions&gt;
                  &lt;Button Grid.Column="0" Grid.Row="0" HorizontalAlignment="Center" VerticalAlignment="Center"&gt;A&lt;/Button&gt;
                  &lt;Button Grid.Column="1" Grid.Row="0" HorizontalAlignment="Center" VerticalAlignment="Center"&gt;B&lt;/Button&gt;
                  &lt;Button Grid.Column="2" Grid.Row="0" HorizontalAlignment="Center" VerticalAlignment="Center"&gt;C&lt;/Button&gt;
                  &lt;Button Grid.Column="3" Grid.Row="0" HorizontalAlignment="Center" VerticalAlignment="Center"&gt;D&lt;/Button&gt;
              &lt;/Grid&gt;
          &lt;/Viewbox&gt;
  
          &lt;Viewbox VerticalAlignment="Top" HorizontalAlignment="Left" Grid.Column="1" Stretch="UniformToFill" Margin="2"&gt;
              &lt;TextBlock&gt;Here is a bunch of text that may prove to be interesting.&lt;/TextBlock&gt;
          &lt;/Viewbox&gt;
  
          &lt;Viewbox Grid.Column="2" Stretch="UniformToFill" Margin="2"&gt;
              &lt;Button HorizontalAlignment="Center"&gt;X&lt;/Button&gt;
          &lt;/Viewbox&gt;
      &lt;/Grid&gt;
  &lt;/Window&gt;
  </code></pre>