title: WPF Grid ColumnSpan content dynamic width reformating other content
body: <p>I know the title of this question is really confusing and also it is pretty hard to explain so I painted the following picture to explain what I am trying to reach.</p>
  
  <p>My layout has to have three columns with the same width (*). In each column there are going to be many different groups with static content. I want the group title to extend over all three column if it is too long. Then there is also the checkbox on the right of every group title in each column that is then supposed to displayed under the title but still on the right side.</p>
  
  <p><a href="https://i.stack.imgur.com/tkAye.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/tkAye.png" alt="The grid"></a></p>
  
  <p>I've tried many different ways to achieve this and even ended up trying out datatriggers to set the grid row.</p>
  
  <p>My current approach was having the subtitle columnspan on 3 again and try to have the checkboxes move out of the way if there's no space.</p>
  
  <pre><code>&lt;Grid ShowGridLines="True"&gt;
      &lt;Grid.ColumnDefinitions&gt;
          &lt;ColumnDefinition Width="*"/&gt;
          &lt;ColumnDefinition Width="*"/&gt;
          &lt;ColumnDefinition Width="*"/&gt;
      &lt;/Grid.ColumnDefinitions&gt;
      &lt;Grid.RowDefinitions&gt;
          &lt;RowDefinition Height="Auto"/&gt;
          &lt;RowDefinition Height="Auto"/&gt;
          &lt;RowDefinition Height="Auto"/&gt;
      &lt;/Grid.RowDefinitions&gt;
      &lt;TextBlock Grid.Column="0" Text="Title 0"/&gt;
      &lt;TextBlock Grid.Column="1" Text="Title 1"/&gt;
      &lt;TextBlock Grid.Column="2" Text="Title 2"/&gt;
      &lt;TextBlock Grid.ColumnSpan="3" Background="LawnGreen" Grid.Row="1" 
                 HorizontalAlignment="Left" Text="Subtitle 1"/&gt;
      &lt;CheckBox Grid.Row="1" HorizontalAlignment="Right" Content="Check"/&gt;
      &lt;CheckBox Grid.Row="1" Grid.Column="1" HorizontalAlignment="Right" Content="Check"/&gt;
      &lt;CheckBox Grid.Row="1" Grid.Column="2" HorizontalAlignment="Right" Content="Check"/&gt;
  &lt;/Grid&gt;
  </code></pre>
  
  <p>Thanks for the help, even if the answer is that this isnt possible. ^^</p>