Allow control to grow, but not to shrink

Question

I basically have a setup like this:

<GroupBox>
  <TextBlock Name="tbValue"/>
</GroupBox>

The content of the TextBlock changes very often (displaying a measure value from a sensor). This leads to the width of the groupbox changing all the time which looks&feels like crap.

Does anyone have an idea how i could make the groupbox grow automatically when the text changes, but not shink again whenever the text gets shorter again?

Answer 1

Can propose behavior. Raw sample

public class GrowOnlyWidthBehavior : Behavior<FrameworkElement>
{
    protected override void OnAttached()
    {
        base.OnAttached();
        AssociatedObject.SizeChanged += OnSizeChanged;
    }

    private void OnSizeChanged(object sender, SizeChangedEventArgs e)
    {
        AssociatedObject.MinWidth = Math.Max(AssociatedObject.MinWidth, AssociatedObject.ActualWidth);
    }
}

Updated behavior. Thanks to AndrewS for pointing to the error in previous code. I used logic from HighCore 's answer.

Answer 2

Just handle the SizeChanged event and set the GroupBox 's MinWidth property to the largest between the MinWidth and the ActualWidth :

<GroupBox SizeChanged="GroupBox_SizeChanged">
    <TextBlock Name="tbValue"/>  
</GroupBox>

Code behind:

private void GroupBox_SizeChanged(object sender, SizeChangedEventArgs e)
{
    var gb = sender as GroupBox;
    gb.MinWidth = Math.Max(gb.MinWidth, gb.ActualWidth);
}