WPF MeasureOverride not working for my Custom Control

Question

I have a custom control that is "hosted" in a custom panel (both mine).

My custom panel has code like this:

protected override Size MeasureOverride(Size availableSize)
{
  foreach (UIElement child in Children)
  {
     child.Measure(availableSize);

     // Do stuff with the Desired Size.  (This is an example)
     resultSize.Width += child.DesiredSize.Width;
     resultSize.Height = Math.Max(resultSize.Height, child.DesiredSize.Height);

  }
  //.. Other Measure Stuff
}

All the standard controls I put in my panel work fine. But my custom control has DesiredSize set to a very small width (5 pixels). Even though it has a Label on it that wants at least 40 pixels to be able to show.

So I put this code into my custom control:

protected override Size MeasureOverride(Size constraint)
{
    var baseSize = base.MeasureOverride(constraint);
    var labelTextWidth = GetStringWidth(label.Content.ToString(), label);

    if (baseSize.Width == 0)
        baseSize.Width = 100;

    if (baseSize.Width < labelTextWidth)
        baseSize.Width = labelTextWidth;

    return baseSize;
}

This returns a Size that is correct. But in my Panel's MeasureOverride, the child.DesiredSize does not reflect what I returned from my child control's MeasureOverride.

Any ideas why it would do that? And what I can do to get it to pass my calculated Measure to the panel correctly in the DesiredSize? (you can't just set DesiredSize.)

Please post the template of your custom control and also what you are getting as the availableSize in the measureoverride of your panel. — AndrewS
@AndrewS - The template of my custom panel is too large to post here (255 lines). I loaded it as a gist here: gist.github.com/Vaccano/5173613 . availableSize is {510, Infinity} — Vaccano

Sergey Sergey · Accepted Answer · 2015-01-12T16:20:39

If MeasureOverride of custom control return correct size, but it is not reflected in DesiredSize property, I have only one suggestions. Your child element is wrapped by some container, you can check type of child element inside MeasureOverride procedure of custom panel.

WPF MeasureOverride not working for my Custom Control

1 Answers