I am trying to created a FormattedUltraButton based on the above suggestion and the custom uielement howto but i can't get it right. My code seems to work when i step through with a debugger but the visual result does not change at all. Here's my custom UIElementCreationFilter. Please advise.

    public void AfterCreateChildElements(UIElement parent)
    {
      var button = parent as UltraButtonUIElement;
      if (button == null)
      {
        return;
      }

      var originalTextElement = button.ImageAndTextElement.TextElement;

      var formattedTextElement = new FormattedTextUIElement(button.ImageAndTextElement)
      {
        Rect = new Rectangle(originalTextElement.Rect.Location, originalTextElement.Rect.Size),
        Value = new ParsedFormattedTextValue("This is a <b>test</b>")  // originalTextElement.Text
      };

      button.ImageAndTextElement.ChildElements.Remove(originalTextElement);
      button.ImageAndTextElement.ChildElements.Add(formattedTextElement);
    }

Thank you very much for your fast and interesting reply.

In the meantime i had found a solution on my own but it doesnt seem very elegant to me. Could you please give a bit of comparison and discussion of the both so i can learn from it?

      public void AfterCreateChildElements(UIElement parent)
      {
        var button = parent as UltraButtonUIElement;
        if (button == null)
        {
          return;
        }

        var originalUiElement = button.ImageAndTextElement;

        var replacementUiElement = new ImageAndFormattedTextUIElementEx(originalUiElement.Parent)
        {
          Rect = new Rectangle(originalUiElement.Rect.Location, originalUiElement.Rect.Size),
          TextHAlign = originalUiElement.TextHAlign,
          TextVAlign = originalUiElement.TextVAlign,
          Value = new ParsedFormattedTextValue(originalUiElement.Text)
        };

        button.ChildElements.Remove(originalUiElement);
        button.ChildElements.Add(replacementUiElement);
      }

Hi,

Well, one of the most obvious differences is that I used BeforeCreateChildElements instead of After, like you are doing. This is not really a big deal, but your way, the ImageAndTextUIElement and all of it's child elements are created and then you have to remove it. In my case, I am returning true from BeforeCreateChildElements, so the element never gets created in the first place. It's just a bit more efficient, but like I said, not really a big deal.

I am also placing the FormattedTextUIElement directly under the UltraBiuttonUIElement, which means the button won't show the Appearance.Image if you assigned one. I figured this was unlikely and you are probably not displaying an image on the button, anyway. You use of ImageAndFormattedTextUIElementEx might avoid that problem, but I am not entirely sure - it might work or it might not. If it doesn't work, it's likely because that element doesn't know how to get the Appearance.Image from the button because it's expecting to be a part of some other control. But I might be wrong.