Fix: Hypelinks not clickable in RichTextBox under Silverlight

Just fixed a nasty bug in ClipFlair Studio (http://studio.clipflair.net), where one couldn’t click hyperlinks in the Text component when set at ReadOnly mode. In that mode hyperlinks should open up new web pages (in Edit mode you can edit/remove them only of course), but instead when clicked they would show something like a focus rectangle (which they normally never show).

The situation was hard to debug since it wasn’t obvious what had caused the issue (it was working some time ago). I eventually found out that when the RichTextBox in Silverlight (may occur in WPF and WinRT too, haven’t tried) has a Transparent background, then Hyperlinks in it let MouseLeftButtonDown events pass through, so OnMouseLeftButtonDown will fire at their visual parent (or other visual ancestor) if no component in the visual chain marks the event as handled (such events bubble up towards the top of the visual hierarchy/containment chain).

This shouldn’t be much of a problem, if there wasn’t another issue, where if the ancestor called CaptureMouse in their OnMouseLeftButtonDown overriden method (from Control class), which is usual in mouse dragging code (in my case it was a FloatingWindow [TextWindow] that was the visual ancestor of RichTextBox), the hyperlink fails to fire when clicked and shows that weird solid-line border arround it instead.

The fix was easy once I knew what was happening, I attached a MouseLeftButtonDown event handler to the RichTextBox (if one was subclassing it [assuming it allows to do so] they could also have opted to add an overriden OnMouseLeftButtonDown method) that sets Handled property of the event parameter to true to consume it. The fix is available at CodePlex.

One can verify that the fix works now by downloading a sample ClipFlair Activity from https://www.dropbox.com/s/1zr36190xb0m6vk/Test_Text_URLs.clipflair and opening it in ClipFlair Studio. Can also download and build/run the source code of the previous broken version 1faaa8b35749 and test with that save activity file to see that the URLs didn’t open before when clicked but showed a rectangle arround them intead.

HowTo: Clear contents of Silverlight’s RichTextBox control

Was just debugging an issue with loading of saved state at ClipFlair’s Text component, when I realized that Silverlight’s (and WPF’s) RichTextBox control doesn’t accept an empty string at its Xaml proprerty to clear its contents as one would expect. Instead clearing the contents of the RichTextBox requires a call to Blocks.Clear().

In ClipFlair’s case, the Text component (a FloatingWindow descendent) hosts a SilverTextEditor control, which in turn hosts a RichTextBox named rtb and has its own Xaml property, where I added the needed logic to clear the RichTextBox contents when getting a null or empty string. Wonder why Microsoft couldn’t do the same thing.

    public string Xaml     {
      get { return rtb.Xaml; }
      set { 
        if (value != null && value.Trim() != "") rtb.Xaml = value; 
        else rtb.Blocks.Clear(); 
      } //allows to set null or blank value to clear the RichTextBox

    }