Unable to clear TextDecoration in Xamarin Forms UWP App - xamarin

Question

Using Xamarin Forms (version 2.5.0.121934), I'm working on an app targeting Android, iOS, and UWP. I need to add underlining and strikethrough to some text, which require custom renderers. For Android and iOS, everything is working fine, and on UWP, applying strikethrough or underline works correctly, but removing those decorations isn't working.
Here's the entirety of the UWP renderer:
[assembly: ExportRenderer(typeof(EnhancedLabel), typeof(EnhancedLabelRenderer))]
namespace myApp.UWP
{
public class EnhancedLabelRenderer : LabelRenderer
{
protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
{
base.OnElementPropertyChanged(sender, e);
var strikethrough = ((EnhancedLabel)sender).Strikethrough;
var underline = ((EnhancedLabel)sender).Underline;
if (strikethrough && underline)
{
Control.TextDecorations = TextDecorations.Strikethrough | TextDecorations.Underline;
}
else if (strikethrough)
{
Control.TextDecorations = TextDecorations.Strikethrough;
}
else if (underline)
{
Control.TextDecorations = TextDecorations.Underline;
}
else
{
Control.TextDecorations = TextDecorations.None;
}
}
}
}
EnhancedLabel is a simple class that extends Xamarin.Forms.Label and adds the simple BindableProperty fields that specify strikethrough or underlining.
The renderer is properly setting TextDecorations.None, but that isn't having an effect on the UI. I've worked through this in the debugger, and can actually see that the state of the TextBlock within the ExtendedLabel has TextDecorations.None, but the UI is still drawing it with underlining or strikethrough (essentially, either of those can be added, but neither can be removed).
I've gone through the Xamarin documentation and looked at the bugs in Bugzilla, and haven't found any clues. Has any one else encountered this? Wondering if there's a UWP-specific call I need to make that I missed, or if using TextDecorations is the wrong way to apply the styles, or if I've actually stumbled across a bug.

Answer 1

Bug in UWP as in Xaml below:
<TextBlock>
<Run Text="Decorations can be toggled on and off"/>
</TextBlock>
<TextBlock Text="Decorations will not toggle off"/>
It is the same issue if you code the TextBlock:
TextBlock textBlock = new TextBlock { FontSize = 18.0 };
textBlock.Inlines.Add(new Windows.UI.Xaml.Documents.Run { Text = "This text will not stick on text decoration." });
TextBlock textBlockBad = new TextBlock
{
FontSize = 18.0,
Text = "This text will not enable the TextDecorations to be turned off"
};
Same behaviour found with Typography.Capitals
Just need to use only Inlines for TextBlocks and presumably RichTextBlocks to avoid these issues.

Answer 2

Wondering if there's a UWP-specific call I need to make that I missed, or if using TextDecorations is the wrong way to apply the styles, or if I've actually stumbled across a bug.
If you want yo use TextDecorations, you could use the Run instance to pack the decorated text like the follow.
Underline ul = new Underline();
ul.TextDecorations = TextDecorations.Strikethrough;
Run r = new Run();
r.Text = "Here is an underlined text";
ul.Inlines.Add(r);
MyTextBlock.Inlines.Add(ul);
For you requirement, I have create a CustomLabel that you could use directly.
CustomLabel.cs
public class CustomLabel : Label
{
public static readonly BindableProperty DeckProperty = BindableProperty.Create(
propertyName: "Deck",
returnType: typeof(TextDeck),
declaringType: typeof(CustomLabel),
defaultValue: default(TextDeck));
public TextDeck Deck
{
get { return (TextDeck) GetValue(DeckProperty); }
set { SetValue(DeckProperty, value); }
}
}
public enum TextDeck
{
None = 0,
//
// Summary:
// Underline is applied to the text.
Underline = 1,
//
// Summary:
// Strikethrough is applied to the text.
Strikethrough = 2
}
CustomLabelRenderer.cs
public class CustomLabelRenderer : LabelRenderer
{
protected override void OnElementChanged(ElementChangedEventArgs<Label> e)
{
base.OnElementChanged(e);
if (Control != null)
{
var element = Element as CustomLabel;
var underline = new Underline();
var run = new Run();
switch (element.Deck)
{
case TextDeck.None:
underline.TextDecorations = TextDecorations.None;
break;
case TextDeck.Strikethrough:
underline.TextDecorations = TextDecorations.Strikethrough;
break;
case TextDeck.Underline:
underline.TextDecorations = TextDecorations.Underline;
break;
}
run.Text = element.Text;
underline.Inlines.Add(run);
Control.Inlines.Clear();
Control.Inlines.Add(underline);
}
}
}
Usage
<local:CustomLabel Deck="Underline" Text="Welcome to Xamarin.Forms!" />