[Bug] iOS label can't un-set text decorations when updating text at the same time

[Eilon]

Description

On iOS specifically, un-setting TextDecoration (such as removing StrikeThrough) is a no-op when the Text is updated at the same time. Android works fine. It's probably not just the Text property but it does repro that way.

Steps to Reproduce

1. Use iOS Simulator
2. Have a label with some text
3. Via a Button (or whatever), change the label's text and SET TextDecoration=TextDecorations.Strikethrough.
4. Via a Button (or whatever), change the label's text and SET TextDecoration=TextDecorations.None.

If you DON'T change the label's text at the same time, then it works (strikethrough will get set, and then un-set).

Possibly related, but unsure:

• TextDecorations Strikethrough not called for FormattedText in iOS #5801 (closed, but someone seems to say it's not working)
• [Bug] TextDecorations don't work #8272 (closed)
• [Bug] TextDecoration Strikethrough not working on iOS together with LineHeight #11829 (open, but sounds a bit different)

Expected Behavior

Label's text should change every time, and the text decorations should change every time

Actual Behavior

Label's text changes but the strikethrough style never un-sets (it always stays as Strikethrough). Same happens with Underline.

Basic Information

• Version with issue:

   <PackageReference Include="Xamarin.Forms" Version="4.8.0.1269" />

• Last known good version: Don't know.
• IDE: VS2019 on Windows
• Platform Target Frameworks:
  • iOS: Latest?
  • Android: Latest?

Screenshots

Repro code

Start with basic XAML app.

Use this XAML in the MainPage:

    <StackLayout>
        <Label FontSize="16" Padding="30,24,30,0" x:Name="NiceLabel" Text="Default text" />
        <Button Clicked="Button_Clicked" Text="Toggle" />
    </StackLayout>

And this C# for MainPage's codebehind:

    public partial class MainPage : ContentPage
    {
        public MainPage()
        {
            InitializeComponent();

            // Initialize label
            UpdateLabel();
        }

        private bool _isStrikethrough;

        private void Button_Clicked(object sender, EventArgs e)
        {
            // Toggle strike-through and update label
            _isStrikethrough = !_isStrikethrough;
            UpdateLabel();
        }

        private void UpdateLabel()
        {
            NiceLabel.TextDecorations = _isStrikethrough ? TextDecorations.Strikethrough : TextDecorations.None;

            // Comment out the next line and it starts working again
            NiceLabel.Text = "Is it strikethrough? " + _isStrikethrough.ToString();
        }
    }

Workaround

Unknown

[feokuma]

Maybe I've a related bug. I have a Label using TextDecorations.Underline and when I change the text then a can't remove the underline anymore. But if I doesn't change the text, I can control the TextDecorations normally.

[Cacuci]

I have same problem in Android. I am using Xamarin.Forms" Version="4.8.0.1364".

[JVHE]

I found a dirty bypass solution of this.

1. Declare two labels in the area where you want to use strikethrough.
2. Use the existing settings for one label.
3. For the other label, set strikethrough and any other options you want to set.
4. And use the IsVisible property to adjust the desired state.

this is a sample code

public class MyLabelLayout : Layout<View>
{
    private readonly Label _label;
    // since TextDecorations.Strikethrough can't remove when is set, so declared one more label which contains Strikethrough property
    private readonly Label _labelWithStrikethrough;

    private bool _isStrikethrough;
    public bool IsStrikethrough
    {
        get => _isStrikethrough;
        set
        {
            if (_isStrikethrough == value) return;
            UpdateLabel(value);
        }
    }

    private void UpdateLabel(bool isStrikethrough)
    {
        _label.IsVisible = !isStrikethrough;
        _labelWithStrikethrough.IsVisible = isStrikethrough;
    }

    public MyLabelLayout(bool isStrikethrough = false)
    {
        _label = new Label
        {
              // label properties...
              TextDecorations = TextDecorations.None
        };
        Children.Add(_label);

        _labelWithStrikethrough = new Label
        {
              // label properties...
              TextDecorations = TextDecorations.Strikethrough
        };
        Children.Add(_labelWithStrikethrough);

        _label.SetBinding(Label.TextProperty, "MyText");
        _labelWithStrikethrough .SetBinding(Label.TextProperty, "MyText");

        IsStrikethrough = isStrikethrough;
        UpdateLabel(isStrikethrough);
    }

    protected override SizeRequest OnMeasure(double widthConstraint, double heightConstraint)
    {
        return _label.Measure(widthConstraint, heightConstraint);
    }

    protected override void LayoutChildren(double x, double y, double width, double height)
    {
        _label.Layout(new Rectangle(x, y, width, height));
        _labelWithStrikethrough .Layout(new Rectangle(x, y, width, height));
    }
}

Of course, you can write better code than this simple code I wrote. Hope you use it well.

The regrettable thing I think while using Xamarin is that many functions that I expect to work naturally do not work properly. So I spend a lot of time implementing such a bypass workaround, and the codebase is getting bigger. Of course, you'll be busy spending a lot of time solving a lot of high-priority tasks, but I think that if there is no guarantee that someday these trivial problems will be solved, I might give up on Xamarin and move on to other frameworks or native development. I am sorry to say this without even contributing to this.

[lucafederli]

Any updates on this issue?

[danielroth1]

Workaround: Use Label.FormattedText instead of Label.Text
#8272 (comment)
#8272 (comment)

[jfversluis]

Hey everyone, I know it's been a while, thanks for your patience.

I have a PR out for this, you can find it at (#14907) if anyone is still willing or able to test this, please follow these instructions. Since the Label is a widely used control I would want to test this very well to make sure this doesn't break anything.

Please let me know, thanks! :)