Wpf localization dynamic Subscript for TextBlock

Question

I'm using MVVM pattern to bind text to TextBlock. The text is defined in database with <Subscript> tag to define when the text is Subscript. "Some<Subscript>subscript</Subscript>text."

I tried using Unicode subscripts and superscripts, but the characters appears too small, and hard to read.

I couldn't find a direct way to do this. any suggestions?

score 1 · Answer 1 · answered Jan 07 '18 at 13:15

When you know that there is a subscription Tag you may use several Runs within your TextBlock.

<TextBlock>
   <Run />
   <Run />
</TextBlock>

I think you do not know the exact position of the subscripted text, right? So, why not just analyze your input and creating a new Run programatically? The Runs with the normal text have another size than Runs with subscripted text.

If you need help with adding Runs programatically just have a look at this StackOverflow post: How to assign a Run to a text property, programmatically?

I know this is not the best way in MVVM to define XAML controls in your ViewModel, but thats the fastest way to reach better legibility.

Hey man, thanks for your reply. You are correct, I don't know the position of the subscript. and I'm trying to avoid any UI Controls inside my ViewModel. — IBRA, Jan 07 '18 at 13:24
No problem. This might be just the way to go when no other solution helps ;-) — Mark, Jan 07 '18 at 13:34

score 0 · Accepted Answer · answered Jan 08 '18 at 13:37

Using Attached properties fixed my problem in the most MVVM friendly way. You get the text and add to the TextBlock Inlines as you want.

Attached property c#:

public static class TextBlockAp {
    public static readonly DependencyProperty SubscriptTextProperty = DependencyProperty.RegisterAttached(
        "SubscriptText", typeof(string), typeof(TextboxAttachedProperty), new PropertyMetadata(OnSubscriptTextPropertyChanged));

    public static string GetSubscriptText(DependencyObject obj) {
        return (string)obj.GetValue(SubscriptTextProperty);
    }

    public static void SetSubscriptText(DependencyObject obj, string value) {
        obj.SetValue(SubscriptTextProperty, value);
    }

    private static void OnSubscriptTextPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) {
        try {
            var value = e.NewValue as string;
            if (String.IsNullOrEmpty(value)) return;
            var textBlock = (TextBlock)d;

            var startTag = "<Subscript>";
            var endTag = "</Subscript>";
            var subscript = String.Empty;
            if (value.Contains(startTag) && value.Contains(endTag)) {
                int index = value.IndexOf(startTag) + startTag.Length;
                subscript = value.Substring(index, value.IndexOf(endTag) - index);
            }

            var text = value.Split(new[] { startTag }, StringSplitOptions.None);
            textBlock.Inlines.Add(text[0]);
            Run run = new Run($" {subscript}") { BaselineAlignment = BaselineAlignment.Subscript, FontSize = 9 };
            textBlock.Inlines.Add(run);
        } catch (Exception ex) {
            if (ExceptionUtilities.UiPolicyException(ex)) throw;
        }
    }
}

xaml

<TextBlock ap:TextBlockAp.SubscriptText="{Binding MyProperty}" />

It needs more refactoring to work correctly, but it's a start.

Wpf localization dynamic Subscript for TextBlock

2 Answers2