Subscript / superscript in FormattedText class?

Question

I'm creating Text using the FormattedText class - but how can I subscript oder superscript Text when using this class? I found solution on how to do this when using a TextBlock, but I'm using FormattedText and not the TextBlock ): Thanks for any hint!

Answer 1

FormattedText can't do subscript/superscript - but TextFormatter can.

TextFormatter is a low level API, you need to write a lot of code to use it - but most of the code is just subclassing all the classes used to pass formatting parameters int TextFormatter.

How to use TextFormatter

TextFormatter takes a TextSource object and produces multiple TextLine objects (one for each line), the TextLine.Draw method can then be used to draw the line to a drawing context.

The TextSource class is abstract, you have to subclass it and override the GetTextRun method that simply returns a TextRun object that's in the character position provided.

TextRun is also abstract - but it does have subclasses you can use - the interesting class is TextCharacters that contains a string and formatting information.

The formatting information is in a TextRunProperties object, unfortunately, this is another abstract class you have to subclass.

TextRunProperties has a TypographyProperties property of type TextRunTypographyProperties.

TextRunTypographyProperties is yet another abstract class you need to subclass.

And finally TextRunTypographyProperties has the Variants property you can use like the TextBlock example.

Code Example

Here is the minimal code I could write to draw superscript text:

First, Our TextRunProperties and TextRunTypographyProperties that can return superscript font variant:

class CustomTextRunProperties : TextRunProperties
{
    private bool _superscript;
    public CustomTextRunProperties(bool superscript)
    {
        _superscript = superscript;
    }
    public override System.Windows.Media.Brush BackgroundBrush
    {
        get { return null; }
    }

    public override CultureInfo CultureInfo
    {
        get { return CultureInfo.CurrentCulture; }
    }

    public override double FontHintingEmSize
    {
        get { return 22; }
    }

    public override double FontRenderingEmSize
    {
        get { return 22; }
    }

    public override Brush ForegroundBrush
    {
        get { return Brushes.Black; }
    }

    public override System.Windows.TextDecorationCollection TextDecorations
    {
        get { return new System.Windows.TextDecorationCollection(); }
    }

    public override System.Windows.Media.TextEffectCollection TextEffects
    {
        get { return new TextEffectCollection(); }
    }

    public override System.Windows.Media.Typeface Typeface
    {
        get { return new Typeface("Calibri"); }
    }

    public override TextRunTypographyProperties TypographyProperties
    {
        get
        {
            return new CustomTextRunTypographyProperties(_superscript);
        }
    }

}

class CustomTextRunTypographyProperties : TextRunTypographyProperties
{
    private bool _superscript;

    public CustomTextRunTypographyProperties(bool superscript)
    {
        _superscript = superscript;
    }

    public override int AnnotationAlternates
    {
        get { return 0; }
    }

    public override bool CapitalSpacing
    {
        get { return false; }
    }

    public override System.Windows.FontCapitals Capitals
    {
        get { return FontCapitals.Normal; }
    }

    public override bool CaseSensitiveForms
    {
        get { return false; }
    }

    public override bool ContextualAlternates
    {
        get { return false; }
    }

    public override bool ContextualLigatures
    {
        get { return false; }
    }

    public override int ContextualSwashes
    {
        get { return 0; }
    }

    public override bool DiscretionaryLigatures
    {
        get { return false; }
    }

    public override bool EastAsianExpertForms
    {
        get { return false; }
    }

    public override System.Windows.FontEastAsianLanguage EastAsianLanguage
    {
        get { return FontEastAsianLanguage.Normal; }
    }

    public override System.Windows.FontEastAsianWidths EastAsianWidths
    {
        get { return FontEastAsianWidths.Normal; }
    }

    public override System.Windows.FontFraction Fraction
    {
        get { return FontFraction.Normal; }
    }

    public override bool HistoricalForms
    {
        get { return false; }
    }

    public override bool HistoricalLigatures
    {
        get { return false; }
    }

    public override bool Kerning
    {
        get { return true; }
    }

    public override bool MathematicalGreek
    {
        get { return false; }
    }

    public override System.Windows.FontNumeralAlignment NumeralAlignment
    {
        get { return FontNumeralAlignment.Normal; }
    }

    public override System.Windows.FontNumeralStyle NumeralStyle
    {
        get { return FontNumeralStyle.Normal; }
    }

    public override bool SlashedZero
    {
        get { return false; }
    }

    public override bool StandardLigatures
    {
        get { return false; }
    }

    public override int StandardSwashes
    {
        get { return 0; }
    }

    public override int StylisticAlternates
    {
        get { return 0; }
    }

    public override bool StylisticSet1
    {
        get { return false; }
    }

    public override bool StylisticSet10
    {
        get { return false; }
    }

    public override bool StylisticSet11
    {
        get { return false; }
    }

    public override bool StylisticSet12
    {
        get { return false; }
    }

    public override bool StylisticSet13
    {
        get { return false; }
    }

    public override bool StylisticSet14
    {
        get { return false; }
    }

    public override bool StylisticSet15
    {
        get { return false; }
    }

    public override bool StylisticSet16
    {
        get { return false; }
    }

    public override bool StylisticSet17
    {
        get { return false; }
    }

    public override bool StylisticSet18
    {
        get { return false; }
    }

    public override bool StylisticSet19
    {
        get { return false; }
    }

    public override bool StylisticSet2
    {
        get { return false; }
    }

    public override bool StylisticSet20
    {
        get { return false; }
    }

    public override bool StylisticSet3
    {
        get { return false; }
    }

    public override bool StylisticSet4
    {
        get { return false; }
    }

    public override bool StylisticSet5
    {
        get { return false; }
    }

    public override bool StylisticSet6
    {
        get { return false; }
    }

    public override bool StylisticSet7
    {
        get { return false; }
    }

    public override bool StylisticSet8
    {
        get { return false; }
    }

    public override bool StylisticSet9
    {
        get { return false; }
    }

    public override FontVariants Variants
    {
        get { return _superscript ? FontVariants.Superscript: FontVariants.Normal; }
    }
}

And a similar class for paragraph formatting (takes from MSDN TextFormatter sample):

class GenericTextParagraphProperties : TextParagraphProperties
{
    public GenericTextParagraphProperties(
       FlowDirection flowDirection,
       TextAlignment textAlignment,
       bool firstLineInParagraph,
       bool alwaysCollapsible,
       TextRunProperties defaultTextRunProperties,
       TextWrapping textWrap,
       double lineHeight,
       double indent)
    {
        _flowDirection = flowDirection;
        _textAlignment = textAlignment;
        _firstLineInParagraph = firstLineInParagraph;
        _alwaysCollapsible = alwaysCollapsible;
        _defaultTextRunProperties = defaultTextRunProperties;
        _textWrap = textWrap;
        _lineHeight = lineHeight;
        _indent = indent;
    }

    public override FlowDirection FlowDirection
    {
        get { return _flowDirection; }
    }

    public override TextAlignment TextAlignment
    {
        get { return _textAlignment; }
    }

    public override bool FirstLineInParagraph
    {
        get { return _firstLineInParagraph; }
    }

    public override bool AlwaysCollapsible
    {
        get { return _alwaysCollapsible; }
    }

    public override TextRunProperties DefaultTextRunProperties
    {
        get { return _defaultTextRunProperties; }
    }

    public override TextWrapping TextWrapping
    {
        get { return _textWrap; }
    }

    public override double LineHeight
    {
        get { return _lineHeight; }
    }

    public override double Indent
    {
        get { return _indent; }
    }

    public override TextMarkerProperties TextMarkerProperties
    {
        get { return null; }
    }

    public override double ParagraphIndent
    {
        get { return _paragraphIndent; }
    }

    private FlowDirection _flowDirection;
    private TextAlignment _textAlignment;
    private bool _firstLineInParagraph;
    private bool _alwaysCollapsible;
    private TextRunProperties _defaultTextRunProperties;
    private TextWrapping _textWrap;
    private double _indent;
    private double _paragraphIndent;
    private double _lineHeight;
}

Now TextSource implementation:

public class CustomTextSourceRun
{
    public string Text;
    public bool IsSuperscript;
    public bool IsEndParagraph;
    public int Length { get { return IsEndParagraph ? 1 : Text.Length; } }
}


class CustomTextSource : TextSource
{
    public List<CustomTextSourceRun> Runs = new List<CustomTextSourceRun>();

    public override TextRun GetTextRun(int textSourceCharacterIndex)
    {
        int pos = 0;
        foreach (var currentRun in Runs)
        {
            if (textSourceCharacterIndex < pos + currentRun.Length)
            {
                if (currentRun.IsEndParagraph)
                {
                    return new TextEndOfParagraph(1);
                }

                var props =
                    new CustomTextRunProperties(currentRun.IsSuperscript);

                return new TextCharacters(
                    currentRun.Text,
                    textSourceCharacterIndex - pos,
                    currentRun.Length - (textSourceCharacterIndex - pos),
                    props);


            }
            pos += currentRun.Length;
        }

        // Return an end-of-paragraph if no more text source.
        return new TextEndOfParagraph(1);
    }

    public override TextSpan<CultureSpecificCharacterBufferRange> GetPrecedingText(int textSourceCharacterIndexLimit)
    {
        throw new Exception("The method or operation is not implemented.");
    }

    public override int GetTextEffectCharacterIndexFromTextSourceCharacterIndex(int textSourceCharacterIndex)
    {
        throw new Exception("The method or operation is not implemented.");
    }

    public int Length
    {
        get
        {
            int r = 0;
            foreach (var currentRun in Runs)
            {
                r += currentRun.Length;
            }
            return r;
        }
    }
}

And all that's left to do is initialize out CustomTextSource and draw the text:

     var textStore = new CustomTextSource();
     textStore.Runs.Add(new CustomTextSourceRun() { Text = "3" });
     textStore.Runs.Add(new CustomTextSourceRun() { Text = "rd", IsSuperscript = true });
     textStore.Runs.Add(new CustomTextSourceRun() { IsEndParagraph = true });
     textStore.Runs.Add(new CustomTextSourceRun() { Text = "4" });
     textStore.Runs.Add(new CustomTextSourceRun() { Text = "th", IsSuperscript = true });

     int textStorePosition = 0;
     System.Windows.Point linePosition = new System.Windows.Point(0, 0); 

     textDest = new DrawingGroup();
     DrawingContext dc = textDest.Open();

     TextFormatter formatter = TextFormatter.Create();

     while (textStorePosition < textStore.Length)
     {
        using (TextLine myTextLine = formatter.FormatLine(
            textStore,
            textStorePosition,
            96*6,
            new GenericTextParagraphProperties(FlowDirection.LeftToRight,
                TextAlignment.Left,true,false, new CustomTextRunProperties(false), TextWrapping.Wrap,
                30,0), null))
        {
            myTextLine.Draw(dc, linePosition, InvertAxes.None);
            textStorePosition += myTextLine.Length;
            linePosition.Y += myTextLine.Height;
        }
     }

     dc.Close();

And that's it - we have superscript text in a drawing context.