Indentation in WPF TextFormatter - wpf

Question

I'm making a WPF text-editor using TextFormatter. I need to indent some paragraphs, so I'm using the Indent property from the TextParagraphProperties class.
This works great in this scenario:
Regular text without any
indentation.
This paragraph has a uniform
indentation so everything is
ok.
But I also need this:
John: This paragraph has a
diferent indentation
in the first line.
Joe: So I don't know how
to make this happen.
I found the ParagraphIndent and FirstLineInParagraph properties, but I don't know how they works, or if then would be usefull.
Thanks in advance!!
Jose

Answer 1

Jose --
Hopefully this code skeleton will help... I assume that you started from the Advanced Text Formatting project on MSDN, which, sadly is not very advanced. Here is a code fragment you can introduce to MainWindow.Xaml.cs:
TextParagraphProperties textParagraphProperties = new GenericTextParagraphProperties(TextAlignment.Left,
false);
TextRunCache textRunCache = new TextRunCache();
// By default, this is the first line of a paragrph
bool firstLine = true;
while (textStorePosition < _textStore.Length)
{
// Create a textline from the text store using the TextFormatter object.
TextLine myTextLine = formatter.FormatLine(
_textStore,
textStorePosition,
96 * 6,
// ProxyTextParagraphProperties will return a different value for the Indent property,
// depending on whether firstLine is true or not.
new ProxyTextParagraphProperties(textParagraphProperties, firstLine),
lastLineBreak,
textRunCache);
// Draw the formatted text into the drawing context.
Debug.WriteLine("linePosition:" + linePosition);
myTextLine.Draw(dc, linePosition, InvertAxes.None);
// Update the index position in the text store.
textStorePosition += myTextLine.Length;
// Update the line position coordinate for the displayed line.
linePosition.Y += myTextLine.Height;
// Figure out if the next line is the first line of a paragraph
var textRunSpans = myTextLine.GetTextRunSpans();
firstLine = (textRunSpans.Count > 0) && (textRunSpans[textRunSpans.Count - 1].Value is TextEndOfParagraph);
lastLineBreak = myTextLine.GetTextLineBreak();
}
You'll need to create the class ProxyTextParagraphProperties, which descends from TextParagraphProperties. Here's a snip of what I did to test this:
class ProxyTextParagraphProperties : TextParagraphProperties
{
private readonly TextParagraphProperties _paragraphProperties;
private readonly bool _firstLineInParagraph;
public ProxyTextParagraphProperties(TextParagraphProperties textParagraphProperties, bool firstLineInParagraph)
{
_paragraphProperties = textParagraphProperties;
_firstLineInParagraph = firstLineInParagraph;
}
public override FlowDirection FlowDirection
{
get { return _paragraphProperties.FlowDirection; }
}
// implement the same as above for all the other properties...
// But we need to handle this one specially...
public override double Indent
{
get
{
return _firstLineInParagraph ? _paragraphProperties.Indent : 0;
}
}
}