Common.Wpf/HtmlTextBlock/TextFragment.cs

using System.Globalization;
using System.Windows;
using System.Windows.Media;

namespace Common.Wpf.HtmlTextBlock
{
    public class TextFragment
    {
        private readonly HtmlTextBlock _parent;

        public Brush Color { get; set; }
        public FontStyle Style { get; set; }
        public FontWeight Weight { get; set; }
        public double Size { get; set; }
        public string Text { get; set; }
        public bool Underline { get; set; }

        private Typeface _typeface;
        public Typeface Typeface
        {
            get { return _typeface ?? (_typeface = new Typeface(_parent.FontFamily, Style, Weight, _parent.FontStretch)); }
        }

        private FormattedText _formattedText;
        public FormattedText FormattedText
        {
            get
            {
                if (_formattedText == null)
                {
                    string measureText = (string.IsNullOrEmpty(Text) ? " " : Text);

                    _formattedText = new FormattedText(measureText, CultureInfo.CurrentUICulture, FlowDirection.LeftToRight, Typeface, Size, Color);

                    TextDecorationCollection textDecorationCollection = new TextDecorationCollection();

                    if (Underline)
                    {
                        TextDecoration underlineDecoration = new TextDecoration { PenThicknessUnit = TextDecorationUnit.FontRecommended };

                        textDecorationCollection.Add(underlineDecoration);
                    }

                    _formattedText.SetTextDecorations(textDecorationCollection);
                }

                return _formattedText;
            }
        }

        public TextFragment(HtmlTextBlock parent)
        {
            _parent = parent;

            Color = _parent.Foreground;
            Style = _parent.FontStyle;
            Weight = _parent.FontWeight;
            Size = _parent.FontSize;
            Text = string.Empty;
            Underline = false;
        }
    }
}