Avalonia/Windows/Perspex.Direct2D1/Media/FormattedTextImpl.cs

// -----------------------------------------------------------------------
// <copyright file="FormattedTextImpl.cs" company="Steven Kirk">
// Copyright 2014 MIT Licence. See licence.md for more information.
// </copyright>
// -----------------------------------------------------------------------

namespace Perspex.Direct2D1.Media
{
    using System;
    using System.Collections.Generic;
    using System.Linq;
    using Perspex.Media;
    using Perspex.Platform;
    using Splat;
    using DWrite = SharpDX.DirectWrite;

    public class FormattedTextImpl : IFormattedTextImpl
    {
        public FormattedTextImpl(
            string text,
            string fontFamily,
            double fontSize,
            FontStyle fontStyle,
            TextAlignment textAlignment,
            FontWeight fontWeight)
        {
            var factory = Locator.Current.GetService<DWrite.Factory>();

            var format = new DWrite.TextFormat(
                factory,
                fontFamily,
                (DWrite.FontWeight)fontWeight,
                (DWrite.FontStyle)fontStyle,
                (float)fontSize);

            this.TextLayout = new DWrite.TextLayout(
                factory,
                text ?? string.Empty,
                format,
                float.MaxValue,
                float.MaxValue);

            this.TextLayout.TextAlignment = textAlignment.ToDirect2D();
        }

        public Size Constraint
        {
            get
            {
                return new Size(this.TextLayout.MaxWidth, this.TextLayout.MaxHeight);
            }

            set
            {
                this.TextLayout.MaxWidth = (float)value.Width;
                this.TextLayout.MaxHeight = (float)value.Height;
            }
        }

        public DWrite.TextLayout TextLayout
        {
            get;
            private set;
        }

        public void Dispose()
        {
            this.TextLayout.Dispose();
        }

        public IEnumerable<FormattedTextLine> GetLines()
        {
            var result = this.TextLayout.GetLineMetrics();
            return from line in result select new FormattedTextLine(line.Length, line.Height);
        }

        public TextHitTestResult HitTestPoint(Point point)
        {
            SharpDX.Bool isTrailingHit;
            SharpDX.Bool isInside;

            var result = this.TextLayout.HitTestPoint(
                (float)point.X,
                (float)point.Y,
                out isTrailingHit,
                out isInside);

            return new TextHitTestResult
            {
                IsInside = isInside,
                TextPosition = result.TextPosition,
                IsTrailing = isTrailingHit,
            };
        }

        public Rect HitTestTextPosition(int index)
        {
            float x;
            float y;

            var result = this.TextLayout.HitTestTextPosition(
                index, 
                false, 
                out x, 
                out y);

            return new Rect(result.Left, result.Top, result.Width, result.Height);
        }

        public IEnumerable<Rect> HitTestTextRange(int index, int length, Point origin)
        {
            var result = this.TextLayout.HitTestTextRange(
                index, 
                length, 
                (float)origin.X, 
                (float)origin.Y);

            return result.Select(x => new Rect(x.Left, x.Top, x.Width, x.Height));
        }

        public Size Measure()
        {
            var metrics = this.TextLayout.Metrics;
            var width = metrics.WidthIncludingTrailingWhitespace;

            if (float.IsNaN(width))
            {
                width = metrics.Width;
            }

            return new Size(width, this.TextLayout.Metrics.Height);
        }

        public void SetForegroundBrush(Brush brush, int startIndex, int count)
        {
            this.TextLayout.SetDrawingEffect(
                new BrushWrapper(brush),
                new DWrite.TextRange(startIndex, count));
        }
    }
}