Shaker/Veldrid/FontStashSharp/RichText/TextChunk.cs

using System;
using System.Collections.Generic;

#if MONOGAME || FNA
using Microsoft.Xna.Framework;
#elif STRIDE
using Stride.Core.Mathematics;
#else
using System.Drawing;
using System.Numerics;
using Color = Veldrid.RgbaFloat;
#endif

namespace FontStashSharp.RichText
{
	public class TextChunk : BaseChunk
	{
		protected string _text;
		protected readonly SpriteFontBase _font;
		protected Point _size;

		public List<TextChunkGlyph> Glyphs { get; } = new List<TextChunkGlyph>();

		public int Count { get { return _text.Length(); } }
		public string Text { get { return _text; } }
		public override Point Size { get { return _size; } }

		public SpriteFontBase Font => _font;
		public TextStyle Style { get; set; }

		public TextChunk(SpriteFontBase font, string text, Point size, Point? startPos)
		{
			if (font == null)
			{
				throw new ArgumentNullException("font");
			}

			_font = font;
			_text = text;
			_size = size;

			if (startPos != null)
			{
				CalculateGlyphs(startPos.Value);
			}
		}

		private void CalculateGlyphs(Point startPos)
		{
			if (string.IsNullOrEmpty(_text))
			{
				return;
			}

			var glyphs = _font.GetGlyphs(_text, Vector2.Zero);

			Glyphs.Clear();
			for (var i = 0; i < glyphs.Count; ++i)
			{
				var glyph = glyphs[i];
				var bounds = glyph.Bounds;
				bounds.Offset(startPos);
				Glyphs.Add(new TextChunkGlyph
				{
					TextChunk = this,
					LineTop = startPos.Y,
					Index = glyph.Index,
					Codepoint = glyph.Codepoint,
					Bounds = bounds,
					XAdvance = glyph.XAdvance
				});
			}
		}

		public TextChunkGlyph? GetGlyphInfoByIndex(int index)
		{
			if (string.IsNullOrEmpty(_text) || index < 0 || index >= _text.Length)
			{
				return null;
			}

			return Glyphs[index];
		}

		public int? GetGlyphIndexByX(int x)
		{
			if (Glyphs.Count == 0 || x < 0)
			{
				return null;
			}

			var i = 0;
			for (; i < Glyphs.Count; ++i)
			{
				var glyph = Glyphs[i];
				var width = glyph.XAdvance;
				var right = glyph.Bounds.X + width;

				if (glyph.Bounds.X <= x && x <= right)
				{
					if (x - glyph.Bounds.X >= width / 2)
					{
						++i;
					}

					break;
				}
			}

			if (i - 1 >= 0 && i - 1 < Glyphs.Count && Glyphs[i - 1].Codepoint == '\n')
			{
				--i;
			}

			return i;
		}

		public override void Draw(FSRenderContext context, Vector2 position, Color color)
		{
			context.DrawText(Text, Font, position, color, Style);
		}
	}
}