Barely tested Unity "Rich Text" substring tool

gistfile1.cs

	struct SubstringInfo
	{
		public int StartsAt;
		public string TagSuffix;

		public SubstringInfo(int startsAt, IEnumerable<string> tagSuffixChain)
		{
			StartsAt = startsAt;
			TagSuffix = string.Empty;
			foreach (var tagSuffix in tagSuffixChain)
				TagSuffix += tagSuffix;
		}
	}
	SubstringInfo[] textLengthFor;
	
// --------
	
	  // get text lengths
		var textLengths = new List<SubstringInfo>();
		var fullText = TextResource.text;
		var tagStack = new Stack<string>();
		int tentativeTagStartAt = -1;
		for (int i = 0; i < fullText.Length; i++)
		{
			char at = fullText[i];

			if (at == '<')
			{
				if (tentativeTagStartAt != -1)
					// wasn't a tag, add characters from there to here
					for (int j = tentativeTagStartAt; j < i; j++)
						textLengths.Add(new SubstringInfo(j, tagStack.ToArray()));

				tentativeTagStartAt = i;
			}
			else if (at == '>')
			{
				if (tentativeTagStartAt != -1)
				{
					var tag = fullText.Substring(tentativeTagStartAt, i - tentativeTagStartAt);
					if (tag.StartsWith("<color"))
						tagStack.Push("</color>");
					else if (tag.StartsWith("<size"))
						tagStack.Push("</size>");
					else if (tag.StartsWith("</color") || tag.StartsWith("</size"))
						tagStack.Pop(); // assume they'll match...
					else
					{
						// unrecognized tag, parse as text
						for (int j = tentativeTagStartAt; j < fullText.Length; j++)
							textLengths.Add(new SubstringInfo(j, tagStack.ToArray()));
					}

					tentativeTagStartAt = -1;
				}
				else
					textLengths.Add(new SubstringInfo(i, tagStack.ToArray()));
			}
			else
			{
				if (tentativeTagStartAt == -1)
					textLengths.Add(new SubstringInfo(i, tagStack.ToArray()));
			}
		}
		if (tentativeTagStartAt != -1)
			// wasn't a tag, add characters from there to here
			for (int j = tentativeTagStartAt; j < fullText.Length; j++)
				textLengths.Add(new SubstringInfo(j, tagStack.ToArray()));
		
// --------
		
		// usage
		guiText.text = fullText.Substring(0, textLengthFor[shownCharCount].StartsAt) + textLengthFor[shownCharCount].TagSuffix;