fix Duplicate DrawString

[7aGiven]

• I confirm that I am the author of this code and release it to the FNA project under the Ms-PL license. This contribution does not contain code from other sources, including code generated by a Large Language Model ("AI").

Try to unify string class and StringBuilder class.

Core code:

		internal interface IReadOnlyCharList
		{
			int Length { get; }
			char this[int index] { get; }
		}
		internal struct StringView : IReadOnlyCharList
		{
			private readonly string view;
			internal StringView(string view)
			{
				this.view = view;
			}
			public int Length
			{
				get
				{
					return view.Length;
				}
			}
			public char this[int index]
			{
				get
				{
					return view[index];
				}
			}
		}
		internal struct StringBuilderView : IReadOnlyCharList
		{
			private readonly StringBuilder view;
			internal StringBuilderView(StringBuilder view)
			{
				this.view = view;
			}
			public int Length
			{
				get
				{
					return view.Length;
				}
			}
			public char this[int index]
			{
				get
				{
					return view[index];
				}
			}
		}

[flibitijibibo]

Mostly focused on style for this pass but this seems okay; since the reader is a struct I don't anticipate additional memory pressure, but I'll ask others to see if this has any measurable effect on performance.

[kg]

Making this a struct is pointless since you're going to box it anyway, it would be better as a sealed class to read how it's going to behave

[7aGiven]

Thank you, I follow your suggestion that use generic method instead of interface argument. So no boxing now.

[kg]

ref just adds overhead here because the argument is of a boxed type (an interface). If you had MeasureString<T>(ref T text) where T : IReadOnlyCharList then ref would make sense and you could avoid boxing.

[7aGiven]

Thank you, I have not get the knowledge before. I know it now from https://giannisakritidis.com/blog/Avoid-Struct-Boxing/

[kg]

As mentioned in another comment, by construction this boxes the StringBuilderView to store it in a reference-typed (IReadOnlyCharList) local, then passes a reference to the reference, which is unnecessary. Either make DrawString generic so you can pass structs into it by-ref or drop the ref here.

[7aGiven]

Thank you, I follow your suggestion that use generic method instead of interface argument. So no boxing now.

[kg]

Thanks for doing this refactoring. Have you tested it using VS's memory profiler to see whether it allocates? It's possible the modern .NET JIT is smart enough to optimize out some of the boxing here but I would expect it to box each adapter instance.

[7aGiven]

Thanks for doing this refactoring. Have you tested it using VS's memory profiler to see whether it allocates? It's possible the modern .NET JIT is smart enough to optimize out some of the boxing here but I would expect it to box each adapter instance.

I find that there is box instruction in dotnet IL. So I think it must be fix regardless of whether the JIT can optimize it.

[kg]

I can't easily test this locally because I don't have any spritefont-based games lying around but the new code looks good.