Add Transformlist.

Classes/TransformList.cs

@@ -0,0 +1,33 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace OtterGui.Classes;
+
+/// <summary>
+/// A IReadOnlyList based on any other IReadOnlyList that applies a transforming step before fetching.
+/// </summary>
+public readonly struct TransformList<TIn, TOut> : IReadOnlyList<TOut>
+{
+ private readonly IReadOnlyList<TIn> _list;
+ private readonly Func<TIn, TOut> _transform;
+
+ public TransformList(IReadOnlyList<TIn> items, Func<TIn, TOut> transform)
+ {
+ _list = items;
+ _transform = transform;
+ }
+
+ public IEnumerator<TOut> GetEnumerator()
+ => _list.Select(_transform).GetEnumerator();
+
+ IEnumerator IEnumerable.GetEnumerator()
+ => GetEnumerator();
+
+ public int Count
+ => _list.Count;
+
+ public TOut this[int index]
+ => _transform(_list[index]);
+}