Eliminate per-frame enum reflection/boxing in combo and property-grid enum rows

ImGui.Widgets/Combo.cs

@@ -20,14 +20,14 @@ public static partial class ImGuiWidgets
 	/// <returns>If a combo value was selected.</returns>
 	public static bool Combo<TEnum>(string label, ref TEnum selectedValue) where TEnum : Enum
 	{
-		Array possibleValues = Enum.GetValues(typeof(TEnum));
+		TEnum[] possibleValues = EnumCache<TEnum>.Values;
 		int currentIndex = Array.IndexOf(possibleValues, selectedValue);
-		string[] possibleValuesNames = Enum.GetNames(typeof(TEnum));
+		string[] possibleValuesNames = EnumCache<TEnum>.Names;
 		bool changed = ImGui.Combo(label, ref currentIndex, possibleValuesNames, possibleValuesNames.Length);
 		ImGuiProbes.MarkItem(label);
 		if (changed)
 		{
-			selectedValue = (TEnum)possibleValues.GetValue(currentIndex)!;
+			selectedValue = possibleValues[currentIndex];
 			return true;
 		}
 

ImGui.Widgets/EnumCache.cs

@@ -0,0 +1,9 @@
+// Copyright (c) 2023-2026 ktsu-dev contributors
+
+namespace ktsu.ImGui.Widgets;
+
+internal static class EnumCache<TEnum> where TEnum : Enum
+{
+	internal static readonly TEnum[] Values = (TEnum[])Enum.GetValues(typeof(TEnum));
+	internal static readonly string[] Names = Enum.GetNames(typeof(TEnum));
+}

ImGui.Widgets/EnumCombo.cs

@@ -39,17 +39,7 @@
 		/// </summary>
 		/// <typeparam name="T">The enum type to enumerate.</typeparam>
 		/// <returns>The display name of every declared member of <typeparamref name="T"/>.</returns>
-		internal static IReadOnlyList<string> Names<T>() where T : struct, Enum
-		{
-			T[] values = Enum.GetValues<T>();
-			List<string> names = new(values.Length);
-			foreach (T value in values)
-			{
-				names.Add(Hexa.NET.ImGui.Widgets.ComboEnumHelper<T>.GetName(value));
-			}
-
-			return names;
-		}
+		internal static IReadOnlyList<string> Names<T>() where T : struct, Enum => EnumComboNamesCache<T>.Names;
 
 		/// <summary>
 		/// Draws a combo box listing every member of an enum type.
@@ -59,10 +49,27 @@
 		/// <param name="value">The selected value, updated in place when a new member is chosen.</param>
 		/// <returns><see langword="true"/> if a new value was selected this frame.</returns>
 		/// <exception cref="ArgumentNullException"><paramref name="label"/> is <see langword="null"/>.</exception>
 		internal static bool Combo<T>(string label, ref T value) where T : struct, Enum
 		{
 			Ensure.NotNull(label);
 			return Hexa.NET.ImGui.Widgets.ComboEnumHelper<T>.Combo(label, ref value);
 		}
 	}
+
+	internal static class EnumComboNamesCache<T> where T : struct, Enum
+	{
+		internal static readonly string[] Names = BuildNames();
+
+		private static string[] BuildNames()
+		{
+			T[] values = EnumCache<T>.Values;
+			string[] names = new string[values.Length];
+			for (int index = 0; index < values.Length; index++)
+			{
+				names[index] = Hexa.NET.ImGui.Widgets.ComboEnumHelper<T>.GetName(values[index]);
+			}
+
+			return names;
+		}
+	}
 }

ImGui.Widgets/PropertyGridRows.cs

@@ -339,8 +339,8 @@ public bool Enum<TEnum>(string label, ref TEnum value) where TEnum : struct, Sys
 				return false;
 			}
 
-			string[] names = System.Enum.GetNames<TEnum>();
-			TEnum[] values = System.Enum.GetValues<TEnum>();
+			string[] names = EnumCache<TEnum>.Names;
+			TEnum[] values = EnumCache<TEnum>.Values;
 			int index = Array.IndexOf(values, value);
 
 			bool changed = ImGui.Combo(Hidden(label), ref index, names, names.Length);

tests/ImGui.Widgets.Tests/HexaWidgetTests.cs

@@ -140,6 +140,27 @@ public void EnumComboNames_FlagsEnum_ReturnsDeclaredMembersNotCombinations()
 		CollectionAssert.AreEqual(expected, names.ToArray());
 	}
 
+	[TestMethod]
+	public void EnumComboNames_RepeatedCalls_ReturnTheSameCachedInstance()
+	{
+		IReadOnlyList<string> first = ImGuiWidgets.EnumComboNames<PlainEnum>();
+		IReadOnlyList<string> second = ImGuiWidgets.EnumComboNames<PlainEnum>();
+
+		Assert.AreSame(first, second);
+	}
+
+	[TestMethod]
+	public void EnumCache_ReusesValuesAndNamesArraysPerEnumType()
+	{
+		PlainEnum[] valuesFirst = EnumCache<PlainEnum>.Values;
+		PlainEnum[] valuesSecond = EnumCache<PlainEnum>.Values;
+		string[] namesFirst = EnumCache<PlainEnum>.Names;
+		string[] namesSecond = EnumCache<PlainEnum>.Names;
+
+		Assert.AreSame(valuesFirst, valuesSecond);
+		Assert.AreSame(namesFirst, namesSecond);
+	}
+
 	[TestMethod]
 	public void EnumCombo_NullLabel_ThrowsBeforeTouchingImGui()
 	{