perf: Cache self style key to avoid Type.ToString invocations

Author: jeromelaban

src/Uno.UI/UI/Xaml/DependencyObjectExtensions.cs

@@ -90,8 +90,8 @@ internal static void StoreDisableHardReferences(this IDependencyObjectStoreProvi
 		/// Gets the implicit style for the current object
 		/// </summary>
 		[global::System.ComponentModel.EditorBrowsableAttribute(global::System.ComponentModel.EditorBrowsableState.Never)]
-		internal static Style StoreGetImplicitStyle(this IDependencyObjectStoreProvider provider)
-			=> provider.Store.GetImplicitStyle();
+		internal static Style StoreGetImplicitStyle(this IDependencyObjectStoreProvider provider, in SpecializedResourceDictionary.ResourceKey styleKey)
+			=> provider.Store.GetImplicitStyle(styleKey);
 
 		internal static IEnumerable<object> GetParents(this object dependencyObject)
 		{

src/Uno.UI/UI/Xaml/DependencyObjectStore.cs

@@ -1246,11 +1246,11 @@ private IEnumerable<ResourceDictionary> GetResourceDictionaries(bool includeAppR
 		/// <summary>
 		/// Retrieve the implicit Style for <see cref="ActualInstance"/> by walking the visual tree.
 		/// </summary>
-		internal Style? GetImplicitStyle()
+		internal Style? GetImplicitStyle(in SpecializedResourceDictionary.ResourceKey styleKey)
 		{
 			foreach (var dict in GetResourceDictionaries(includeAppResources: true))
 			{
-				if (dict.TryGetValue(_originalObjectType, out var style, shouldCheckSystem: false))
+				if (dict.TryGetValue(styleKey, out var style, shouldCheckSystem: false))
 				{
 					return style as Style;
 				}

src/Uno.UI/UI/Xaml/FrameworkElement.cs

@@ -60,11 +60,17 @@ public static class TraceProvider
 
 		private bool _defaultStyleApplied = false;
 		private protected bool IsDefaultStyleApplied => _defaultStyleApplied;
+
 		/// <summary>
 		/// The current user-determined 'active Style'. This will either be the explicitly-set Style, if there is one, or otherwise the resolved implicit Style (either in the view hierarchy or in Application.Resources).
 		/// </summary>
 		private Style _activeStyle = null;
 
+		/// <summary>
+		/// Cache for the current type key for faster implicit style lookup
+		/// </summary>
+		private SpecializedResourceDictionary.ResourceKey _thisTypeResourceKey;
+
 		/// <summary>
 		/// Sets whether constraint-based optimizations are used to limit redrawing of the entire visual tree on Android. This can be
 		/// globally set to false if it is causing visual errors (eg views not updating properly). Note: this can still be overridden by
@@ -383,7 +389,20 @@ private void UpdateActiveStyle()
 			}
 		}
 
-		private Style ResolveImplicitStyle() => this.StoreGetImplicitStyle();
+		private SpecializedResourceDictionary.ResourceKey ThisTypeResourceKey
+		{
+			get
+			{
+				if(_thisTypeResourceKey.IsEmpty)
+				{
+					_thisTypeResourceKey = this.GetType();
+				}
+
+				return _thisTypeResourceKey;
+			}
+		}
+
+		private Style ResolveImplicitStyle() => this.StoreGetImplicitStyle(ThisTypeResourceKey);
 
 		#region Requested theme dependency property