From 1909d7a77804d740b79874fb663b02b22edac49c Mon Sep 17 00:00:00 2001
From: Dariusz Komosinski <darek.komosinski@gmail.com>
Date: Thu, 5 Mar 2020 00:18:46 +0100
Subject: [PATCH 1/2] Avoid IAffectsRender subscribe attempts on values that
 can't implement it.

---
 .../AvaloniaPropertyExtensions.cs             | 27 +++++++++++++++++++
 src/Avalonia.Visuals/Media/Brush.cs           |  4 +--
 src/Avalonia.Visuals/Media/Pen.cs             | 20 +++++++++++---
 src/Avalonia.Visuals/Visual.cs                | 21 ++++++++++++---
 4 files changed, 64 insertions(+), 8 deletions(-)
 create mode 100644 src/Avalonia.Visuals/AvaloniaPropertyExtensions.cs

diff --git a/src/Avalonia.Visuals/AvaloniaPropertyExtensions.cs b/src/Avalonia.Visuals/AvaloniaPropertyExtensions.cs
new file mode 100644
index 0000000000..6aaa224b00
--- /dev/null
+++ b/src/Avalonia.Visuals/AvaloniaPropertyExtensions.cs
@@ -0,0 +1,27 @@
+using Avalonia.Media;
+
+#nullable enable
+
+namespace Avalonia
+{
+    /// <summary>
+    /// Extensions for <see cref="AvaloniaProperty"/>.
+    /// </summary>
+    public static class AvaloniaPropertyExtensions
+    {
+        /// <summary>
+        /// Checks if values of given property can affect rendering (via <see cref="IAffectsRender"/>).
+        /// </summary>
+        /// <param name="property">Property to check.</param>
+        public static bool CanValueAffectRender(this AvaloniaProperty property)
+        {
+            var propertyType = property.PropertyType;
+
+            // Only case that we are sure that property value CAN'T affect render are sealed types that don't implement
+            // the interface.
+            var cannotAffectRender = propertyType.IsSealed && !typeof(IAffectsRender).IsAssignableFrom(propertyType);
+
+            return !cannotAffectRender;
+        }
+    }
+}
diff --git a/src/Avalonia.Visuals/Media/Brush.cs b/src/Avalonia.Visuals/Media/Brush.cs
index f36cd88537..0d08f92685 100644
--- a/src/Avalonia.Visuals/Media/Brush.cs
+++ b/src/Avalonia.Visuals/Media/Brush.cs
@@ -69,14 +69,14 @@ namespace Avalonia.Media
         protected static void AffectsRender<T>(params AvaloniaProperty[] properties)
             where T : Brush
         {
-            void Invalidate(AvaloniaPropertyChangedEventArgs e)
+            static void Invalidate(AvaloniaPropertyChangedEventArgs e)
             {
                 (e.Sender as T)?.RaiseInvalidated(EventArgs.Empty);
             }
 
             foreach (var property in properties)
             {
-                property.Changed.Subscribe(Invalidate);
+                property.Changed.Subscribe(e => Invalidate(e));
             }
         }
 
diff --git a/src/Avalonia.Visuals/Media/Pen.cs b/src/Avalonia.Visuals/Media/Pen.cs
index b88fae28ff..8ab2b11331 100644
--- a/src/Avalonia.Visuals/Media/Pen.cs
+++ b/src/Avalonia.Visuals/Media/Pen.cs
@@ -2,7 +2,6 @@
 // Licensed under the MIT license. See licence.md file in the project root for full license information.
 
 using System;
-using System.Collections.Generic;
 using Avalonia.Media.Immutable;
 using Avalonia.Utilities;
 
@@ -197,7 +196,15 @@ namespace Avalonia.Media
         protected static void AffectsRender<T>(params AvaloniaProperty[] properties)
             where T : Pen
         {
-            void Invalidate(AvaloniaPropertyChangedEventArgs e)
+            static void Invalidate(AvaloniaPropertyChangedEventArgs e)
+            {
+                if (e.Sender is T sender)
+                {
+                    sender.RaiseInvalidated(EventArgs.Empty);
+                }
+            }
+
+            static void InvalidateAndSubscribe(AvaloniaPropertyChangedEventArgs e)
             {
                 if (e.Sender is T sender)
                 {
@@ -223,7 +230,14 @@ namespace Avalonia.Media
 
             foreach (var property in properties)
             {
-                property.Changed.Subscribe(Invalidate);
+                if (property.CanValueAffectRender())
+                {
+                    property.Changed.Subscribe(e => InvalidateAndSubscribe(e));
+                }
+                else
+                {
+                    property.Changed.Subscribe(e => Invalidate(e));
+                }
             }
         }
 
diff --git a/src/Avalonia.Visuals/Visual.cs b/src/Avalonia.Visuals/Visual.cs
index bd2ab6e614..018af060c1 100644
--- a/src/Avalonia.Visuals/Visual.cs
+++ b/src/Avalonia.Visuals/Visual.cs
@@ -336,7 +336,15 @@ namespace Avalonia
         protected static void AffectsRender<T>(params AvaloniaProperty[] properties)
             where T : Visual
         {
-            void Invalidate(AvaloniaPropertyChangedEventArgs e)
+            static void Invalidate(AvaloniaPropertyChangedEventArgs e)
+            {
+                if (e.Sender is T sender)
+                {
+                    sender.InvalidateVisual();
+                }
+            }
+
+            static void InvalidateAndSubscribe(AvaloniaPropertyChangedEventArgs e)
             {
                 if (e.Sender is T sender)
                 {
@@ -347,7 +355,7 @@ namespace Avalonia
 
                     if (e.NewValue is IAffectsRender newValue)
                     {
-                        WeakEventHandlerManager.Subscribe<IAffectsRender, EventArgs, T>(newValue, nameof(newValue.Invalidated), sender.AffectsRenderInvalidated);                        
+                        WeakEventHandlerManager.Subscribe<IAffectsRender, EventArgs, T>(newValue, nameof(newValue.Invalidated), sender.AffectsRenderInvalidated);
                     }
 
                     sender.InvalidateVisual();
@@ -356,7 +364,14 @@ namespace Avalonia
 
             foreach (var property in properties)
             {
-                property.Changed.Subscribe(Invalidate);
+                if (property.CanValueAffectRender())
+                {
+                    property.Changed.Subscribe(e => InvalidateAndSubscribe(e));
+                }
+                else
+                {
+                    property.Changed.Subscribe(e => Invalidate(e));
+                }
             }
         }
 

From 1027168c61e7b5342620941889abbc25d502fa9b Mon Sep 17 00:00:00 2001
From: Dariusz Komosinski <darek.komosinski@gmail.com>
Date: Thu, 5 Mar 2020 00:29:37 +0100
Subject: [PATCH 2/2] Remove omen of bad performance.

---
 src/Avalonia.Visuals/Visual.cs | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/Avalonia.Visuals/Visual.cs b/src/Avalonia.Visuals/Visual.cs
index 018af060c1..d9032cfa3e 100644
--- a/src/Avalonia.Visuals/Visual.cs
+++ b/src/Avalonia.Visuals/Visual.cs
@@ -3,7 +3,6 @@
 
 using System;
 using System.Collections.Specialized;
-using System.Linq;
 using Avalonia.Collections;
 using Avalonia.Data;
 using Avalonia.Logging;