From 9078ca7dc8b2512322e5a2b26e91c2ca8348f9e1 Mon Sep 17 00:00:00 2001
From: Jan-Peter Zurek <j.zurek@swiftconsult.de>
Date: Wed, 26 Jan 2022 14:46:54 +0100
Subject: [PATCH] Fix Rotate3DTransform for DeferredRenderer.

---
 .../Avalonia.Build.Tasks.csproj                 |  1 +
 src/Avalonia.Visuals/Matrix.cs                  |  2 +-
 src/Avalonia.Visuals/Point.cs                   | 17 +++++++++++++++++
 3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/src/Avalonia.Build.Tasks/Avalonia.Build.Tasks.csproj b/src/Avalonia.Build.Tasks/Avalonia.Build.Tasks.csproj
index e864ea2007..7e4272f5d2 100644
--- a/src/Avalonia.Build.Tasks/Avalonia.Build.Tasks.csproj
+++ b/src/Avalonia.Build.Tasks/Avalonia.Build.Tasks.csproj
@@ -94,5 +94,6 @@
       <Compile Remove="../Markup/Avalonia.Markup.Xaml.Loader\xamlil.github\src\XamlX\IL\SreTypeSystem.cs" />
       <PackageReference Include="Mono.Cecil" Version="0.11.2" />
       <PackageReference Include="Microsoft.Build.Framework" Version="15.1.548" PrivateAssets="All" />
+      <PackageReference Include="System.Numerics.Vectors" Version="4.5.0" />
     </ItemGroup>
 </Project>
diff --git a/src/Avalonia.Visuals/Matrix.cs b/src/Avalonia.Visuals/Matrix.cs
index 4326dc3670..38d0508ffb 100644
--- a/src/Avalonia.Visuals/Matrix.cs
+++ b/src/Avalonia.Visuals/Matrix.cs
@@ -357,7 +357,7 @@ namespace Avalonia
         /// <summary>
         ///  Determines if the current matrix contains perspective (non-affine) transforms (true) or only (affine) transforms that could be mapped into an 2x3 matrix (false).
         /// </summary>
-        private bool ContainsPerspective()
+        public bool ContainsPerspective()
         {
 
             // ReSharper disable CompareOfFloatsByEqualityOperator
diff --git a/src/Avalonia.Visuals/Point.cs b/src/Avalonia.Visuals/Point.cs
index 67e7d71fbc..473de8e501 100644
--- a/src/Avalonia.Visuals/Point.cs
+++ b/src/Avalonia.Visuals/Point.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Globalization;
+using System.Numerics;
 #if !BUILDTASK
 using Avalonia.Animation.Animators;
 #endif
@@ -244,6 +245,22 @@ namespace Avalonia
         /// <returns>The transformed point.</returns>
         public Point Transform(Matrix transform)
         {
+            if (transform.ContainsPerspective())
+            {
+                var m44 = new Matrix4x4(
+                    (float)transform.M11, (float)transform.M12, (float)transform.M13, 0,
+                    (float)transform.M21, (float)transform.M22, (float)transform.M23, 0,
+                    (float)transform.M31, (float)transform.M32, (float)transform.M33, 0,
+                    0, 0, 0, 1
+                );
+            
+                var vector = new Vector3((float)X, (float)Y, 1);
+                var transformedVector = Vector3.Transform(vector, m44);
+                var z = 1 / transformedVector.Z;
+            
+                return new Point(transformedVector.X * z, transformedVector.Y * z);
+            }
+            
             var x = X;
             var y = Y;
             var xadd = y * transform.M21 + transform.M31;