Report correct root in logical tree attach/detach.

Fixes #1192.

src/Avalonia.Controls/Control.cs

@@ -773,11 +773,9 @@ namespace Avalonia.Controls
         {
             while (e != null)
             {
-                var root = e as IStyleRoot;
-
-                if (root != null && root.StylingParent == null)
+                if (e is IRenderRoot root)
                 {
-                    return root;
+                    return root as IStyleRoot;
                 }
 
                 e = e.StylingParent;

tests/Avalonia.Controls.UnitTests/ControlTests.cs

@@ -123,7 +123,26 @@ namespace Avalonia.Controls.UnitTests
         }
 
         [Fact]
-        public void DetachedToLogicalParent_Should_Be_Called_When_Removed_From_Tree()
+        public void AttachedToLogicalParent_Should_Not_Be_Called_With_GlobalStyles_As_Root()
+        {
+            var globalStyles = Mock.Of<IGlobalStyles>();
+            var root = new TestRoot { StylingParent = globalStyles };
+            var child = new Border();
+            var raised = false;
+
+            child.AttachedToLogicalTree += (s, e) =>
+            {
+                Assert.Equal(root, e.Root);
+                raised = true;
+            };
+
+            root.Child = child;
+
+            Assert.True(raised);
+        }
+
+        [Fact]
+        public void DetachedFromLogicalParent_Should_Be_Called_When_Removed_From_Tree()
         {
             var root = new TestRoot();
             var parent = new Border();
@@ -148,6 +167,26 @@ namespace Avalonia.Controls.UnitTests
             Assert.True(grandchildRaised);
         }
 
+        [Fact]
+        public void DetachedFromLogicalParent_Should_Not_Be_Called_With_GlobalStyles_As_Root()
+        {
+            var globalStyles = Mock.Of<IGlobalStyles>();
+            var root = new TestRoot { StylingParent = globalStyles };
+            var child = new Border();
+            var raised = false;
+
+            child.DetachedFromLogicalTree += (s, e) =>
+            {
+                Assert.Equal(root, e.Root);
+                raised = true;
+            };
+
+            root.Child = child;
+            root.Child = null;
+
+            Assert.True(raised);
+        }
+
         [Fact]
         public void Adding_Tree_To_IStyleRoot_Should_Style_Controls()
         {

tests/Avalonia.Controls.UnitTests/Presenters/ContentPresenterTests_Standalone.cs

@@ -12,6 +12,7 @@ using Moq;
 using System;
 using System.Linq;
 using Xunit;
+using Avalonia.Rendering;
 
 namespace Avalonia.Controls.UnitTests.Presenters
 {
@@ -56,6 +57,7 @@ namespace Avalonia.Controls.UnitTests.Presenters
 
             var parentMock = new Mock<Control>();
             parentMock.As<IContentPresenterHost>();
+            parentMock.As<IRenderRoot>();
             parentMock.As<IStyleRoot>();
 
             (target as ISetLogicalParent).SetParent(parentMock.Object);
@@ -100,6 +102,7 @@ namespace Avalonia.Controls.UnitTests.Presenters
             };
 
             var parentMock = new Mock<Control>();
+            parentMock.As<IRenderRoot>();
             parentMock.As<IStyleRoot>();
             parentMock.As<ILogical>().SetupGet(l => l.IsAttachedToLogicalTree).Returns(true);
 
@@ -144,6 +147,7 @@ namespace Avalonia.Controls.UnitTests.Presenters
 
             var parentMock = new Mock<Control>();
             parentMock.As<IContentPresenterHost>();
+            parentMock.As<IRenderRoot>();
             parentMock.As<IStyleRoot>();
 
             (target as ISetLogicalParent).SetParent(parentMock.Object);