Merge pull request #2218 from AvaloniaUI/fixes/2191-tabcontrol-contentcontrolmixin

Register TabControl with ContentControlMixin.

samples/ControlCatalog/MainView.xaml

@@ -32,10 +32,10 @@
       <TabItem Header="ProgressBar"><pages:ProgressBarPage/></TabItem>
       <TabItem Header="RadioButton"><pages:RadioButtonPage/></TabItem>
       <TabItem Header="Slider"><pages:SliderPage/></TabItem>
+      <TabItem Header="TabControl"><pages:TabControlPage/></TabItem>
       <TabItem Header="TextBox"><pages:TextBoxPage/></TabItem>
       <TabItem Header="ToolTip"><pages:ToolTipPage/></TabItem>
       <TabItem Header="TreeView"><pages:TreeViewPage/></TabItem>
-      <TabItem Header="TabControl"><pages:TabControlPage/></TabItem>
       <TabItem Header="Viewbox"><pages:ViewboxPage/></TabItem>
     </TabControl>
   </Grid>

samples/ControlCatalog/SideBar.xaml

@@ -26,7 +26,7 @@
                             </ItemsPresenter>
                         </ScrollViewer>
                         <ContentPresenter
-                            Name="PART_Content"
+                            Name="PART_SelectedContentHost"
                             Margin="{TemplateBinding Padding}"                           
                             HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
                             VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"

src/Avalonia.Controls/TabControl.cs

@@ -2,6 +2,7 @@
 // Licensed under the MIT license. See licence.md file in the project root for full license information.
 
 using Avalonia.Controls.Generators;
+using Avalonia.Controls.Mixins;
 using Avalonia.Controls.Presenters;
 using Avalonia.Controls.Primitives;
 using Avalonia.Controls.Templates;
@@ -65,6 +66,10 @@ namespace Avalonia.Controls
             SelectionModeProperty.OverrideDefaultValue<TabControl>(SelectionMode.AlwaysSelected);
             ItemsPanelProperty.OverrideDefaultValue<TabControl>(DefaultPanel);
             AffectsMeasure<TabControl>(TabStripPlacementProperty);
+            ContentControlMixin.Attach<TabControl>(
+                SelectedContentProperty,
+                x => x.LogicalChildren,
+                "PART_SelectedContentHost");
         }
 
         /// <summary>
@@ -142,7 +147,7 @@ namespace Avalonia.Controls
 
             ItemsPresenterPart = e.NameScope.Get<ItemsPresenter>("PART_ItemsPresenter");
 
-            ContentPart = e.NameScope.Get<ContentPresenter>("PART_Content");
+            ContentPart = e.NameScope.Get<ContentPresenter>("PART_SelectedContentHost");
         }
 
         /// <inheritdoc/>

src/Avalonia.Themes.Default/TabControl.xaml

@@ -18,7 +18,7 @@
                             MemberSelector="{TemplateBinding MemberSelector}"                     >
                         </ItemsPresenter>
                         <ContentPresenter
-                            Name="PART_Content"
+                            Name="PART_SelectedContentHost"
                             Margin="{TemplateBinding Padding}"
                             HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
                             VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"

tests/Avalonia.Controls.UnitTests/TabControlTests.cs

@@ -267,26 +267,46 @@ namespace Avalonia.Controls.UnitTests
             Assert.Null(page.Content);
         }
 
+        [Fact]
+        public void DataTemplate_Created_Content_Should_Be_Logical_Child_After_ApplyTemplate()
+        {
+            TabControl target = new TabControl
+            {
+                Template = TabControlTemplate(),
+                ContentTemplate = new FuncDataTemplate<string>(x =>
+                    new TextBlock { Tag = "bar", Text = x }),
+                Items = new[] { "Foo" },
+            };
+
+            ApplyTemplate(target);
+            target.ContentPart.UpdateChild();
+
+            var content = Assert.IsType<TextBlock>(target.ContentPart.Child);
+            Assert.Equal("bar", content.Tag);
+            Assert.Same(target, content.GetLogicalParent());
+            Assert.Single(target.GetLogicalChildren(), content);
+        }
+
         private IControlTemplate TabControlTemplate()
         {
             return new FuncControlTemplate<TabControl>(parent =>
-
                 new StackPanel
                 {
-                    Children = {
-                                   new ItemsPresenter
-                                   {
-                                       Name = "PART_ItemsPresenter",
-                                       [!TabStrip.ItemsProperty] = parent[!TabControl.ItemsProperty],
-                                       [!TabStrip.ItemTemplateProperty] = parent[!TabControl.ItemTemplateProperty],
-                                   },
-                                   new ContentPresenter
-                                   {
-                                       Name = "PART_Content",
-                                       [!ContentPresenter.ContentProperty] = parent[!TabControl.SelectedContentProperty],
-                                       [!ContentPresenter.ContentTemplateProperty] = parent[!TabControl.SelectedContentTemplateProperty],
-                                   }
-                               }
+                    Children =
+                    {
+                        new ItemsPresenter
+                        {
+                            Name = "PART_ItemsPresenter",
+                            [!TabStrip.ItemsProperty] = parent[!TabControl.ItemsProperty],
+                            [!TabStrip.ItemTemplateProperty] = parent[!TabControl.ItemTemplateProperty],
+                        },
+                        new ContentPresenter
+                        {
+                            Name = "PART_SelectedContentHost",
+                            [!ContentPresenter.ContentProperty] = parent[!TabControl.SelectedContentProperty],
+                            [!ContentPresenter.ContentTemplateProperty] = parent[!TabControl.SelectedContentTemplateProperty],
+                        }
+                    }
                 });
         }