Implement GetTemplateDescendants (#21245)

* Implement GetTemplateDescendants

* Use GetTemplateDescendants in Avalonia.Controls

* Use GetTemplateDescendants in tests

* Fix obsolete warnings

src/Avalonia.Controls/Primitives/LightDismissOverlayLayer.cs

@@ -34,7 +34,7 @@ namespace Avalonia.Controls.Primitives
 
             if (visual is TopLevel topLevel)
             {
-                manager = topLevel.GetTemplateChildren()
+                manager = topLevel.GetTemplateDescendants()
                     .OfType<VisualLayerManager>()
                     .FirstOrDefault();
             }

src/Avalonia.Controls/Primitives/TemplatedControl.cs

@@ -317,7 +317,7 @@ namespace Avalonia.Controls.Primitives
             {
                 if (VisualChildren.Count > 0)
                 {
-                    foreach (var child in this.GetTemplateChildren())
+                    foreach (var child in this.GetTemplateDescendants())
                     {
                         child.TemplatedParent = null;
                         ((ISetLogicalParent)child).SetParent(null);
@@ -350,11 +350,11 @@ namespace Avalonia.Controls.Primitives
         /// <inheritdoc/>
         protected override Control GetTemplateFocusTarget()
         {
-            foreach (Control child in this.GetTemplateChildren())
+            foreach (var child in this.GetTemplateDescendants())
             {
-                if (GetIsTemplateFocusTarget(child))
+                if (child is Control control && GetIsTemplateFocusTarget(control))
                 {
-                    return child;
+                    return control;
                 }
             }
 

src/Avalonia.Controls/Templates/TemplateExtensions.cs

@@ -1,26 +1,47 @@
 using System;
 using System.Collections.Generic;
-using System.Linq;
-using Avalonia.Controls;
 using Avalonia.Controls.Primitives;
-using Avalonia.Styling;
 using Avalonia.VisualTree;
 
 namespace Avalonia.Controls.Templates
 {
+    /// <summary>
+    /// Contains extension methods for <see cref="TemplatedControl"/>.
+    /// </summary>
     public static class TemplateExtensions
     {
+        /// <summary>
+        /// Gets the list of all control descendants that are part of the template of a <see cref="TemplatedControl"/>,
+        /// i.e. their <see cref="StyledElement.TemplatedParent"/> is <paramref name="control"/>.
+        /// </summary>
+        /// <param name="control">The control whose descendants will be returned.</param>
+        /// <returns>An enumeration of <see cref="Control"/> objects.</returns>
+        [Obsolete($"Use {nameof(GetTemplateDescendants)}")]
         public static IEnumerable<Control> GetTemplateChildren(this TemplatedControl control)
         {
-            foreach (Control child in GetTemplateChildren(control, control))
+            foreach (var child in control.GetTemplateDescendants())
             {
-                yield return child;
+                if (child is Control childControl)
+                {
+                    yield return childControl;
+                }
             }
         }
 
-        private static IEnumerable<Control> GetTemplateChildren(Control control, TemplatedControl templatedParent)
+        /// <summary>
+        /// Gets the list of all visual descendants that are part of the template of a <see cref="TemplatedControl"/>,
+        /// i.e. their <see cref="StyledElement.TemplatedParent"/> is <paramref name="control"/>.
+        /// </summary>
+        /// <param name="control">The control whose descendants will be returned.</param>
+        /// <returns>An enumeration of <see cref="Visual"/> objects.</returns>
+        public static IEnumerable<Visual> GetTemplateDescendants(this TemplatedControl control)
+        {
+            return GetTemplateDescendants(control, control);
+        }
+
+        private static IEnumerable<Visual> GetTemplateDescendants(Visual control, TemplatedControl templatedParent)
         {
-            foreach (Control child in control.GetVisualChildren())
+            foreach (var child in control.GetVisualChildren())
             {
                 var childTemplatedParent = child.TemplatedParent;
 
@@ -31,7 +52,7 @@ namespace Avalonia.Controls.Templates
 
                 if (childTemplatedParent != null)
                 {
-                    foreach (var descendant in GetTemplateChildren(child, templatedParent))
+                    foreach (var descendant in GetTemplateDescendants(child, templatedParent))
                     {
                         yield return descendant;
                     }

tests/Avalonia.Base.UnitTests/Layout/FullLayoutTests.cs

@@ -86,8 +86,8 @@ namespace Avalonia.Base.UnitTests.Layout
                 Assert.Equal(new Point(300, 200), Position(scrollViewer));
                 Assert.Equal(new Size(400, 400), textBlock.Bounds.Size);
 
-                var scrollBars = scrollViewer.GetTemplateChildren().OfType<ScrollBar>().ToList();
-                var presenters = scrollViewer.GetTemplateChildren().OfType<ScrollContentPresenter>().ToList();
+                var scrollBars = scrollViewer.GetTemplateDescendants().OfType<ScrollBar>().ToList();
+                var presenters = scrollViewer.GetTemplateDescendants().OfType<ScrollContentPresenter>().ToList();
 
                 Assert.Equal(2, scrollBars.Count);
                 Assert.Single(presenters);

tests/Avalonia.Controls.UnitTests/AutoCompleteBoxTests.cs

@@ -1235,7 +1235,7 @@ namespace Avalonia.Controls.UnitTests
         }
         private TextBox GetTextBox(AutoCompleteBox control)
         {
-            return control.GetTemplateChildren()
+            return control.GetTemplateDescendants()
                           .OfType<TextBox>()
                           .First();
         }

tests/Avalonia.Controls.UnitTests/CalendarDatePickerTests.cs

@@ -155,7 +155,7 @@ namespace Avalonia.Controls.UnitTests
 
         private TextBox GetTextBox(CalendarDatePicker control)
         {
-            return control.GetTemplateChildren()
+            return control.GetTemplateDescendants()
                 .OfType<TextBox>()
                 .First();
         }

tests/Avalonia.Controls.UnitTests/ComboBoxTests.cs

@@ -834,7 +834,7 @@ namespace Avalonia.Controls.UnitTests
             target.ApplyTemplate();
             target.Presenter!.ApplyTemplate();
 
-            var containerPanel = target.GetTemplateChildren().OfType<Panel>().FirstOrDefault(x => x.Name == "container");
+            var containerPanel = target.GetTemplateDescendants().OfType<Panel>().FirstOrDefault(x => x.Name == "container");
             var editableTextBox = containerPanel?.GetVisualDescendants().OfType<TextBox>().FirstOrDefault(x => x.Name == "PART_EditableTextBox");
             var popup = containerPanel?.GetVisualDescendants().OfType<Popup>().FirstOrDefault(x => x.Name == "PART_Popup");
             var popupScrollViewer = popup?.Child as ScrollViewer;

tests/Avalonia.Controls.UnitTests/CommandBarTests.cs

@@ -495,7 +495,7 @@ public class CommandBarDefaultsTests : ScopedTestBase
         command.ApplyStyling();
         command.ApplyTemplate();
 
-        var presenter = command.GetTemplateChildren()
+        var presenter = command.GetTemplateDescendants()
             .OfType<ContentPresenter>()
             .Single(x => x.Name == "PART_IconPresenter");
 

tests/Avalonia.Controls.UnitTests/ContentControlTests.cs

@@ -57,7 +57,7 @@ namespace Avalonia.Controls.UnitTests
             target.ApplyTemplate();
             target.Presenter!.ApplyTemplate();
 
-            foreach (Control child in target.GetTemplateChildren())
+            foreach (var child in target.GetTemplateDescendants().OfType<Control>())
                 Assert.Equal("foo", child.Tag);
         }
 

tests/Avalonia.Controls.UnitTests/NumericUpDownTests.cs

@@ -142,7 +142,7 @@ namespace Avalonia.Controls.UnitTests
         }
         private static TextBox GetTextBox(NumericUpDown control)
         {
-            return control.GetTemplateChildren()
+            return control.GetTemplateDescendants()
                           .OfType<ButtonSpinner>()
                           .Select(b => b.Content)
                           .OfType<TextBox>()
@@ -151,7 +151,7 @@ namespace Avalonia.Controls.UnitTests
 
         private static ButtonSpinner GetSpinner(NumericUpDown control)
         {
-            return control.GetTemplateChildren()
+            return control.GetTemplateDescendants()
                 .OfType<ButtonSpinner>()
                 .First();
         }

tests/Avalonia.Controls.UnitTests/Primitives/PopupTests.cs

@@ -329,7 +329,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
                 target.ApplyTemplate();
 
-                var popup = (Popup)target.GetTemplateChildren().First(x => x.Name == "popup");
+                var popup = (Popup)target.GetTemplateDescendants().First(x => x.Name == "popup");
                 popup.Open();
 
                 var popupRoot = (Control)popup.Host!;
@@ -420,7 +420,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
                 target.ApplyTemplate();
 
-                var popup = (Popup)target.GetTemplateChildren().First(x => x.Name == "popup");
+                var popup = (Popup)target.GetTemplateDescendants().First(x => x.Name == "popup");
                 popup.Open();
 
                 var popupRoot = (Control)popup.Host!;
@@ -515,7 +515,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
                 target.ApplyTemplate();
 
-                var popup = (Popup)target.GetTemplateChildren().First(x => x.Name == "popup");
+                var popup = (Popup)target.GetTemplateDescendants().First(x => x.Name == "popup");
                 popup.Open();
 
                 var popupRoot = (Control)popup.Host!;

tests/Avalonia.Controls.UnitTests/Primitives/ScrollBarTests.cs

@@ -20,7 +20,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             };
 
             target.ApplyTemplate();
-            var track = (Track)target.GetTemplateChildren().First(x => x.Name == "track");
+            var track = (Track)target.GetTemplateDescendants().First(x => x.Name == "track");
             target.Value = 50;
 
             Assert.Equal(50, track.Value);
@@ -35,7 +35,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             };
 
             target.ApplyTemplate();
-            var track = (Track)target.GetTemplateChildren().First(x => x.Name == "track");
+            var track = (Track)target.GetTemplateDescendants().First(x => x.Name == "track");
             track.Value = 50;
 
             Assert.Equal(50, target.Value);
@@ -51,7 +51,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             target.ApplyTemplate();
 
-            var track = (Track)target.GetTemplateChildren().First(x => x.Name == "track");
+            var track = (Track)target.GetTemplateDescendants().First(x => x.Name == "track");
             target.Value = 25;
             track.Value = 50;
 
@@ -68,7 +68,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             target.ApplyTemplate();
 
-            var track = (Track)target.GetTemplateChildren().First(x => x.Name == "track");
+            var track = (Track)target.GetTemplateDescendants().First(x => x.Name == "track");
 
             var raisedEvent = Assert.Raises<ScrollEventArgs>(
                 handler => target.Scroll += handler,
@@ -97,7 +97,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             target.ApplyTemplate();
 
-            var track = (Track)target.GetTemplateChildren().First(x => x.Name == "track");
+            var track = (Track)target.GetTemplateDescendants().First(x => x.Name == "track");
 
             var raisedEvent = Assert.Raises<ScrollEventArgs>(
                 handler => target.Scroll += handler,

tests/Avalonia.Controls.UnitTests/Primitives/TemplatedControlTests.cs

@@ -204,7 +204,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             target.ApplyTemplate();
 
-            foreach (Control child in target.GetTemplateChildren())
+            foreach (var child in target.GetTemplateDescendants().OfType<Control>())
                 Assert.Equal("foo", child.Tag);
         }
 
@@ -237,11 +237,11 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             target.ApplyTemplate();
 
-            var contentControl = target.GetTemplateChildren().OfType<ContentControl>().Single();
+            var contentControl = target.GetTemplateDescendants().OfType<ContentControl>().Single();
             contentControl.ApplyTemplate();
 
-            var border = contentControl.GetTemplateChildren().OfType<Border>().Single();
-            var presenter = contentControl.GetTemplateChildren().OfType<ContentPresenter>().Single();
+            var border = contentControl.GetTemplateDescendants().OfType<Border>().Single();
+            var presenter = contentControl.GetTemplateDescendants().OfType<ContentPresenter>().Single();
             var decorator = (Decorator)presenter.Content!;
             var textBlock = (TextBlock)decorator.Child!;
 

tests/Avalonia.Controls.UnitTests/ScrollViewerTests.cs

@@ -610,9 +610,9 @@ namespace Avalonia.Controls.UnitTests
         private Thumb GetVerticalThumb(ScrollViewer target)
         {
             var scrollbar = Assert.IsType<ScrollBar>(
-                target.GetTemplateChildren().FirstOrDefault(x => x.Name == "PART_VerticalScrollBar"));
+                target.GetTemplateDescendants().FirstOrDefault(x => x.Name == "PART_VerticalScrollBar"));
             var track = Assert.IsType<Track>(
-                scrollbar.GetTemplateChildren().FirstOrDefault(x => x.Name == "track"));
+                scrollbar.GetTemplateDescendants().FirstOrDefault(x => x.Name == "track"));
             return Assert.IsType<Thumb>(track.Thumb);
         }
 

tests/Avalonia.Controls.UnitTests/TabControlTests.cs

@@ -1701,7 +1701,7 @@ namespace Avalonia.Controls.UnitTests
             tabItem.ApplyTemplate();
             tabItem.Presenter!.UpdateChild();
 
-            var iconPresenter = tabItem.GetTemplateChildren().OfType<ContentPresenter>().First(x => x.Name == "PART_IconPresenter");
+            var iconPresenter = tabItem.GetTemplateDescendants().OfType<ContentPresenter>().First(x => x.Name == "PART_IconPresenter");
             Assert.NotNull(iconPresenter);
             Assert.Equal("home", iconPresenter!.Content);
             Assert.NotNull(iconPresenter.ContentTemplate);
@@ -1729,7 +1729,7 @@ namespace Avalonia.Controls.UnitTests
             tabItem.ApplyTemplate();
             tabItem.Presenter!.UpdateChild();
 
-            var iconPresenter = tabItem.GetTemplateChildren().OfType<ContentPresenter>().First(x => x.Name == "PART_IconPresenter");
+            var iconPresenter = tabItem.GetTemplateDescendants().OfType<ContentPresenter>().First(x => x.Name == "PART_IconPresenter");
             Assert.NotNull(iconPresenter);
             Assert.Same(icon, iconPresenter!.Content);
             Assert.Null(iconPresenter.ContentTemplate);
@@ -1748,7 +1748,7 @@ namespace Avalonia.Controls.UnitTests
             tabItem.ApplyTemplate();
             tabItem.Presenter!.UpdateChild();
 
-            var iconPresenter = tabItem.GetTemplateChildren().OfType<ContentPresenter>().First(x => x.Name == "PART_IconPresenter");
+            var iconPresenter = tabItem.GetTemplateDescendants().OfType<ContentPresenter>().First(x => x.Name == "PART_IconPresenter");
             Assert.Equal("first", iconPresenter!.Content);
 
             tabItem.Icon = "second";

tests/Avalonia.Controls.UnitTests/Templates/TemplateExtensionsTests.cs

@@ -38,7 +38,7 @@ namespace Avalonia.Controls.Templates.UnitTests
             border3.Child = border4;
             border4.Child = border5;
 
-            var result = target.GetTemplateChildren().Select(x => x.Name).ToArray();
+            var result = target.GetTemplateDescendants().Select(x => x.Name).ToArray();
 
             Assert.Equal(new[] { "border1", "inner", "border4" }, result);
         }

tests/Avalonia.Controls.UnitTests/TransitioningContentControlTests.cs

@@ -371,7 +371,7 @@ namespace Avalonia.Controls.UnitTests
         private static ContentPresenter GetContentPresenters2(TransitioningContentControl target)
         {
             return Assert.IsType<ContentPresenter>(target
-                .GetTemplateChildren()
+                .GetTemplateDescendants()
                 .First(x => x.Name == "PART_ContentPresenter2"));
         }
 

tests/Avalonia.LeakTests/ControlTests.cs

@@ -251,7 +251,7 @@ namespace Avalonia.LeakTests
                 Assert.Same(textBox, window.Presenter!.Child);
 
                 // Get the border from the TextBox template.
-                var border = textBox.GetTemplateChildren().FirstOrDefault(x => x.Name == "border");
+                var border = textBox.GetTemplateDescendants().FirstOrDefault(x => x.Name == "border");
 
                 // The TextBox should have subscriptions to its Classes collection from the
                 // default theme.

tests/Avalonia.Markup.Xaml.UnitTests/Data/BindingTests_TemplatedParent.cs

@@ -67,7 +67,7 @@ namespace Avalonia.Markup.Xaml.UnitTests.Data
                 window.ApplyTemplate();
                 button.ApplyTemplate();
 
-                Assert.Equal(button.Tag, button.GetTemplateChildren().OfType<Grid>().First().ColumnDefinitions[0].Width);
+                Assert.Equal(button.Tag, button.GetTemplateDescendants().OfType<Grid>().First().ColumnDefinitions[0].Width);
             }
         }
     }

tests/Avalonia.Markup.Xaml.UnitTests/MarkupExtensions/CompiledBindingExtensionTests.cs

@@ -1011,7 +1011,7 @@ namespace Avalonia.Markup.Xaml.UnitTests.MarkupExtensions
                 contentControl.DataContext = new TestDataContext(); // should be ignored
                 contentControl.Measure(new Size(10, 10));
                 
-                var result = contentControl.GetTemplateChildren().OfType<ContentPresenter>().First();
+                var result = contentControl.GetTemplateDescendants().OfType<ContentPresenter>().First();
                 Assert.Equal(false, result.Focusable);
             }
         }
@@ -1046,7 +1046,7 @@ namespace Avalonia.Markup.Xaml.UnitTests.MarkupExtensions
                 textBox.DataContext = new TestDataContext(); // should be ignored
                 textBox.Measure(new Size(10, 10));
                 
-                var result = textBox.GetTemplateChildren().OfType<ContentPresenter>().First();
+                var result = textBox.GetTemplateDescendants().OfType<ContentPresenter>().First();
                 Assert.Equal(textBox.InnerLeftContent, result.Content);
             }
         }
@@ -1080,7 +1080,7 @@ namespace Avalonia.Markup.Xaml.UnitTests.MarkupExtensions
                 window.ApplyTemplate();
                 button.ApplyTemplate();
 
-                Assert.Equal(button.Tag, button.GetTemplateChildren().OfType<Grid>().First().ColumnDefinitions[0].Width);
+                Assert.Equal(button.Tag, button.GetTemplateDescendants().OfType<Grid>().First().ColumnDefinitions[0].Width);
             }
         }
 
@@ -1109,7 +1109,7 @@ namespace Avalonia.Markup.Xaml.UnitTests.MarkupExtensions
                 var contentControl = AvaloniaRuntimeXamlLoader.Parse<ContentControl>(xaml);
                 contentControl.Measure(new Size(10, 10));
                 
-                var result = contentControl.GetTemplateChildren().OfType<ContentPresenter>().First();
+                var result = contentControl.GetTemplateDescendants().OfType<ContentPresenter>().First();
                 
                 Assert.Equal("Hello", result.Content);
             }