show adorner while hovering any part of the control's TreeViewItem in DevTools (#14231)

src/Avalonia.Diagnostics/Diagnostics/Views/TreePageView.xaml

@@ -7,13 +7,12 @@
     <TreeView Name="tree"
               BorderThickness="0"
               ItemsSource="{Binding Nodes}"
-              SelectedItem="{Binding SelectedNode, Mode=TwoWay}">
+              SelectedItem="{Binding SelectedNode, Mode=TwoWay}"
+              PointerMoved="UpdateAdorner">
       <TreeView.DataTemplates>
         <TreeDataTemplate DataType="vm:TreeNode"
                           ItemsSource="{Binding Children}">
-          <StackPanel Orientation="Horizontal" Spacing="8"
+          <StackPanel Orientation="Horizontal" Spacing="8">
-                      PointerEntered="AddAdorner"
-                      PointerExited="RemoveAdorner">
             <TextBlock Text="{Binding Type}" FontWeight="{Binding FontWeight}"/>
             <TextBlock Text="{Binding Classes}"/>
             <TextBlock Foreground="Gray" Text="{Binding ElementName}"/>

src/Avalonia.Diagnostics/Diagnostics/Views/TreePageView.xaml.cs

@@ -1,14 +1,11 @@
-using System;
-using System.Diagnostics;
 using System.Linq;
 using Avalonia.Controls;
-using Avalonia.Controls.Generators;
 using Avalonia.Controls.Primitives;
 using Avalonia.Diagnostics.ViewModels;
 using Avalonia.Input;
+using Avalonia.LogicalTree;
 using Avalonia.Markup.Xaml;
 using Avalonia.Media;
-using Avalonia.VisualTree;
 
 namespace Avalonia.Diagnostics.Views
 {
@@ -16,6 +13,7 @@ namespace Avalonia.Diagnostics.Views
     {
         private readonly Panel _adorner;
         private AdornerLayer? _currentLayer;
+        private TreeViewItem? _hovered;
         private TreeView _tree;
 
         public TreePageView()
@@ -39,6 +37,11 @@ namespace Avalonia.Diagnostics.Views
             AdornerLayer.SetIsClipEnabled(_adorner, false);
         }
 
+        private static Thickness InvertThickness(Thickness input)
+        {
+            return new Thickness(-input.Left, -input.Top, -input.Right, -input.Bottom);
+        }
+
         protected void AddAdorner(object? sender, PointerEventArgs e)
         {
             var node = (TreeNode?)((Control)sender!).DataContext;
@@ -80,11 +83,6 @@ namespace Avalonia.Diagnostics.Views
             }
         }
 
-        private static Thickness InvertThickness(Thickness input)
-        {
-            return new Thickness(-input.Left, -input.Top, -input.Right, -input.Bottom);
-        }
-
         protected void RemoveAdorner(object? sender, PointerEventArgs e)
         {
             foreach (var border in _adorner.Children.OfType<Border>())
@@ -98,6 +96,31 @@ namespace Avalonia.Diagnostics.Views
             _currentLayer = null;
         }
 
+        protected void UpdateAdorner(object? sender, PointerEventArgs e)
+        {
+            if (e.Source is not StyledElement source)
+            {
+                return;
+            }
+
+            var item = source.FindLogicalAncestorOfType<TreeViewItem>();
+            if (item == _hovered)
+            {
+                return;
+            }
+
+            RemoveAdorner(sender, e);
+
+            if (item is null || item.TreeViewOwner != _tree)
+            {
+                _hovered = null;
+                return;
+            }
+
+            _hovered = item;
+            AddAdorner(item, e);
+        }
+
         protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
         {
             base.OnPropertyChanged(change);