Merge pull request #2782 from AvaloniaUI/fixes/2003-treeview-autoscroll

Fix scrolling to selected item in TreeView.

src/Avalonia.Controls/ControlExtensions.cs

@@ -34,14 +34,17 @@ namespace Avalonia.Controls
         {
             Contract.Requires<ArgumentNullException>(control != null);
 
-            var ev = new RequestBringIntoViewEventArgs
+            if (control.IsEffectivelyVisible)
             {
-                RoutedEvent = Control.RequestBringIntoViewEvent,
-                TargetObject = control,
-                TargetRect = rect,
-            };
+                var ev = new RequestBringIntoViewEventArgs
+                {
+                    RoutedEvent = Control.RequestBringIntoViewEvent,
+                    TargetObject = control,
+                    TargetRect = rect,
+                };
 
-            control.RaiseEvent(ev);
+                control.RaiseEvent(ev);
+            }
         }
 
         /// <summary>

src/Avalonia.Controls/Presenters/ScrollContentPresenter.cs

@@ -141,7 +141,7 @@ namespace Avalonia.Controls.Presenters
         /// <returns>True if the scroll offset was changed; otherwise false.</returns>
         public bool BringDescendantIntoView(IVisual target, Rect targetRect)
         {
-            if (Child == null)
+            if (Child?.IsEffectivelyVisible != true)
             {
                 return false;
             }

src/Avalonia.Controls/TreeViewItem.cs

@@ -42,6 +42,7 @@ namespace Avalonia.Controls
             new FuncTemplate<IPanel>(() => new StackPanel());
 
         private TreeView _treeView;
+        private IControl _header;
         private bool _isExpanded;
         private int _level;
 
@@ -53,6 +54,7 @@ namespace Avalonia.Controls
             SelectableMixin.Attach<TreeViewItem>(IsSelectedProperty);
             FocusableProperty.OverrideDefaultValue<TreeViewItem>(true);
             ItemsPanelProperty.OverrideDefaultValue<TreeViewItem>(DefaultPanel);
+            RequestBringIntoViewEvent.AddClassHandler<TreeViewItem>(x => x.OnRequestBringIntoView);
         }
 
         /// <summary>
@@ -120,6 +122,21 @@ namespace Avalonia.Controls
             ItemContainerGenerator.Clear();
         }
 
+        protected virtual void OnRequestBringIntoView(RequestBringIntoViewEventArgs e)
+        {
+            if (e.TargetObject == this && _header != null)
+            {
+                var m = _header.TransformToVisual(this);
+
+                if (m.HasValue)
+                {
+                    var bounds = new Rect(_header.Bounds.Size);
+                    var rect = bounds.TransformToAABB(m.Value);
+                    e.TargetRect = rect;
+                }
+            }
+        }
+
         /// <inheritdoc/>
         protected override void OnKeyDown(KeyEventArgs e)
         {
@@ -146,6 +163,12 @@ namespace Avalonia.Controls
             // Don't call base.OnKeyDown - let events bubble up to containing TreeView.
         }
 
+        protected override void OnTemplateApplied(TemplateAppliedEventArgs e)
+        {
+            base.OnTemplateApplied(e);
+            _header = e.NameScope.Find<IControl>("PART_Header");
+        }
+
         private static int CalculateDistanceFromLogicalParent<T>(ILogical logical, int @default = -1) where T : class
         {
             var result = 0;

src/Avalonia.Themes.Default/TreeViewItem.xaml

@@ -16,7 +16,9 @@
                             BorderBrush="{TemplateBinding BorderBrush}"
                             BorderThickness="{TemplateBinding BorderThickness}"
                             TemplatedControl.IsTemplateFocusTarget="True">
-                        <Grid ColumnDefinitions="16, *"
+                        <Grid Name="PART_Header"
+                              ColumnDefinitions="16, Auto"
+                              HorizontalAlignment="Left"
                               Margin="{TemplateBinding Level, Mode=OneWay, Converter={StaticResource LeftMarginConverter}}" >
                             <ToggleButton Name="expander"
                                           Focusable="False"