Added ScrollViewer to TreeViewStyle.

Perspex.Controls/Presenters/ContentPresenter.cs

@@ -30,6 +30,16 @@ namespace Perspex.Controls.Presenters
             set { this.SetValue(ContentProperty, value); }
         }
 
+        protected override Size MeasureCore(Size availableSize)
+        {
+            if (!this.createdChild)
+            {
+                this.CreateChild();
+            }
+
+            return base.MeasureCore(availableSize);
+        }
+
         protected override Size MeasureOverride(Size availableSize)
         {
             if (!this.createdChild)
@@ -85,7 +95,14 @@ namespace Perspex.Controls.Presenters
                     }
                 }
 
-                result.TemplatedParent = null;
+                var foo = this.TemplatedParent as TemplatedControl;
+
+                if (foo != null)
+                {
+                    foo = foo.TemplatedParent as TemplatedControl;
+                }
+
+                result.TemplatedParent = foo;
                 this.AddVisualChild(result);
             }
 

Perspex.Controls/Presenters/ItemsPresenter.cs

@@ -63,8 +63,8 @@ namespace Perspex.Controls.Presenters
             this.ClearVisualChildren();
             this.panel = this.ItemsPanel.Build();
             this.AddVisualChild(this.panel);
-            this.ItemsChanged(Tuple.Create(default(IEnumerable), this.Items));
             this.createdPanel = true;
+            this.ItemsChanged(Tuple.Create(default(IEnumerable), this.Items));
         }
 
         private IItemContainerGenerator GetGenerator()
@@ -81,31 +81,34 @@ namespace Perspex.Controls.Presenters
 
         private void ItemsChanged(Tuple<IEnumerable, IEnumerable> value)
         {
-            var generator = this.GetGenerator();
-
-            if (value.Item1 != null)
+            if (this.createdPanel)
             {
-                this.panel.Children.RemoveAll(generator.Remove(value.Item1));
-
-                INotifyCollectionChanged incc = value.Item1 as INotifyCollectionChanged;
+                var generator = this.GetGenerator();
 
-                if (incc != null)
+                if (value.Item1 != null)
                 {
-                    incc.CollectionChanged -= this.ItemsCollectionChanged;
+                    this.panel.Children.RemoveAll(generator.Remove(value.Item1));
+
+                    INotifyCollectionChanged incc = value.Item1 as INotifyCollectionChanged;
+
+                    if (incc != null)
+                    {
+                        incc.CollectionChanged -= this.ItemsCollectionChanged;
+                    }
                 }
-            }
 
-            if (this.panel != null)
-            {
-                if (value.Item2 != null)
+                if (this.panel != null)
                 {
-                    this.panel.Children.AddRange(generator.Generate(this.Items));
+                    if (value.Item2 != null)
+                    {
+                        this.panel.Children.AddRange(generator.Generate(this.Items));
 
-                    INotifyCollectionChanged incc = value.Item2 as INotifyCollectionChanged;
+                        INotifyCollectionChanged incc = value.Item2 as INotifyCollectionChanged;
 
-                    if (incc != null)
-                    {
-                        incc.CollectionChanged += this.ItemsCollectionChanged;
+                        if (incc != null)
+                        {
+                            incc.CollectionChanged += this.ItemsCollectionChanged;
+                        }
                     }
                 }
             }
@@ -113,7 +116,7 @@ namespace Perspex.Controls.Presenters
 
         private void ItemsCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
         {
-            if (this.panel != null)
+            if (this.createdPanel)
             {
                 var generator = this.GetGenerator();
 

Perspex.Themes.Default/TreeViewStyle.cs

@@ -38,10 +38,13 @@ namespace Perspex.Themes.Default
                 [~Border.BackgroundProperty] = control[~TreeView.BackgroundProperty],
                 [~Border.BorderBrushProperty] = control[~TreeView.BorderBrushProperty],
                 [~Border.BorderThicknessProperty] = control[~TreeView.BorderThicknessProperty],
-                Content = new ItemsPresenter
+                Content = new ScrollViewer
                 {
-                    [~ItemsPresenter.ItemsProperty] = control[~TreeView.ItemsProperty],
-                    [~ItemsPresenter.ItemsPanelProperty] = control[~TreeView.ItemsPanelProperty],
+                    Content = new ItemsPresenter
+                    {
+                        [~ItemsPresenter.ItemsProperty] = control[~TreeView.ItemsProperty],
+                        [~ItemsPresenter.ItemsPanelProperty] = control[~TreeView.ItemsPanelProperty],
+                    }
                 }
             };
         }