SharpTreeView: improve left/right keyboard navigation

SharpTreeView/SharpTreeView.cs

@@ -6,12 +6,14 @@ using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
 using System.Text;
-using System.Windows.Controls;
 using System.Windows;
-using System.Windows.Media;
+using System.Windows.Controls;
+using System.Windows.Controls.Primitives;
 using System.Windows.Data;
 using System.Windows.Documents;
 using System.Windows.Input;
+using System.Windows.Media;
+using System.Windows.Threading;
 
 namespace ICSharpCode.TreeView
 {
@@ -158,6 +160,64 @@ namespace ICSharpCode.TreeView
 			}
 		}
 		
+		protected override void OnKeyDown(KeyEventArgs e)
+		{
+			switch (e.Key) {
+				case Key.Left:
+				case Key.Right:
+					SharpTreeViewItem container = e.OriginalSource as SharpTreeViewItem;
+					if (container != null && ItemsControl.ItemsControlFromItemContainer(container) == this) {
+						bool newExpanded = (e.Key == Key.Right);
+						if (container.Node.IsExpanded != newExpanded) {
+							container.Node.IsExpanded = newExpanded;
+						} else {
+							// already in collapsed/expanded - jump to parent/first child:
+							if (e.Key == Key.Right) {
+								container.MoveFocus(new TraversalRequest(FocusNavigationDirection.Down));
+							} else if (container.Node.Parent != null) {
+								this.FocusNode(container.Node.Parent);
+							}
+						}
+						e.Handled = true;
+					}
+					break;
+				default:
+					base.OnKeyDown(e);
+					break;
+			}
+		}
+		
+		public void FocusNode(SharpTreeNode node)
+		{
+			if (node == null)
+				throw new ArgumentNullException("node");
+			ScrollIntoView(node);
+			// WPF's ScrollIntoView() uses the same if/dispatcher construct, so we call OnFocusItem() after the item was brought into view.
+			if (this.ItemContainerGenerator.Status == GeneratorStatus.ContainersGenerated) {
+				OnFocusItem(node);
+			} else {
+				this.Dispatcher.BeginInvoke(DispatcherPriority.Loaded, new DispatcherOperationCallback(this.OnFocusItem), node);
+			}
+		}
+		
+		public void ScrollIntoView(SharpTreeNode node)
+		{
+			if (node == null)
+				throw new ArgumentNullException("node");
+			foreach (SharpTreeNode ancestor in node.Ancestors())
+				ancestor.IsExpanded = true;
+			base.ScrollIntoView(node);
+		}
+		
+		object OnFocusItem(object item)
+		{
+			FrameworkElement element = this.ItemContainerGenerator.ContainerFromItem(item) as FrameworkElement;
+			if (element != null) {
+				element.Focus();
+			}
+			return null;
+		}
+
 		#region Track selection
 		
 		protected override void OnSelectionChanged(SelectionChangedEventArgs e)

SharpTreeView/SharpTreeViewItem.cs

@@ -42,12 +42,6 @@ namespace ICSharpCode.TreeView
 				case Key.Escape:
 					Node.IsEditing = false;
 					break;
-				case Key.Left:
-					Node.IsExpanded = false;
-					break;
-				case Key.Right:
-					Node.IsExpanded = true;
-					break;
 			}
 		}