SelectingItemsControl.AutoScrollToSelectedItem

Added SelectingItemsControl.AutoScrollToSelectedItem. Closes #363.

src/Perspex.Controls/Mixins/SelectableMixin.cs

@@ -50,11 +50,14 @@ namespace Perspex.Controls.Mixins
 
                 if (sender != null)
                 {
+                    var itemsControl = sender.Parent as SelectingItemsControl;
+
                     if ((bool)x.NewValue)
                     {
                         ((IPseudoClasses)sender.Classes).Add(":selected");
 
-                        if (((IVisual)sender).IsAttachedToVisualTree)
+                        if (((IVisual)sender).IsAttachedToVisualTree && 
+                            itemsControl?.AutoScrollToSelectedItem == true)
                         {
                             sender.BringIntoView();
                         }

src/Perspex.Controls/Primitives/SelectingItemsControl.cs

@@ -38,6 +38,14 @@ namespace Perspex.Controls.Primitives
     /// </remarks>
     public class SelectingItemsControl : ItemsControl
     {
+        /// <summary>
+        /// Defines the <see cref="AutoScrollToSelectedItem"/> property.
+        /// </summary>
+        public static readonly StyledProperty<bool> AutoScrollToSelectedItemProperty =
+            PerspexProperty.Register<SelectingItemsControl, bool>(
+                nameof(AutoScrollToSelectedItem),
+                defaultValue: true);
+
         /// <summary>
         /// Defines the <see cref="SelectedIndex"/> property.
         /// </summary>
@@ -123,6 +131,15 @@ namespace Perspex.Controls.Primitives
             remove { RemoveHandler(SelectionChangedEvent, value); }
         }
 
+        /// <summary>
+        /// Gets or sets a value indicating whether to automatically scroll to newly selected items.
+        /// </summary>
+        public bool AutoScrollToSelectedItem
+        {
+            get { return GetValue(AutoScrollToSelectedItemProperty); }
+            set { SetValue(AutoScrollToSelectedItemProperty, value); }
+        }
+
         /// <summary>
         /// Gets or sets the index of the selected item.
         /// </summary>

src/Perspex.Controls/TreeView.cs

@@ -22,9 +22,7 @@ namespace Perspex.Controls
         /// Defines the <see cref="AutoScrollToSelectedItem"/> property.
         /// </summary>
         public static readonly StyledProperty<bool> AutoScrollToSelectedItemProperty =
-            PerspexProperty.Register<TreeView, bool>(
-                nameof(AutoScrollToSelectedItem),
-                defaultValue: true);
+            SelectingItemsControl.AutoScrollToSelectedItemProperty.AddOwner<TreeView>();
 
         /// <summary>
         /// Defines the <see cref="SelectedItem"/> property.