Merge pull request #1166 from JurjenBiewenga/DropdownKeyboardTweaks

Added initial changes to dropdown

src/Avalonia.Controls/DropDown.cs

@@ -96,6 +96,16 @@ namespace Avalonia.Controls
             this.UpdateSelectionBoxItem(this.SelectedItem);
         }
 
+        protected override void OnGotFocus(GotFocusEventArgs e)
+        {
+            base.OnGotFocus(e);
+
+            if (!e.Handled && e.NavigationMethod == NavigationMethod.Directional)
+            {
+                e.Handled = UpdateSelectionFromEventSource(e.Source);
+            }
+        }
+
         /// <inheritdoc/>
         protected override void OnKeyDown(KeyEventArgs e)
         {
@@ -104,7 +114,7 @@ namespace Avalonia.Controls
             if (!e.Handled)
             {
                 if (e.Key == Key.F4 ||
-                    (e.Key == Key.Down && ((e.Modifiers & InputModifiers.Alt) != 0)))
+                    ((e.Key == Key.Down || e.Key == Key.Up) && ((e.Modifiers & InputModifiers.Alt) != 0)))
                 {
                     IsDropDownOpen = !IsDropDownOpen;
                     e.Handled = true;
@@ -114,6 +124,27 @@ namespace Avalonia.Controls
                     IsDropDownOpen = false;
                     e.Handled = true;
                 }
+
+                if (!IsDropDownOpen)
+                {
+                    if (e.Key == Key.Down)
+                    {
+                        if (SelectedIndex == -1)
+                            SelectedIndex = 0;
+                        
+                        if (++SelectedIndex >= ItemCount)
+                            SelectedIndex = 0;
+                        
+                        e.Handled = true;
+                    }
+                    else if (e.Key == Key.Up)
+                    {
+                        if (--SelectedIndex < 0)
+                            SelectedIndex = ItemCount - 1;
+                        
+                        e.Handled = true;
+                    }
+                }
             }
         }
 

src/Avalonia.Controls/ItemsControl.cs

@@ -11,6 +11,7 @@ using Avalonia.Controls.Presenters;
 using Avalonia.Controls.Primitives;
 using Avalonia.Controls.Templates;
 using Avalonia.Controls.Utils;
+using Avalonia.Input;
 using Avalonia.LogicalTree;
 using Avalonia.Metadata;
 
@@ -106,6 +107,12 @@ namespace Avalonia.Controls
             set { SetAndRaise(ItemsProperty, ref _items, value); }
         }
 
+        public int ItemCount
+        {
+            get;
+            private set;
+        }
+
         /// <summary>
         /// Gets or sets the panel used to display the items.
         /// </summary>
@@ -352,6 +359,10 @@ namespace Avalonia.Controls
                     RemoveControlItemsFromLogicalChildren(e.OldItems);
                     break;
             }
+            
+            int? count = (Items as IList)?.Count;
+            if (count != null)
+                ItemCount = (int)count;
 
             var collection = sender as ICollection;
             PseudoClasses.Set(":empty", collection == null || collection.Count == 0);