From 4f13d504967aa9be3ccd2123189dece3591d32ad Mon Sep 17 00:00:00 2001
From: Jurjen Biewenga <j.f.biewenga@gmail.com>
Date: Thu, 28 Sep 2017 15:53:05 +0200
Subject: [PATCH 1/3] Added initial changes to allow the user to change the
 selected item while the dropdown is closed but selected and allows the user
 to open the dropdown by pressing down

---
 src/Avalonia.Controls/DropDown.cs     | 24 ++++++++++++++++++++++++
 src/Avalonia.Controls/ItemsControl.cs | 11 +++++++++++
 2 files changed, 35 insertions(+)

diff --git a/src/Avalonia.Controls/DropDown.cs b/src/Avalonia.Controls/DropDown.cs
index 5349fb1ca7..63fd6726b4 100644
--- a/src/Avalonia.Controls/DropDown.cs
+++ b/src/Avalonia.Controls/DropDown.cs
@@ -114,6 +114,30 @@ namespace Avalonia.Controls
                     IsDropDownOpen = false;
                     e.Handled = true;
                 }
+
+                if (!IsDropDownOpen)
+                {
+                    if (e.Key == Key.Right)
+                    {
+                        if (++SelectedIndex >= ItemCount)
+                            SelectedIndex = 0;
+                        
+                        e.Handled = true;
+                    }
+                    else if (e.Key == Key.Left)
+                    {
+                        if (--SelectedIndex < 0)
+                            SelectedIndex = ItemCount - 1;
+                        e.Handled = true;
+                    }
+                    else if (e.Key == Key.Down)
+                    {
+                        IsDropDownOpen = true;
+                        if (SelectedIndex == -1)
+                            SelectedIndex = 0;
+                        e.Handled = true;
+                    }
+                }
             }
         }
 
diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index aa209e0462..4366de1cd6 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/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);

From 3081a07f1c64403a668049d8e0652255b26fc888 Mon Sep 17 00:00:00 2001
From: Jurjen Biewenga <j.f.biewenga@gmail.com>
Date: Mon, 16 Oct 2017 11:27:06 +0200
Subject: [PATCH 2/3] Made the requested changes

---
 src/Avalonia.Controls/DropDown.cs | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/src/Avalonia.Controls/DropDown.cs b/src/Avalonia.Controls/DropDown.cs
index c38f9ffd9e..cdb179cac9 100644
--- a/src/Avalonia.Controls/DropDown.cs
+++ b/src/Avalonia.Controls/DropDown.cs
@@ -104,7 +104,7 @@ 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;
@@ -117,24 +117,21 @@ namespace Avalonia.Controls
 
                 if (!IsDropDownOpen)
                 {
-                    if (e.Key == Key.Right)
+                    if (e.Key == Key.Down)
                     {
+                        if (SelectedIndex == -1)
+                            SelectedIndex = 0;
+                        
                         if (++SelectedIndex >= ItemCount)
                             SelectedIndex = 0;
                         
                         e.Handled = true;
                     }
-                    else if (e.Key == Key.Left)
+                    else if (e.Key == Key.Up)
                     {
                         if (--SelectedIndex < 0)
                             SelectedIndex = ItemCount - 1;
-                        e.Handled = true;
-                    }
-                    else if (e.Key == Key.Down)
-                    {
-                        IsDropDownOpen = true;
-                        if (SelectedIndex == -1)
-                            SelectedIndex = 0;
+                        
                         e.Handled = true;
                     }
                 }

From 2f4887318495bfbf1fffa772bf65e729a678eceb Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 19 Oct 2017 00:26:27 +0200
Subject: [PATCH 3/3] Select dropdown item on focus.

Arrow keys within the dropdown are handled by the keyboard navigation handler, so detect when this focuses a new item and select it.
---
 src/Avalonia.Controls/DropDown.cs | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/Avalonia.Controls/DropDown.cs b/src/Avalonia.Controls/DropDown.cs
index cdb179cac9..6b27c479ba 100644
--- a/src/Avalonia.Controls/DropDown.cs
+++ b/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)
         {