From 8a0ccea2731e2df48d105f9e5fea25e6f1361fb9 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Sat, 22 Feb 2020 10:02:19 +0100
Subject: [PATCH] Add MenuItem.InputGestureText.

---
 src/Avalonia.Controls/MenuItem.cs         | 51 +++++++++++++++++++++++
 src/Avalonia.Themes.Default/MenuItem.xaml | 26 ++++++++----
 2 files changed, 70 insertions(+), 7 deletions(-)

diff --git a/src/Avalonia.Controls/MenuItem.cs b/src/Avalonia.Controls/MenuItem.cs
index e0baa5e679..ae36b5d830 100644
--- a/src/Avalonia.Controls/MenuItem.cs
+++ b/src/Avalonia.Controls/MenuItem.cs
@@ -13,6 +13,7 @@ using Avalonia.Data;
 using Avalonia.Input;
 using Avalonia.Interactivity;
 using Avalonia.LogicalTree;
+using Avalonia.VisualTree;
 
 namespace Avalonia.Controls
 {
@@ -48,6 +49,12 @@ namespace Avalonia.Controls
         public static readonly StyledProperty<object> IconProperty =
             AvaloniaProperty.Register<MenuItem, object>(nameof(Icon));
 
+        /// <summary>
+        /// Defines the <see cref="InputGestureText"/> property.
+        /// </summary>
+        public static readonly StyledProperty<string> InputGestureTextProperty =
+            AvaloniaProperty.Register<MenuItem, string>(nameof(InputGestureText));
+
         /// <summary>
         /// Defines the <see cref="IsSelected"/> property.
         /// </summary>
@@ -93,6 +100,7 @@ namespace Avalonia.Controls
         private ICommand _command;
         private bool _commandCanExecute = true;
         private Popup _popup;
+        private IDisposable _gridHack;
 
         /// <summary>
         /// Initializes static members of the <see cref="MenuItem"/> class.
@@ -194,6 +202,19 @@ namespace Avalonia.Controls
             set { SetValue(IconProperty, value); }
         }
 
+        /// <summary>
+        /// Gets or sets the input gesture that will be displayed in the menu item.
+        /// </summary>
+        /// <remarks>
+        /// Setting this property does not cause the input gesture to be handled by the menu item,
+        /// it simply displays the gesture text in the menu.
+        /// </remarks>
+        public object InputGestureText
+        {
+            get { return GetValue(InputGestureTextProperty); }
+            set { SetValue(InputGestureTextProperty, value); }
+        }
+
         /// <summary>
         /// Gets or sets a value indicating whether the <see cref="MenuItem"/> is currently selected.
         /// </summary>
@@ -306,6 +327,36 @@ namespace Avalonia.Controls
             }
         }
 
+        protected override void OnAttachedToVisualTree(VisualTreeAttachmentEventArgs e)
+        {
+            base.OnAttachedToVisualTree(e);
+
+            if (this.GetVisualParent() is IControl parent)
+            {
+                // HACK: This nasty but it's all WPF's fault. Grid uses an inherited attached
+                // property to store SharedSizeGroup state, except property inheritance is done
+                // down the logical tree. In this case, the control which is setting
+                // Grid.IsSharedSizeScope="True" is not in the logical tree. Instead of fixing
+                // the way Grid stores shared size state, the developers of WPF just created a
+                // binding of the internal state of the visual parent to the menu item. We don't
+                // have much choice but to do the same for now unless we want to refactor Grid,
+                // which I honestly am not brave enough to do right now. Here's the same hack in
+                // the WPF codebase:
+                //
+                // https://github.com/dotnet/wpf/blob/89537909bdf36bc918e88b37751add46a8980bb0/src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Controls/MenuItem.cs#L2126-L2141
+                _gridHack = Bind(
+                    DefinitionBase.PrivateSharedSizeScopeProperty,
+                    parent.GetBindingObservable(DefinitionBase.PrivateSharedSizeScopeProperty));
+            }
+        }
+
+        protected override void OnDetachedFromVisualTree(VisualTreeAttachmentEventArgs e)
+        {
+            base.OnDetachedFromVisualTree(e);
+            _gridHack.Dispose();
+            _gridHack = null;
+        }
+
         /// <summary>
         /// Called when the <see cref="MenuItem"/> is clicked.
         /// </summary>
diff --git a/src/Avalonia.Themes.Default/MenuItem.xaml b/src/Avalonia.Themes.Default/MenuItem.xaml
index 93989d3782..431adacb47 100644
--- a/src/Avalonia.Themes.Default/MenuItem.xaml
+++ b/src/Avalonia.Themes.Default/MenuItem.xaml
@@ -11,7 +11,14 @@
                 Background="{TemplateBinding Background}"
                 BorderBrush="{TemplateBinding BorderBrush}"
                 BorderThickness="{TemplateBinding BorderThickness}">
-          <Grid ColumnDefinitions="20,5,*,20">
+          <Grid>
+            <Grid.ColumnDefinitions>
+              <ColumnDefinition Width="20"/>
+              <ColumnDefinition Width="5"/>
+              <ColumnDefinition Width="*"/>
+              <ColumnDefinition Width="Auto" SharedSizeGroup="MenuItemIGT"/>
+              <ColumnDefinition Width="20"/>
+            </Grid.ColumnDefinitions>
             <ContentPresenter Name="icon"
                               Content="{TemplateBinding Icon}"
                               Width="16"
@@ -36,12 +43,15 @@
                 </DataTemplate>
               </ContentPresenter.DataTemplates>
             </ContentPresenter>
+            <TextBlock Grid.Column="3"
+                       Text="{TemplateBinding InputGestureText}"
+                       VerticalAlignment="Center"/>
             <Path Name="rightArrow"
                   Data="M0,0L4,3.5 0,7z"
                   Fill="{DynamicResource ThemeForegroundBrush}"
                   Margin="10,0,0,0"
                   VerticalAlignment="Center"
-                  Grid.Column="3"/>
+                  Grid.Column="4"/>
             <Popup Name="PART_Popup"
                    PlacementMode="Right"
                    StaysOpen="True"
@@ -55,7 +65,8 @@
                                     Items="{TemplateBinding Items}"
                                     ItemsPanel="{TemplateBinding ItemsPanel}"
                                     ItemTemplate="{TemplateBinding ItemTemplate}"
-                                    Margin="4 2"/>                                      
+                                    Margin="4 2"
+                                    Grid.IsSharedSizeScope="True"/>
                 </ScrollViewer>
               </Border>
             </Popup>
@@ -102,10 +113,11 @@
                       BorderThickness="{TemplateBinding BorderThickness}">
                 <ScrollViewer>
                   <ItemsPresenter Name="PART_ItemsPresenter"
-                                    Items="{TemplateBinding Items}"
-                                    ItemsPanel="{TemplateBinding ItemsPanel}"
-                                    ItemTemplate="{TemplateBinding ItemTemplate}"
-                                    Margin="2"/>
+                                  Items="{TemplateBinding Items}"
+                                  ItemsPanel="{TemplateBinding ItemsPanel}"
+                                  ItemTemplate="{TemplateBinding ItemTemplate}"
+                                  Margin="2"
+                                  Grid.IsSharedSizeScope="True"/>
                 </ScrollViewer>
               </Border>
             </Popup>