Display gestures in NativeMenuBar.

To do this we needed to change the `KeyGesture.ToString()` method to produce input gesture text suitable for menus. Also demonstrated in `MainWindow` how to produce different gestures/headers depending on platform.

samples/ControlCatalog/MainWindow.xaml

@@ -14,7 +14,7 @@
       <NativeMenuItem Header="File">
         <NativeMenuItem.Menu>
           <NativeMenu>
-            <NativeMenuItem Header="Open" Clicked="OnOpenClicked"/>
+            <NativeMenuItem Header="Open" Clicked="OnOpenClicked" Gesture="Ctrl+O"/>
             <NativeMenuItemSeperator/>
             <NativeMenuItem Header="Recent">
               <NativeMenuItem.Menu>
@@ -22,7 +22,9 @@
               </NativeMenuItem.Menu>
             </NativeMenuItem>
             <NativeMenuItemSeperator/>
-            <NativeMenuItem Header="Quit Avalonia" Clicked="OnCloseClicked" Gesture="CMD+Q"/>
+            <NativeMenuItem Header="{x:Static local:MainWindow.MenuQuitHeader}"
+                            Gesture="{x:Static local:MainWindow.MenuQuitGesture}"
+                            Clicked="OnCloseClicked" />
           </NativeMenu>
         </NativeMenuItem.Menu>
       </NativeMenuItem>

samples/ControlCatalog/MainWindow.xaml.cs

@@ -1,13 +1,11 @@
+using System;
+using System.Runtime.InteropServices;
 using Avalonia;
 using Avalonia.Controls;
 using Avalonia.Controls.Notifications;
-using Avalonia.Controls.Primitives;
+using Avalonia.Input;
 using Avalonia.Markup.Xaml;
-using Avalonia.Threading;
 using ControlCatalog.ViewModels;
-using System;
-using System.Collections.Generic;
-using System.Threading.Tasks;
 
 namespace ControlCatalog
 {
@@ -35,6 +33,12 @@ namespace ControlCatalog
             mainMenu.AttachedToVisualTree += MenuAttached;
         }
 
+        public static string MenuQuitHeader => RuntimeInformation.IsOSPlatform(OSPlatform.OSX) ? "Quit Avalonia" : "E_xit";
+
+        public static KeyGesture MenuQuitGesture => RuntimeInformation.IsOSPlatform(OSPlatform.OSX) ?
+            new KeyGesture(Key.Q, KeyModifiers.Meta) :
+            new KeyGesture(Key.F4, KeyModifiers.Alt);
+
         public void MenuAttached(object sender, VisualTreeAttachmentEventArgs e)
         {
             if (NativeMenu.GetIsNativeMenuExported(this) && sender is Menu mainMenu)

src/Avalonia.Input/KeyGesture.cs

@@ -1,9 +1,10 @@
-// Copyright (c) The Avalonia Project. All rights reserved.
+// Copyright (c) The Avalonia Project. All rights reserved.
 // Licensed under the MIT license. See licence.md file in the project root for full license information.
 
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Text;
 
 namespace Avalonia.Input
 {
@@ -108,19 +109,43 @@ namespace Avalonia.Input
 
         public override string ToString()
         {
-            var parts = new List<string>();
+            var s = new StringBuilder();
 
-            foreach (var flag in Enum.GetValues(typeof(KeyModifiers)).Cast<KeyModifiers>())
+            static void Plus(StringBuilder s)
             {
-                if (KeyModifiers.HasFlag(flag) && flag != KeyModifiers.None)
+                if (s.Length > 0)
                 {
-                    parts.Add(flag.ToString());
+                    s.Append("+");
                 }
             }
 
-            parts.Add(Key.ToString());
+            if (KeyModifiers.HasFlagCustom(KeyModifiers.Control))
+            {
+                s.Append("Ctrl");
+            }
+
+            if (KeyModifiers.HasFlagCustom(KeyModifiers.Shift))
+            {
+                Plus(s);
+                s.Append("Shift");
+            }
+            
+            if (KeyModifiers.HasFlagCustom(KeyModifiers.Alt))
+            {
+                Plus(s);
+                s.Append("Alt");
+            }
+            
+            if (KeyModifiers.HasFlagCustom(KeyModifiers.Meta))
+            {
+                Plus(s);
+                s.Append("⌘");
+            }
+
+            Plus(s);
+            s.Append(Key);
 
-            return string.Join(" + ", parts);
+            return s.ToString();
         }
 
         public bool Matches(KeyEventArgs keyEvent) => ResolveNumPadOperationKey(keyEvent.Key) == Key && keyEvent.KeyModifiers == KeyModifiers;
@@ -141,7 +166,8 @@ namespace Avalonia.Input
                 return KeyModifiers.Control;
             }
 
-            if (modifier.Equals("cmd".AsSpan(), StringComparison.OrdinalIgnoreCase))
+            if (modifier.Equals("cmd".AsSpan(), StringComparison.OrdinalIgnoreCase) ||
+                modifier.Equals("⌘".AsSpan(), StringComparison.OrdinalIgnoreCase))
             {
                 return KeyModifiers.Meta;
             }

src/Avalonia.Themes.Default/NativeMenuBar.xaml

@@ -13,6 +13,7 @@
         <Menu.Styles>
           <Style Selector="MenuItem">
             <Setter Property="Header" Value="{Binding Header}"/>
+            <Setter Property="InputGestureText" Value="{Binding Gesture}"/>
             <Setter Property="Items" Value="{Binding Menu.Items}"/>
             <Setter Property="Command" Value="{Binding Command}"/>
             <Setter Property="CommandParameter" Value="{Binding CommandParameter}"/>

tests/Avalonia.Input.UnitTests/KeyGestureTests.cs

@@ -1,19 +1,31 @@
-using System.Collections.Generic;
+using System.Collections.Generic;
 using Xunit;
 
 namespace Avalonia.Input.UnitTests
 {
     public class KeyGestureTests
     {
-        public static readonly IEnumerable<object[]> SampleData = new object[][]
+        public static readonly IEnumerable<object[]> ParseData = new object[][]
         {
-            new object[]{"Ctrl+A", new KeyGesture(Key.A, InputModifiers.Control)},
-            new object[]{"  \tShift\t+Alt +B", new KeyGesture(Key.B, InputModifiers.Shift | InputModifiers.Alt) },
-            new object[]{"Control++", new KeyGesture(Key.OemPlus, InputModifiers.Control) }
+            new object[]{"Ctrl+A", new KeyGesture(Key.A, KeyModifiers.Control)},
+            new object[]{"  \tShift\t+Alt +B", new KeyGesture(Key.B, KeyModifiers.Shift | KeyModifiers.Alt) },
+            new object[]{"Control++", new KeyGesture(Key.OemPlus, KeyModifiers.Control) },
+            new object[]{ "Shift+⌘+A", new KeyGesture(Key.A, KeyModifiers.Meta | KeyModifiers.Shift) },
+            new object[]{ "Shift+Cmd+A", new KeyGesture(Key.A, KeyModifiers.Meta | KeyModifiers.Shift) },
+        };
+
+        public static readonly IEnumerable<object[]> ToStringData = new object[][]
+        {
+            new object[]{new KeyGesture(Key.A), "A"},
+            new object[]{new KeyGesture(Key.A, KeyModifiers.Control), "Ctrl+A"},
+            new object[]{new KeyGesture(Key.A, KeyModifiers.Control | KeyModifiers.Shift), "Ctrl+Shift+A"},
+            new object[]{new KeyGesture(Key.A, KeyModifiers.Alt | KeyModifiers.Shift), "Shift+Alt+A"},
+            new object[]{new KeyGesture(Key.A, KeyModifiers.Control | KeyModifiers.Alt | KeyModifiers.Shift), "Ctrl+Shift+Alt+A"},
+            new object[]{new KeyGesture(Key.A, KeyModifiers.Meta | KeyModifiers.Shift), "Shift+⌘+A"},
         };
 
         [Theory]
-        [MemberData(nameof(SampleData))]
+        [MemberData(nameof(ParseData))]
         public void Key_Gesture_Is_Able_To_Parse_Sample_Data(string text, KeyGesture gesture)
         {
             Assert.Equal(gesture, KeyGesture.Parse(text));
@@ -32,5 +44,12 @@ namespace Avalonia.Input.UnitTests
                 Key = pressedKey
             }));
         }
+
+        [Theory]
+        [MemberData(nameof(ToStringData))]
+        public void ToString_Produces_Correct_Results(KeyGesture gesture, string expected)
+        {
+            Assert.Equal(expected, gesture.ToString());
+        }
     }
 }