Add support for access keys to Button.

samples/ControlCatalog/MainWindow.xaml

@@ -63,11 +63,11 @@
     <Panel Margin="{Binding #MainWindow.OffScreenMargin}">
       <DockPanel LastChildFill="True" Margin="{Binding #MainWindow.WindowDecorationMargin}">
         <Menu Name="MainMenu" DockPanel.Dock="Top">
-          <MenuItem Header="File">
-            <MenuItem Header="Exit" Command="{Binding ExitCommand}" />
+          <MenuItem Header="_File">
+            <MenuItem Header="E_xit" Command="{Binding ExitCommand}" />
           </MenuItem>
-          <MenuItem Header="Help">
-            <MenuItem Header="About" Command="{Binding AboutCommand}" />
+          <MenuItem Header="_Help">
+            <MenuItem Header="_About" Command="{Binding AboutCommand}" />
           </MenuItem>
         </Menu>
         <local:MainView />

samples/ControlCatalog/Pages/ButtonPage.xaml

@@ -10,7 +10,7 @@
                 HorizontalAlignment="Center"
                 Spacing="16">
       <StackPanel Orientation="Vertical" Spacing="8" Width="200">
-        <Button>Standard XAML Button</Button>
+        <Button>Standard _XAML Button</Button>
         <Button Foreground="White">Foreground</Button>
         <Button Background="{DynamicResource SystemAccentColor}">Background</Button>
         <Button IsEnabled="False">Disabled</Button>

samples/ControlCatalog/Pages/CheckBoxPage.xaml

@@ -11,9 +11,9 @@
                 Spacing="16">
       <StackPanel Orientation="Vertical"
                   Spacing="16">
-        <CheckBox>Unchecked</CheckBox>
-        <CheckBox IsChecked="True">Checked</CheckBox>
-        <CheckBox IsChecked="{x:Null}">Indeterminate</CheckBox>
+        <CheckBox>_Unchecked</CheckBox>
+        <CheckBox IsChecked="True">_Checked</CheckBox>
+        <CheckBox IsChecked="{x:Null}">_Indeterminate</CheckBox>
         <CheckBox IsChecked="True" IsEnabled="False">Disabled</CheckBox>
       </StackPanel>
       <StackPanel Orientation="Vertical"

samples/ControlCatalog/Pages/DialogsPage.xaml

@@ -3,15 +3,15 @@
              x:Class="ControlCatalog.Pages.DialogsPage">
   <StackPanel Orientation="Vertical" Spacing="4" Margin="4">
       <CheckBox Name="UseFilters">Use filters</CheckBox>
-      <Button Name="OpenFile">Open File</Button>
-      <Button Name="SaveFile">Save File</Button>
-      <Button Name="SelectFolder">Select Folder</Button>
-      <Button Name="OpenBoth">Select Both</Button>
-      <Button Name="DecoratedWindow">Decorated window</Button>
-      <Button Name="DecoratedWindowDialog">Decorated window (dialog)</Button>
-      <Button Name="Dialog">Dialog</Button>
-      <Button Name="DialogNoTaskbar">Dialog (No taskbar icon)</Button>
-      <Button Name="OwnedWindow">Owned window</Button>
-      <Button Name="OwnedWindowNoTaskbar">Owned window (No taskbar icon)</Button>
+      <Button Name="OpenFile">_Open File</Button>
+      <Button Name="SaveFile">_Save File</Button>
+      <Button Name="SelectFolder">Select Fo_lder</Button>
+      <Button Name="OpenBoth">Select _Both</Button>
+      <Button Name="DecoratedWindow">Decorated _window</Button>
+      <Button Name="DecoratedWindowDialog">Decorated w_indow (dialog)</Button>
+      <Button Name="Dialog">_Dialog</Button>
+      <Button Name="DialogNoTaskbar">Dialog (_No taskbar icon)</Button>
+      <Button Name="OwnedWindow">Own_ed window</Button>
+      <Button Name="OwnedWindowNoTaskbar">Owned window (No tas_kbar icon)</Button>
   </StackPanel>
 </UserControl>

samples/ControlCatalog/Pages/RadioButtonPage.xaml

@@ -11,9 +11,9 @@
                 Spacing="16">
       <StackPanel Orientation="Vertical"
                   Spacing="16">
-        <RadioButton IsChecked="True">Option 1</RadioButton>
-        <RadioButton>Option 2</RadioButton>
-        <RadioButton IsChecked="{x:Null}">Option 3</RadioButton>
+        <RadioButton IsChecked="True">_Option 1</RadioButton>
+        <RadioButton>O_ption 2</RadioButton>
+        <RadioButton IsChecked="{x:Null}">Op_tion 3</RadioButton>
         <RadioButton IsEnabled="False">Disabled</RadioButton>
       </StackPanel>
       <StackPanel Orientation="Vertical"

samples/ControlCatalog/Pages/ToggleSwitchPage.xaml

@@ -14,7 +14,7 @@
 
     <Border Classes="Thin">
       <StackPanel>
-        <ToggleSwitch Content="headered" IsChecked="true" Margin="10"/>
+        <ToggleSwitch Content="h_eadered" IsChecked="true" Margin="10"/>
         <TextBox Classes="CodeBox"
           Text="&lt;ToggleSwitch&gt;headered&lt;/ToggleSwitch&gt;"/>
       </StackPanel>
@@ -24,7 +24,7 @@
 
     <Border Classes="Thin">
       <StackPanel>
-        <ToggleSwitch Content="Custom"
+        <ToggleSwitch Content="_Custom"
           OnContent="On"
           OffContent="Off"
           Margin="10"/>
@@ -40,7 +40,7 @@ ContentOff=&quot;Off&quot; /&gt;"
 
     <Border Classes="Thin">
       <StackPanel>
-        <ToggleSwitch Content="Just Click!" Margin="10">
+        <ToggleSwitch Content="_Just Click!" Margin="10">
           <ToggleSwitch.OnContent>
             <Image Source="/Assets/hirsch-899118_640.jpg" Height="32"/>
           </ToggleSwitch.OnContent>

src/Avalonia.Controls/Button.cs

@@ -99,6 +99,7 @@ static Button()
             CommandParameterProperty.Changed.Subscribe(CommandParameterChanged);
             IsDefaultProperty.Changed.Subscribe(IsDefaultChanged);
             IsCancelProperty.Changed.Subscribe(IsCancelChanged);
+            AccessKeyHandler.AccessKeyPressedEvent.AddClassHandler<Button>((lbl, args) => lbl.OnAccessKey(args));
         }
 
         public Button()
@@ -256,6 +257,8 @@ protected override void OnDetachedFromLogicalTree(LogicalTreeAttachmentEventArgs
             }
         }
 
+        protected virtual void OnAccessKey(RoutedEventArgs e) => OnClick();
+
         /// <inheritdoc/>
         protected override void OnKeyDown(KeyEventArgs e)
         {

src/Avalonia.Controls/Primitives/AccessText.cs

@@ -68,7 +68,7 @@ public override void Render(DrawingContext context)
             if (underscore != -1 && ShowAccessKey)
             {
                 var rect = TextLayout.HitTestTextPosition(underscore);
-                var offset = new Vector(0, -0.5);
+                var offset = new Vector(0, -1.5);
                 context.DrawLine(
                     new Pen(Foreground, 1),
                     rect.BottomLeft + offset,

src/Avalonia.Themes.Default/Button.xaml

@@ -17,6 +17,7 @@
                           ContentTemplate="{TemplateBinding ContentTemplate}"
                           Content="{TemplateBinding Content}"
                           Padding="{TemplateBinding Padding}"
+                          RecognizesAccessKey="True"
                           TextBlock.Foreground="{TemplateBinding Foreground}"
                           HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
                           VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"/>

src/Avalonia.Themes.Default/CheckBox.xaml

@@ -41,6 +41,7 @@
                             ContentTemplate="{TemplateBinding ContentTemplate}"
                             Content="{TemplateBinding Content}"
                             Margin="{TemplateBinding Padding}"
+                            RecognizesAccessKey="True"
                             VerticalAlignment="{TemplateBinding VerticalContentAlignment}"
                             HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
                             IsVisible="{TemplateBinding Content, Converter={x:Static ObjectConverters.IsNotNull}}"

src/Avalonia.Themes.Default/RadioButton.xaml

@@ -31,6 +31,7 @@
                             ContentTemplate="{TemplateBinding ContentTemplate}"
                             Content="{TemplateBinding Content}"
                             Margin="4,0,0,0"
+                            RecognizesAccessKey="True"
                             VerticalAlignment="Center"
                             Grid.Column="1"/>
         </Grid>

src/Avalonia.Themes.Default/ToggleButton.xaml

@@ -17,6 +17,7 @@
                           ContentTemplate="{TemplateBinding ContentTemplate}"
                           Content="{TemplateBinding Content}"
                           Padding="{TemplateBinding Padding}"
+                          RecognizesAccessKey="True"
                           TextBlock.Foreground="{TemplateBinding Foreground}"
                           HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
                           VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"/>

src/Avalonia.Themes.Default/ToggleSwitch.xaml

@@ -87,6 +87,7 @@
             Grid.Row="0"
             Content="{TemplateBinding Content}"
             ContentTemplate="{TemplateBinding ContentTemplate}"
+            RecognizesAccessKey="True"
             VerticalAlignment="Top"/>
 
           <Grid Grid.Row="1"

src/Avalonia.Themes.Fluent/Controls/Button.xaml

@@ -34,6 +34,7 @@
                           Content="{TemplateBinding Content}"
                           ContentTemplate="{TemplateBinding ContentTemplate}"
                           Padding="{TemplateBinding Padding}"
+                          RecognizesAccessKey="True"
                           HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
                           VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}" />
       </ControlTemplate>

src/Avalonia.Themes.Fluent/Controls/CheckBox.xaml

@@ -44,6 +44,7 @@
                          ContentTemplate="{TemplateBinding ContentTemplate}"
                          Content="{TemplateBinding Content}"
                          Margin="{TemplateBinding Padding}"
+                         RecognizesAccessKey="True"
                          HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
                          VerticalAlignment="{TemplateBinding VerticalContentAlignment}"
                          Grid.Column="1" />

src/Avalonia.Themes.Fluent/Controls/RadioButton.xaml

@@ -51,6 +51,7 @@
                               ContentTemplate="{TemplateBinding ContentTemplate}"
                               TextBlock.Foreground="{TemplateBinding Foreground}"
                               Margin="{TemplateBinding Padding}"
+                              RecognizesAccessKey="True"
                               HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
                               VerticalAlignment="{TemplateBinding VerticalContentAlignment}"
                               Grid.Column="1" />

src/Avalonia.Themes.Fluent/Controls/ToggleButton.xaml

@@ -34,6 +34,7 @@
                           Content="{TemplateBinding Content}"
                           ContentTemplate="{TemplateBinding ContentTemplate}"
                           Padding="{TemplateBinding Padding}"
+                          RecognizesAccessKey="True"
                           HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
                           VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}" />
       </ControlTemplate>

src/Avalonia.Themes.Fluent/Controls/ToggleSwitch.xaml

@@ -53,6 +53,7 @@
             Grid.Row="0"
             Content="{TemplateBinding Content}"
             ContentTemplate="{TemplateBinding ContentTemplate}"
+            RecognizesAccessKey="True"
             VerticalAlignment="Top"/>
 
           <Grid Grid.Row="1"

tests/Avalonia.Controls.UnitTests/ButtonTests.cs

@@ -2,6 +2,7 @@
 using System.Windows.Input;
 using Avalonia.Data;
 using Avalonia.Input;
+using Avalonia.Interactivity;
 using Avalonia.Media;
 using Avalonia.Platform;
 using Avalonia.Rendering;
@@ -271,6 +272,19 @@ public void Button_Unsubscribes_From_Command_CanExecuteChanged_When_Removed_From
 
         [Fact]
         public void Button_Invokes_CanExecute_When_CommandParameter_Changed()
+        {
+            var target = new Button();
+            var raised = 0;
+
+            target.Click += (s, e) => ++raised;
+
+            target.RaiseEvent(new RoutedEventArgs(AccessKeyHandler.AccessKeyPressedEvent));
+
+            Assert.Equal(1, raised);
+        }
+
+        [Fact]
+        public void Raises_Click_When_AccessKey_Raised()
         {
             var command = new TestCommand(p => p is bool value && value);
             var target = new Button { Command = command };