Enable moving back to the root level in the command palette (#8051)

This commit adds functionality so that users can move back from sub menu
whenever they want. As a result, users no longer have to close command
palette and open it again to get all commands again.

Closes #7910

Author: kaihugo

src/cascadia/TerminalApp/CommandPalette.cpp

@@ -428,6 +428,25 @@ namespace winrt::TerminalApp::implementation
         _dispatchCommand(e.ClickedItem().try_as<Command>());
     }
 
+    // Method Description:
+    // This event is called when the user clicks on an ChevronLeft button right
+    // next to the ParentCommandName (e.g. New Tab...) above the subcommands list.
+    // It'll go up a level when the users click the button.
+    // Arguments:
+    // - sender: the button that got clicked
+    // Return Value:
+    // - <none>
+    void CommandPalette::_moveBackButtonClicked(Windows::Foundation::IInspectable const& /*sender*/,
+                                                Windows::UI::Xaml::RoutedEventArgs const&)
+    {
+        _nestedActionStack.Clear();
+        ParentCommandName(L"");
+        _currentNestedCommands.Clear();
+        _searchBox().Focus(FocusState::Programmatic);
+        _updateFilteredActions();
+        _filteredActionsView().SelectedIndex(0);
+    }
+
     // Method Description:
     // - This is called when the user selects a command with subcommands. It
     //   will update our UI to now display the list of subcommands instead, and

src/cascadia/TerminalApp/CommandPalette.h

@@ -81,6 +81,8 @@ namespace winrt::TerminalApp::implementation
 
         void _listItemClicked(Windows::Foundation::IInspectable const& sender, Windows::UI::Xaml::Controls::ItemClickEventArgs const& e);
 
+        void _moveBackButtonClicked(Windows::Foundation::IInspectable const& sender, Windows::UI::Xaml::RoutedEventArgs const&);
+
         void _updateFilteredActions();
 
         std::vector<Microsoft::Terminal::Settings::Model::Command> _collectFilteredActions();

src/cascadia/TerminalApp/CommandPalette.xaml

@@ -186,16 +186,36 @@ the MIT License. See LICENSE in the project root for license information. -->
                 >
             </TextBlock>
 
-            <TextBlock
-                Padding="16, 0, 16, 4"
-                x:Name="_parentCommandText"
-                FontStyle="Italic"
-                Visibility="{x:Bind ParentCommandName,
-                             Mode=OneWay,
-                             Converter={StaticResource ParentCommandVisibilityConverter}}"
-                Grid.Row="1"
-                Text="{x:Bind ParentCommandName, Mode=OneWay}">
-            </TextBlock>
+          <StackPanel Orientation="Horizontal"
+                    Padding="16, 0, 16, 4"
+                    Grid.Row="1"
+                    Visibility="{x:Bind ParentCommandName,
+                                 Mode=OneWay,
+                                 Converter={StaticResource ParentCommandVisibilityConverter}}">
+
+                <Button
+                    Background="Transparent"
+                    x:Name="_parentCommandBackButton"
+                    x:Uid="ParentCommandBackButton"
+                    Click="_moveBackButtonClicked"
+                    ClickMode="Press"
+                    VerticalAlignment="Center">
+                    <FontIcon 
+                        FontSize="12"
+                        FontFamily="Segoe MDL2 Assets" 
+                        Glyph="&#xE76b;">
+                    </FontIcon>
+                </Button>
+
+                <TextBlock
+                    Padding="16, 0, 16, 4"
+                    x:Name="_parentCommandText"
+                    FontStyle="Italic"
+                    Grid.Row="1"
+                    Text="{x:Bind ParentCommandName, Mode=OneWay}"
+                    VerticalAlignment="Center">
+                </TextBlock>
+            </StackPanel>
 
             <TextBlock
                 Padding="16"

src/cascadia/TerminalApp/Resources/en-US/Resources.resw

@@ -482,4 +482,10 @@
   <data name="FailedToWriteToSettings" xml:space="preserve">
     <value>We could not write to your settings file. Check the permissions on that file to ensure that the read-only flag is not set and that write access is granted.</value>
   </data>
+  <data name="ParentCommandBackButton.[using:Windows.UI.Xaml.Automation]AutomationProperties.Name" xml:space="preserve">
+    <value>Back</value>
+  </data>
+  <data name="ParentCommandBackButton.[using:Windows.UI.Xaml.Controls]ToolTipService.ToolTip" xml:space="preserve">
+    <value>Back</value>
+  </data>
 </root>