Add support for hiding the tab close button (#13348)

## Summary of the Pull Request

Adds support for the `tab.showCloseButton` property to themes. This accepts three values:

* `"always"` (default): The close button acts like it does today.
* `"hover"`: The close button is always visible on the active tab. On inactive tabs, the close button only appears on mouse over. 
* `"never"`: The close button is never visible. You can't close the tab with middle-click, but you can still use keyboard shortcuts to close the tab.

## References
* See #3327 
* ⚠️ targets #13178 ⚠️


## PR Checklist
* [x] Closes #3335
* [x] I work here
* [ ] Tests added/passed
* [n/a] Requires documentation to be updated - YUP

## Detailed Description of the Pull Request / Additional comments

See the following two properties in WInUI that we're leveraging here. 

* [`TabViewCloseButtonOverlayMode.OnPointerOver`](https://docs.microsoft.com/en-us/windows/winui/api/microsoft.ui.xaml.controls.tabviewclosebuttonoverlaymode?view=winui-2.7&viewFallbackFrom=winui-2.2)
* [`TabViewItem.IsClosable`](https://docs.microsoft.com/en-us/windows/winui/api/microsoft.ui.xaml.controls.tabviewitem.isclosable?view=winui-2.2#microsoft-ui-xaml-controls-tabviewitem-isclosable)

One is a tabview-level property, the other is a per-tab-item property, hence why this code is a little wacky. 

## Validation Steps Performed

gifs below

src/cascadia/TerminalApp/TabManagement.cpp

@@ -234,6 +234,9 @@ namespace winrt::TerminalApp::implementation
         auto tabViewItem = newTabImpl->TabViewItem();
         _tabView.TabItems().InsertAt(insertPosition, tabViewItem);
 
+        // Update the state of the close button to match the current theme
+        _updateTabCloseButton(tabViewItem);
+
         // Set this tab's icon to the icon from the user's profile
         if (const auto profile{ newTabImpl->GetFocusedProfile() })
         {

src/cascadia/TerminalApp/TerminalPage.cpp

@@ -225,6 +225,26 @@ namespace winrt::TerminalApp::implementation
         }
         _updateThemeColors();
 
+        // Initialize the state of the the CloseButtonOverlayMode property of
+        // our TabView, to match the tab.showCloseButton property in the theme.
+        if (const auto theme = _settings.GlobalSettings().CurrentTheme())
+        {
+            const auto visibility = theme.Tab() ? theme.Tab().ShowCloseButton() : Settings::Model::TabCloseButtonVisibility::Always;
+
+            switch (visibility)
+            {
+            case Settings::Model::TabCloseButtonVisibility::Never:
+                _tabView.CloseButtonOverlayMode(MUX::Controls::TabViewCloseButtonOverlayMode::Auto);
+                break;
+            case Settings::Model::TabCloseButtonVisibility::Hover:
+                _tabView.CloseButtonOverlayMode(MUX::Controls::TabViewCloseButtonOverlayMode::OnPointerOver);
+                break;
+            default:
+                _tabView.CloseButtonOverlayMode(MUX::Controls::TabViewCloseButtonOverlayMode::Always);
+                break;
+            }
+        }
+
         // Hookup our event handlers to the ShortcutActionDispatch
         _RegisterActionCallbacks();
 
@@ -2708,6 +2728,48 @@ namespace winrt::TerminalApp::implementation
         ////////////////////////////////////////////////////////////////////////
         // Begin Theme handling
         _updateThemeColors();
+
+        // Update the state of the the CloseButtonOverlayMode property of
+        // our TabView, to match the tab.showCloseButton property in the theme.
+        //
+        // Also update every tab's individual IsClosable to match.
+        //
+        // This is basically the same as _updateTabCloseButton, but with some
+        // code moved around to better facilitate updating every tab view item
+        // at once
+        if (const auto theme = _settings.GlobalSettings().CurrentTheme())
+        {
+            const auto visibility = theme.Tab() ? theme.Tab().ShowCloseButton() : Settings::Model::TabCloseButtonVisibility::Always;
+
+            for (const auto& tab : _tabs)
+            {
+                switch (visibility)
+                {
+                case Settings::Model::TabCloseButtonVisibility::Never:
+                    tab.TabViewItem().IsClosable(false);
+                    break;
+                case Settings::Model::TabCloseButtonVisibility::Hover:
+                    tab.TabViewItem().IsClosable(true);
+                    break;
+                default:
+                    tab.TabViewItem().IsClosable(true);
+                    break;
+                }
+            }
+
+            switch (visibility)
+            {
+            case Settings::Model::TabCloseButtonVisibility::Never:
+                _tabView.CloseButtonOverlayMode(MUX::Controls::TabViewCloseButtonOverlayMode::Auto);
+                break;
+            case Settings::Model::TabCloseButtonVisibility::Hover:
+                _tabView.CloseButtonOverlayMode(MUX::Controls::TabViewCloseButtonOverlayMode::OnPointerOver);
+                break;
+            default:
+                _tabView.CloseButtonOverlayMode(MUX::Controls::TabViewCloseButtonOverlayMode::Always);
+                break;
+            }
+        }
     }
 
     // This is a helper to aid in sorting commands by their `Name`s, alphabetically.
@@ -3261,6 +3323,9 @@ namespace winrt::TerminalApp::implementation
             auto tabViewItem = newTabImpl->TabViewItem();
             _tabView.TabItems().Append(tabViewItem);
 
+            // Update the state of the close button to match the current theme
+            _updateTabCloseButton(tabViewItem);
+
             tabViewItem.PointerPressed({ this, &TerminalPage::_OnTabClick });
 
             // When the tab requests close, try to close it (prompt for approval, if required)
@@ -4142,6 +4207,38 @@ namespace winrt::TerminalApp::implementation
         _SetNewTabButtonColor(bgColor, bgColor);
     }
 
+    void TerminalPage::_updateTabCloseButton(const winrt::Microsoft::UI::Xaml::Controls::TabViewItem& tabViewItem)
+    {
+        // Update the state of the close button to match the current theme.
+        // IMPORTANT: Should be called AFTER the tab view item is added to the TabView.
+        if (const auto theme = _settings.GlobalSettings().CurrentTheme())
+        {
+            const auto visibility = theme.Tab() ? theme.Tab().ShowCloseButton() : Settings::Model::TabCloseButtonVisibility::Always;
+
+            // Update both the tab item's IsClosable, but also the TabView's
+            // CloseButtonOverlayMode here. Because the TabViewItem was created
+            // outside the context of the TabView, it doesn't get the
+            // CloseButtonOverlayMode assigned on creation. We have to update
+            // that property again here, when we add the tab, so that the
+            // TabView will re-apply the value.
+            switch (visibility)
+            {
+            case Settings::Model::TabCloseButtonVisibility::Never:
+                tabViewItem.IsClosable(false);
+                _tabView.CloseButtonOverlayMode(MUX::Controls::TabViewCloseButtonOverlayMode::Auto);
+                break;
+            case Settings::Model::TabCloseButtonVisibility::Hover:
+                tabViewItem.IsClosable(true);
+                _tabView.CloseButtonOverlayMode(MUX::Controls::TabViewCloseButtonOverlayMode::OnPointerOver);
+                break;
+            default:
+                tabViewItem.IsClosable(true);
+                _tabView.CloseButtonOverlayMode(MUX::Controls::TabViewCloseButtonOverlayMode::Always);
+                break;
+            }
+        }
+    }
+
     void TerminalPage::WindowActivated(const bool activated)
     {
         // Stash if we're activated. Use that when we reload

src/cascadia/TerminalApp/TerminalPage.h

@@ -448,6 +448,7 @@ namespace winrt::TerminalApp::implementation
         static void _DismissMessage(const winrt::Microsoft::Terminal::Settings::Model::InfoBarMessage& message);
 
         void _updateThemeColors();
+        void _updateTabCloseButton(const winrt::Microsoft::UI::Xaml::Controls::TabViewItem& tabViewItem);
 
         winrt::fire_and_forget _ShowWindowChangedHandler(const IInspectable sender, const winrt::Microsoft::Terminal::Control::ShowWindowArgs args);
 

src/cascadia/TerminalSettingsModel/MTSMSettings.h

@@ -130,5 +130,6 @@ Author(s):
     X(winrt::Microsoft::Terminal::Settings::Model::ThemeColor, Background, "background", nullptr) \
     X(winrt::Microsoft::Terminal::Settings::Model::ThemeColor, UnfocusedBackground, "unfocusedBackground", nullptr)
 
-#define MTSM_THEME_TAB_SETTINGS(X) \
-    X(winrt::Microsoft::Terminal::Settings::Model::ThemeColor, Background, "background", nullptr)
+#define MTSM_THEME_TAB_SETTINGS(X)                                                                \
+    X(winrt::Microsoft::Terminal::Settings::Model::ThemeColor, Background, "background", nullptr) \
+    X(winrt::Microsoft::Terminal::Settings::Model::TabCloseButtonVisibility, ShowCloseButton, "showCloseButton", winrt::Microsoft::Terminal::Settings::Model::TabCloseButtonVisibility::Always)

src/cascadia/TerminalSettingsModel/TerminalSettingsSerializationHelpers.h

@@ -659,6 +659,15 @@ struct ::Microsoft::Terminal::Settings::Model::JsonUtils::ConversionTrait<winrt:
     }
 };
 
+JSON_ENUM_MAPPER(::winrt::Microsoft::Terminal::Settings::Model::TabCloseButtonVisibility)
+{
+    JSON_MAPPINGS(3) = {
+        pair_type{ "always", ValueType::Always },
+        pair_type{ "hover", ValueType::Hover },
+        pair_type{ "never", ValueType::Never },
+    };
+};
+
 // Possible ScrollToMarkDirection values
 JSON_ENUM_MAPPER(::winrt::Microsoft::Terminal::Control::ScrollToMarkDirection)
 {

src/cascadia/TerminalSettingsModel/Theme.idl

@@ -11,6 +11,13 @@ namespace Microsoft.Terminal.Settings.Model
         TerminalBackground
     };
 
+    enum TabCloseButtonVisibility
+    {
+        Always,
+        Hover,
+        Never
+    };
+
     runtimeclass ThemeColor
     {
         ThemeColor();
@@ -39,6 +46,7 @@ namespace Microsoft.Terminal.Settings.Model
 
     runtimeclass TabTheme {
         ThemeColor Background { get; };
+        TabCloseButtonVisibility ShowCloseButton { get; };
     }
 
     [default_interface] runtimeclass Theme : Windows.Foundation.IStringable {