microsoft · DHowett · Apr 20, 2023 · Apr 18, 2023
diff --git a/src/cascadia/TerminalApp/App.xaml b/src/cascadia/TerminalApp/App.xaml
@@ -5,10 +5,10 @@
 <Application x:Class="TerminalApp.App"
              xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
-             xmlns:TA="using:TerminalApp"
              xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
              xmlns:local="using:TerminalApp"
              xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+             xmlns:primitives="using:Microsoft.UI.Xaml.Controls.Primitives"
              mc:Ignorable="d">
     <!--
         If you want to prove this works, then add `RequestedTheme="Light"` to
@@ -48,6 +48,23 @@
                     <Thickness x:Key="TabViewHeaderPadding">9,0,5,0</Thickness>
                     <Thickness x:Key="TabViewItemBorderThickness">1,1,1,0</Thickness>
 
+                    <!--
+                        Disable the EntranceThemeTransition for our muxc:TabView, which would slowly slide in the tabs
+                        while the window opens. The difference is especially noticeable if window fade-in transitions are
+                        disabled system-wide. On my system this shaves off about 10% of the startup cost and looks better.
+                    -->
+                    <Style TargetType="primitives:TabViewListView">
+                        <Setter Property="ItemContainerTransitions">
+                            <Setter.Value>
+                                <TransitionCollection>
+                                    <AddDeleteThemeTransition />
+                                    <ContentThemeTransition />
+                                    <ReorderThemeTransition />
+                                </TransitionCollection>
+                            </Setter.Value>
+                        </Setter>
+                    </Style>
+
                     <!--  Shadow that can be used by any control.  -->
                     <ThemeShadow x:Name="SharedShadow" />
 

diff --git a/src/cascadia/TerminalApp/SettingsTab.cpp b/src/cascadia/TerminalApp/SettingsTab.cpp
@@ -21,6 +21,8 @@ namespace winrt
     namespace WUX = Windows::UI::Xaml;
 }
 
+#define ASSERT_UI_THREAD() assert(TabViewItem().Dispatcher().HasThreadAccess())
+
 namespace winrt::TerminalApp::implementation
 {
     SettingsTab::SettingsTab(MainPage settingsUI,
@@ -36,6 +38,8 @@ namespace winrt::TerminalApp::implementation
 
     void SettingsTab::UpdateSettings(CascadiaSettings settings)
     {
+        ASSERT_UI_THREAD();
+
         auto settingsUI{ Content().as<MainPage>() };
         settingsUI.UpdateSettings(settings);
 
@@ -55,6 +59,8 @@ namespace winrt::TerminalApp::implementation
     // - The list of actions.
     std::vector<ActionAndArgs> SettingsTab::BuildStartupActions(const bool /*asContent*/) const
     {
+        ASSERT_UI_THREAD();
+
         ActionAndArgs action;
         action.Action(ShortcutAction::OpenSettings);
         OpenSettingsArgs args{ SettingsTarget::SettingsUI };
@@ -71,6 +77,8 @@ namespace winrt::TerminalApp::implementation
     // - <none>
     void SettingsTab::Focus(WUX::FocusState focusState)
     {
+        ASSERT_UI_THREAD();
+
         _focusState = focusState;
 
         if (_focusState != FocusState::Unfocused)
@@ -99,20 +107,14 @@ namespace winrt::TerminalApp::implementation
     // - <none>
     // Return Value:
     // - <none>
-    winrt::fire_and_forget SettingsTab::_CreateIcon()
+    void SettingsTab::_CreateIcon()
     {
-        auto weakThis{ get_weak() };
+        // This is the Setting icon (looks like a gear)
+        static constexpr std::wstring_view glyph{ L"\xE713" };
 
-        co_await wil::resume_foreground(TabViewItem().Dispatcher());
-
-        if (auto tab{ weakThis.get() })
-        {
-            auto glyph = L"\xE713"; // This is the Setting icon (looks like a gear)
-
-            // The TabViewItem Icon needs MUX while the IconSourceElement in the CommandPalette needs WUX...
-            Icon(glyph);
-            TabViewItem().IconSource(IconPathConverter::IconSourceMUX(glyph));
-        }
+        // The TabViewItem Icon needs MUX while the IconSourceElement in the CommandPalette needs WUX...
+        Icon(winrt::hstring{ glyph });
+        TabViewItem().IconSource(IconPathConverter::IconSourceMUX(glyph));
     }
 
     winrt::Windows::UI::Xaml::Media::Brush SettingsTab::_BackgroundBrush()

diff --git a/src/cascadia/TerminalApp/SettingsTab.h b/src/cascadia/TerminalApp/SettingsTab.h
@@ -36,7 +36,7 @@ namespace winrt::TerminalApp::implementation
         winrt::Windows::UI::Xaml::ElementTheme _requestedTheme;
 
         void _MakeTabViewItem() override;
-        winrt::fire_and_forget _CreateIcon();
+        void _CreateIcon();
 
         virtual winrt::Windows::UI::Xaml::Media::Brush _BackgroundBrush() override;
     };

diff --git a/src/cascadia/TerminalApp/TabBase.cpp b/src/cascadia/TerminalApp/TabBase.cpp
@@ -21,6 +21,8 @@ namespace winrt
     namespace WUX = Windows::UI::Xaml;
 }
 
+#define ASSERT_UI_THREAD() assert(TabViewItem().Dispatcher().HasThreadAccess())
+
 namespace winrt::TerminalApp::implementation
 {
     WUX::FocusState TabBase::FocusState() const noexcept
@@ -32,6 +34,8 @@ namespace winrt::TerminalApp::implementation
     // - Prepares this tab for being removed from the UI hierarchy
     void TabBase::Shutdown()
     {
+        ASSERT_UI_THREAD();
+
         Content(nullptr);
         _ClosedHandlers(nullptr, nullptr);
     }
@@ -159,6 +163,8 @@ namespace winrt::TerminalApp::implementation
 
     void TabBase::UpdateTabViewIndex(const uint32_t idx, const uint32_t numTabs)
     {
+        ASSERT_UI_THREAD();
+
         TabViewIndex(idx);
         TabViewNumTabs(numTabs);
         _EnableCloseMenuItems();
@@ -167,11 +173,15 @@ namespace winrt::TerminalApp::implementation
 
     void TabBase::SetDispatch(const winrt::TerminalApp::ShortcutActionDispatch& dispatch)
     {
+        ASSERT_UI_THREAD();
+
         _dispatch = dispatch;
     }
 
     void TabBase::SetActionMap(const Microsoft::Terminal::Settings::Model::IActionMapView& actionMap)
     {
+        ASSERT_UI_THREAD();
+
         _actionMap = actionMap;
         _UpdateSwitchToTabKeyChord();
     }
@@ -183,26 +193,18 @@ namespace winrt::TerminalApp::implementation
     // - keyChord - string representation of the key chord that switches to the current tab
     // Return Value:
     // - <none>
-    winrt::fire_and_forget TabBase::_UpdateSwitchToTabKeyChord()
+    void TabBase::_UpdateSwitchToTabKeyChord()
     {
         const auto keyChord = _actionMap ? _actionMap.GetKeyBindingForAction(ShortcutAction::SwitchToTab, SwitchToTabArgs{ _TabViewIndex }) : nullptr;
         const auto keyChordText = keyChord ? KeyChordSerialization::ToString(keyChord) : L"";
 
         if (_keyChord == keyChordText)
         {
-            co_return;
+            return;
         }
 
         _keyChord = keyChordText;
-
-        auto weakThis{ get_weak() };
-
-        co_await wil::resume_foreground(TabViewItem().Dispatcher());
-
-        if (auto tab{ weakThis.get() })
-        {
-            _UpdateToolTip();
-        }
+        _UpdateToolTip();
     }
 
     // Method Description:
@@ -281,13 +283,17 @@ namespace winrt::TerminalApp::implementation
 
     std::optional<winrt::Windows::UI::Color> TabBase::GetTabColor()
     {
+        ASSERT_UI_THREAD();
+
         return std::nullopt;
     }
 
     void TabBase::ThemeColor(const winrt::Microsoft::Terminal::Settings::Model::ThemeColor& focused,
                              const winrt::Microsoft::Terminal::Settings::Model::ThemeColor& unfocused,
                              const til::color& tabRowColor)
     {
+        ASSERT_UI_THREAD();
+
         _themeColor = focused;
         _unfocusedThemeColor = unfocused;
         _tabRowColor = tabRowColor;
@@ -305,49 +311,37 @@ namespace winrt::TerminalApp::implementation
     // - <none>
     void TabBase::_RecalculateAndApplyTabColor()
     {
-        auto weakThis{ get_weak() };
-
-        TabViewItem().Dispatcher().RunAsync(CoreDispatcherPriority::Normal, [weakThis]() {
-            auto ptrTab = weakThis.get();
-            if (!ptrTab)
-            {
-                return;
-            }
-
-            auto tab{ ptrTab };
+        // GetTabColor will return the color set by the color picker, or the
+        // color specified in the profile. If neither of those were set,
+        // then look to _themeColor to see if there's a value there.
+        // Otherwise, clear our color, falling back to the TabView defaults.
+        const auto currentColor = GetTabColor();
+        if (currentColor.has_value())
+        {
+            _ApplyTabColorOnUIThread(currentColor.value());
+        }
+        else if (_themeColor != nullptr)
+        {
+            // Safely get the active control's brush.
+            const Media::Brush terminalBrush{ _BackgroundBrush() };
 
-            // GetTabColor will return the color set by the color picker, or the
-            // color specified in the profile. If neither of those were set,
-            // then look to _themeColor to see if there's a value there.
-            // Otherwise, clear our color, falling back to the TabView defaults.
-            const auto currentColor = tab->GetTabColor();
-            if (currentColor.has_value())
+            if (const auto themeBrush{ _themeColor.Evaluate(Application::Current().Resources(), terminalBrush, false) })
             {
-                tab->_ApplyTabColorOnUIThread(currentColor.value());
-            }
-            else if (tab->_themeColor != nullptr)
-            {
-                // Safely get the active control's brush.
-                const Media::Brush terminalBrush{ tab->_BackgroundBrush() };
-
-                if (const auto themeBrush{ tab->_themeColor.Evaluate(Application::Current().Resources(), terminalBrush, false) })
-                {
-                    // ThemeColor.Evaluate will get us a Brush (because the
-                    // TermControl could have an acrylic BG, for example). Take
-                    // that brush, and get the color out of it. We don't really
-                    // want to have the tab items themselves be acrylic.
-                    tab->_ApplyTabColorOnUIThread(til::color{ ThemeColor::ColorFromBrush(themeBrush) });
-                }
-                else
-                {
-                    tab->_ClearTabBackgroundColor();
-                }
+                // ThemeColor.Evaluate will get us a Brush (because the
+                // TermControl could have an acrylic BG, for example). Take
+                // that brush, and get the color out of it. We don't really
+                // want to have the tab items themselves be acrylic.
+                _ApplyTabColorOnUIThread(til::color{ ThemeColor::ColorFromBrush(themeBrush) });
             }
             else
             {
-                tab->_ClearTabBackgroundColor();
+                _ClearTabBackgroundColor();
             }
-        });
+        }
+        else
+        {
+            _ClearTabBackgroundColor();
+        }
     }
 
     // Method Description:

diff --git a/src/cascadia/TerminalApp/TabBase.h b/src/cascadia/TerminalApp/TabBase.h
@@ -69,7 +69,7 @@ namespace winrt::TerminalApp::implementation
         void _EnableCloseMenuItems();
         void _CloseTabsAfter();
         void _CloseOtherTabs();
-        winrt::fire_and_forget _UpdateSwitchToTabKeyChord();
+        void _UpdateSwitchToTabKeyChord();
         void _UpdateToolTip();
 
         void _RecalculateAndApplyTabColor();