Remove Monarch/Peasant & Make UI single-threaded

src/cascadia/TerminalControl/TermControl.cpp

@@ -58,7 +58,7 @@ DEFINE_ENUM_FLAG_OPERATORS(winrt::Microsoft::Terminal::Control::MouseButtonState
 static void hideCursorUntilMoved()
 {
     static CoreCursor previousCursor{ nullptr };
-    static auto shouldVanish = []() {
+    static const auto shouldVanish = []() {
         BOOL shouldVanish = TRUE;
         SystemParametersInfoW(SPI_GETMOUSEVANISH, 0, &shouldVanish, 0);
         if (!shouldVanish)

src/cascadia/WindowsTerminal/AppHost.cpp

@@ -27,17 +27,27 @@ using namespace std::chrono_literals;
 static constexpr short KeyPressed{ gsl::narrow_cast<short>(0x8000) };
 static constexpr auto FrameUpdateInterval = std::chrono::milliseconds(16);
 
-static winrt::com_ptr<IVirtualDesktopManager> s_desktopManager;
+winrt::com_ptr<IVirtualDesktopManager> getDesktopManager()
+{
+    static til::shared_mutex<winrt::com_ptr<IVirtualDesktopManager>> s_desktopManager;
+
+    if (const auto manager = *s_desktopManager.lock_shared())
+    {
+        return manager;
+    }
+
+    const auto guard = s_desktopManager.lock();
+    if (!*guard)
+    {
+        *guard = winrt::try_create_instance<IVirtualDesktopManager>(__uuidof(VirtualDesktopManager));
+    }
+    return *guard;
+}
 
 AppHost::AppHost(WindowEmperor* manager, const winrt::TerminalApp::AppLogic& logic, winrt::TerminalApp::WindowRequestedArgs args) noexcept :
     _appLogic{ logic },
     _windowManager{ manager }
 {
-    if (!s_desktopManager)
-    {
-        s_desktopManager = winrt::try_create_instance<IVirtualDesktopManager>(__uuidof(VirtualDesktopManager));
-    }
-
     _HandleCommandlineArgs(args);
 
     // _HandleCommandlineArgs will create a _windowLogic
@@ -327,8 +337,9 @@ winrt::Windows::Foundation::IAsyncOperation<winrt::guid> AppHost::GetVirtualDesk
     const auto dispatcher = _windowLogic.GetRoot().Dispatcher();
     const auto hwnd = _window->GetHandle();
     const auto weakThis = weak_from_this();
+    const auto desktopManager = getDesktopManager();
 
-    if (!hwnd || !s_desktopManager)
+    if (!hwnd || !desktopManager)
     {
         co_return null_guid;
     }
@@ -339,7 +350,7 @@ winrt::Windows::Foundation::IAsyncOperation<winrt::guid> AppHost::GetVirtualDesk
     co_await winrt::resume_background();
 
     GUID id;
-    if (FAILED_LOG(s_desktopManager->GetWindowDesktopId(hwnd, &id)))
+    if (FAILED_LOG(desktopManager->GetWindowDesktopId(hwnd, &id)))
     {
         co_return null_guid;
     }
@@ -811,37 +822,47 @@ void AppHost::_WindowActivated(bool activated)
     }
 }
 
-void AppHost::HandleSummon(const winrt::TerminalApp::SummonWindowBehavior args) const
+safe_void_coroutine AppHost::HandleSummon(const winrt::TerminalApp::SummonWindowBehavior args) const
 {
     _window->SummonWindow(args);
 
-    if (args != nullptr && args.MoveToCurrentDesktop())
+    if (!args || !args.MoveToCurrentDesktop())
     {
-        if (s_desktopManager)
-        {
-            // First thing - make sure that we're not on the current desktop. If
-            // we are, then don't call MoveWindowToDesktop. This is to mitigate
-            // MSFT:33035972
-            BOOL onCurrentDesktop{ false };
-            if (SUCCEEDED(s_desktopManager->IsWindowOnCurrentVirtualDesktop(_window->GetHandle(), &onCurrentDesktop)) && onCurrentDesktop)
-            {
-                // If we succeeded, and the window was on the current desktop, then do nothing.
-            }
-            else
-            {
-                // Here, we either failed to check if the window is on the
-                // current desktop, or it wasn't on that desktop. In both those
-                // cases, just move the window.
+        co_return;
+    }
 
-                GUID currentlyActiveDesktop{ 0 };
-                if (VirtualDesktopUtils::GetCurrentVirtualDesktopId(&currentlyActiveDesktop))
-                {
-                    LOG_IF_FAILED(s_desktopManager->MoveWindowToDesktop(_window->GetHandle(), currentlyActiveDesktop));
-                }
-                // If GetCurrentVirtualDesktopId failed, then just leave the window
-                // where it is. Nothing else to be done :/
-            }
+    const auto desktopManager = getDesktopManager();
+    if (!desktopManager)
+    {
+        co_return;
+    }
+
+    // Just like AppHost::GetVirtualDesktopId:
+    // IVirtualDesktopManager is cross-process COM into explorer.exe,
+    // and we can't use that on the UI thread.
+    co_await winrt::resume_background();
+
+    // First thing - make sure that we're not on the current desktop. If
+    // we are, then don't call MoveWindowToDesktop. This is to mitigate
+    // MSFT:33035972
+    BOOL onCurrentDesktop{ false };
+    if (SUCCEEDED(desktopManager->IsWindowOnCurrentVirtualDesktop(_window->GetHandle(), &onCurrentDesktop)) && onCurrentDesktop)
+    {
+        // If we succeeded, and the window was on the current desktop, then do nothing.
+    }
+    else
+    {
+        // Here, we either failed to check if the window is on the
+        // current desktop, or it wasn't on that desktop. In both those
+        // cases, just move the window.
+
+        GUID currentlyActiveDesktop{ 0 };
+        if (VirtualDesktopUtils::GetCurrentVirtualDesktopId(&currentlyActiveDesktop))
+        {
+            LOG_IF_FAILED(desktopManager->MoveWindowToDesktop(_window->GetHandle(), currentlyActiveDesktop));
         }
+        // If GetCurrentVirtualDesktopId failed, then just leave the window
+        // where it is. Nothing else to be done :/
     }
 }
 
@@ -1037,12 +1058,12 @@ void AppHost::_WindowSizeChanged(const winrt::Windows::Foundation::IInspectable&
 void AppHost::_SummonWindowRequested(const winrt::Windows::Foundation::IInspectable&,
                                      const winrt::Windows::Foundation::IInspectable&)
 {
-    const winrt::TerminalApp::SummonWindowBehavior summonArgs{};
+    winrt::TerminalApp::SummonWindowBehavior summonArgs;
     summonArgs.MoveToCurrentDesktop(false);
     summonArgs.DropdownDuration(0);
     summonArgs.ToMonitor(winrt::TerminalApp::MonitorBehavior::InPlace);
     summonArgs.ToggleVisibility(false); // Do not toggle, just make visible.
-    HandleSummon(summonArgs);
+    HandleSummon(std::move(summonArgs));
 }
 
 void AppHost::_OpenSystemMenu(const winrt::Windows::Foundation::IInspectable&,

src/cascadia/WindowsTerminal/AppHost.h

@@ -24,7 +24,7 @@ class AppHost : public std::enable_shared_from_this<AppHost>
 
     bool OnDirectKeyEvent(uint32_t vkey, uint8_t scanCode, bool down);
     void SetTaskbarProgress(const winrt::Windows::Foundation::IInspectable& sender, const winrt::Windows::Foundation::IInspectable& args);
-    void HandleSummon(winrt::TerminalApp::SummonWindowBehavior args) const;
+    safe_void_coroutine HandleSummon(winrt::TerminalApp::SummonWindowBehavior args) const;
     void DispatchCommandline(winrt::TerminalApp::CommandlineArgs args);
 
 private:

src/cascadia/WindowsTerminal/WindowEmperor.cpp

@@ -642,20 +642,17 @@ static WindowEmperor* GetThisFromHandle(HWND const window) noexcept
 
 [[nodiscard]] LRESULT __stdcall WindowEmperor::_wndProc(HWND const window, UINT const message, WPARAM const wparam, LPARAM const lparam) noexcept
 {
-    WINRT_ASSERT(window);
+    if (const auto that = GetThisFromHandle(window))
+    {
+        return that->_messageHandler(window, message, wparam, lparam);
+    }
 
     if (WM_NCCREATE == message)
     {
         const auto cs = reinterpret_cast<CREATESTRUCT*>(lparam);
-        WindowEmperor* that = static_cast<WindowEmperor*>(cs->lpCreateParams);
-        WINRT_ASSERT(that);
-        WINRT_ASSERT(!that->_window);
-        that->_window = wil::unique_hwnd(window);
-        SetWindowLongPtr(that->_window.get(), GWLP_USERDATA, reinterpret_cast<LONG_PTR>(that));
-    }
-    else if (WindowEmperor* that = GetThisFromHandle(window))
-    {
-        return that->_messageHandler(window, message, wparam, lparam);
+        const auto that = static_cast<WindowEmperor*>(cs->lpCreateParams);
+        that->_window.reset(window);
+        SetWindowLongPtrW(window, GWLP_USERDATA, reinterpret_cast<LONG_PTR>(that));
     }
 
     return DefWindowProcW(window, message, wparam, lparam);
@@ -674,6 +671,12 @@ void WindowEmperor::_createMessageWindow(const wchar_t* className)
     };
     RegisterClassW(&wc);
 
+    WM_TASKBARCREATED = RegisterWindowMessageW(L"TaskbarCreated");
+
+    // NOTE: This cannot be a HWND_MESSAGE window as otherwise we don't
+    // receive any HWND_BROADCAST messages, like WM_QUERYENDSESSION.
+    // NOTE: Before CreateWindowExW() returns it invokes our WM_NCCREATE
+    // message handler, which then stores the HWND in this->_window.
     WINRT_VERIFY(CreateWindowExW(
         /* dwExStyle    */ 0,
         /* lpClassName  */ className,
@@ -683,7 +686,7 @@ void WindowEmperor::_createMessageWindow(const wchar_t* className)
         /* Y            */ 0,
         /* nWidth       */ 0,
         /* nHeight      */ 0,
-        /* hWndParent   */ HWND_MESSAGE,
+        /* hWndParent   */ nullptr,
         /* hMenu        */ nullptr,
         /* hInstance    */ instance,
         /* lpParam      */ this));
@@ -724,10 +727,6 @@ safe_void_coroutine WindowEmperor::_showMessageBox(winrt::hstring message, bool
 
 LRESULT WindowEmperor::_messageHandler(HWND window, UINT const message, WPARAM const wParam, LPARAM const lParam) noexcept
 {
-    // use C++11 magic statics to make sure we only do this once.
-    // This won't change over the lifetime of the application
-    static const UINT WM_TASKBARCREATED = []() { return RegisterWindowMessageW(L"TaskbarCreated"); }();
-
     try
     {
         switch (message)
@@ -943,6 +942,7 @@ LRESULT WindowEmperor::_messageHandler(HWND window, UINT const message, WPARAM c
             // message at runtime.
             if (message == WM_TASKBARCREATED)
             {
+                _notificationIconShown = false;
                 _checkWindowsForNotificationIcon();
                 return 0;
             }

src/cascadia/WindowsTerminal/WindowEmperor.h

@@ -67,6 +67,7 @@ class WindowEmperor
     std::vector<std::shared_ptr<::AppHost>> _windows;
     std::vector<winrt::Microsoft::Terminal::Settings::Model::GlobalSummonArgs> _hotkeys;
     NOTIFYICONDATA _notificationIcon{};
+    UINT WM_TASKBARCREATED = 0;
     HMENU _currentWindowMenu = nullptr;
     bool _notificationIconShown = false;
     bool _forcePersistence = false;