Fix multiple regressions since #18215 (#18345)

Fixes
* Cursor vanishing, because
  ```cpp
  CoreWindow::GetForCurrentThread().PointerCursor()
  ```
  returned a non-null, but still invisible cursor.
* Alt/F7 not dispatching to newly created windows, because the
  `WM_ACTIVATE` message now arrives before the `AppHost` is initialized.
  This caused the messages to be delivered to old windows.
* Windows Terminal blocking expedited shutdown,
  because we return `FALSE` on non-`ENDSESSION_CLOSEAPP` messages.

Closes #18331
Closes #18335

## Validation Steps Performed
* Cursor still doesn't really vanish for me in the first place ✅
* Alt/F7 work in new windows without triggering old ones ✅

src/cascadia/TerminalControl/TermControl.cpp

@@ -57,7 +57,7 @@ DEFINE_ENUM_FLAG_OPERATORS(winrt::Microsoft::Terminal::Control::MouseButtonState
 //   the current foreground window, but still on top of another Terminal window in the background.
 static void hideCursorUntilMoved()
 {
-    static CoreCursor previousCursor{ nullptr };
+    static bool cursorIsHidden;
     static const auto shouldVanish = []() {
         BOOL shouldVanish = TRUE;
         SystemParametersInfoW(SPI_GETMOUSEVANISH, 0, &shouldVanish, 0);
@@ -68,16 +68,16 @@ static void hideCursorUntilMoved()
 
         const auto window = CoreWindow::GetForCurrentThread();
         static constexpr auto releaseCapture = [](CoreWindow window, PointerEventArgs) {
-            if (previousCursor)
+            if (cursorIsHidden)
             {
                 window.ReleasePointerCapture();
             }
         };
         static constexpr auto restoreCursor = [](CoreWindow window, PointerEventArgs) {
-            if (previousCursor)
+            if (cursorIsHidden)
             {
-                window.PointerCursor(previousCursor);
-                previousCursor = nullptr;
+                cursorIsHidden = false;
+                window.PointerCursor(CoreCursor{ CoreCursorType::Arrow, 0 });
             }
         };
 
@@ -90,20 +90,14 @@ static void hideCursorUntilMoved()
         return true;
     }();
 
-    if (shouldVanish && !previousCursor)
+    if (shouldVanish && !cursorIsHidden)
     {
         try
         {
             const auto window = CoreWindow::GetForCurrentThread();
-
-            previousCursor = window.PointerCursor();
-            if (!previousCursor)
-            {
-                return;
-            }
-
             window.PointerCursor(nullptr);
             window.SetPointerCapture();
+            cursorIsHidden = true;
         }
         catch (...)
         {

src/cascadia/WindowsTerminal/AppHost.cpp

@@ -815,7 +815,7 @@ void AppHost::_WindowActivated(bool activated)
 {
     _windowLogic.WindowActivated(activated);
 
-    if (activated && _isWindowInitialized != WindowInitializedState::NotInitialized)
+    if (activated)
     {
         QueryPerformanceCounter(&_lastActivatedTime);
         _virtualDesktopId = {};

src/cascadia/WindowsTerminal/WindowEmperor.cpp

@@ -413,13 +413,8 @@ void WindowEmperor::HandleCommandlineArgs(int nCmdShow)
                 // It almost seems like there's a pattern here...
                 (msg.wParam == VK_SPACE && msg.message == WM_SYSKEYDOWN))
             {
-                if (const auto w = _mostRecentWindow())
-                {
-                    const auto vkey = gsl::narrow_cast<uint32_t>(msg.wParam);
-                    const auto scanCode = gsl::narrow_cast<uint8_t>(msg.lParam >> 16);
-                    w->OnDirectKeyEvent(vkey, scanCode, keyDown);
-                    continue;
-                }
+                _dispatchSpecialKey(msg);
+                continue;
             }
         }
 
@@ -442,6 +437,40 @@ void WindowEmperor::HandleCommandlineArgs(int nCmdShow)
     __assume(false);
 }
 
+void WindowEmperor::_dispatchSpecialKey(MSG& msg) const
+{
+    const auto hwnd = msg.hwnd;
+    AppHost* window = nullptr;
+
+    // Just in case someone has targed a specific HWND,
+    // we'll try to dispatch it to the corresponding class.
+    // Usually this will not find anything because under WinUI the hidden CoreInput
+    // window is responsible for all input handling (for whatever reason).
+    for (const auto& h : _windows)
+    {
+        const auto w = h->GetWindow();
+        if (w && w->GetHandle() == hwnd)
+        {
+            window = h.get();
+            break;
+        }
+    }
+
+    if (!window)
+    {
+        window = _mostRecentWindow();
+        if (!window)
+        {
+            return;
+        }
+    }
+
+    const auto vkey = gsl::narrow_cast<uint32_t>(msg.wParam);
+    const auto scanCode = gsl::narrow_cast<uint8_t>(msg.lParam >> 16);
+    const bool keyDown = msg.message & 1;
+    window->OnDirectKeyEvent(vkey, scanCode, keyDown);
+}
+
 void WindowEmperor::_dispatchCommandline(winrt::TerminalApp::CommandlineArgs args)
 {
     const auto exitCode = args.ExitCode();
@@ -826,14 +855,10 @@ LRESULT WindowEmperor::_messageHandler(HWND window, UINT const message, WPARAM c
         case WM_QUERYENDSESSION:
             // For WM_QUERYENDSESSION and WM_ENDSESSION, refer to:
             // https://docs.microsoft.com/en-us/windows/win32/rstmgr/guidelines-for-applications
-            if (lParam == ENDSESSION_CLOSEAPP)
-            {
-                // ENDSESSION_CLOSEAPP: The application is using a file that must be replaced,
-                // the system is being serviced, or system resources are exhausted.
-                RegisterApplicationRestart(nullptr, RESTART_NO_CRASH | RESTART_NO_HANG);
-                return TRUE;
-            }
-            return FALSE;
+            // ENDSESSION_CLOSEAPP: The application is using a file that must be replaced,
+            // the system is being serviced, or system resources are exhausted.
+            RegisterApplicationRestart(nullptr, RESTART_NO_CRASH | RESTART_NO_HANG);
+            return TRUE;
         case WM_ENDSESSION:
             _forcePersistence = true;
             PostQuitMessage(0);

src/cascadia/WindowsTerminal/WindowEmperor.h

@@ -50,6 +50,7 @@ class WindowEmperor
     AppHost* _mostRecentWindow() const noexcept;
     bool _summonWindow(const SummonWindowSelectionArgs& args) const;
     void _summonAllWindows() const;
+    void _dispatchSpecialKey(MSG& msg) const;
     void _dispatchCommandline(winrt::TerminalApp::CommandlineArgs args);
     safe_void_coroutine _dispatchCommandlineCurrentDesktop(winrt::TerminalApp::CommandlineArgs args);
     LRESULT _messageHandler(HWND window, UINT message, WPARAM wParam, LPARAM lParam) noexcept;