Hide the window from DWM until we're finished with initialization (#1…

…2979)

When we start up, our window is initially just a frame with a transparent content area. We're gonna do all this startup init on the UI thread, so the UI won't actually paint till it's all done. This results in a few frames where the frame is visible, before the page paints for the first time, before any tabs appears, etc. 

To mitigate this, we're gonna wait for the UI thread to finish everything it's gotta do for the initial init, and _then_ fire our Initialized event. By waiting for everything else to finish (`CoreDispatcherPriority::Low`), we let all the tabs and panes actually get created. In the window layer, we're gonna ~cloak~ just not show the window till this event is fired, so we don't actually see this frame until we're actually all ready to go. **This will result in the window seemingly not loading as fast**, but it will actually take exactly the same amount of time before it's usable. 

I also experimented with drawing a solid BG color before the initialization is finished. However, there are still a few frames after the frame is displayed before the XAML content first draws, so that didn't actually resolve any issues.

* [x] Closes #11561
* [x] Tested manually
* [x] I work here.
* [x] Accidentally also closes #9053. By switching the initial call from `ShowWindow(SW_SHOW)` to `ShowWindow(SW_SHOWDEFAULT)`, we actually obey the startup info now.

.github/actions/spelling/allow/apis.txt

@@ -30,6 +30,7 @@ DERR
 dlldata
 DONTADDTORECENT
 DWORDLONG
+DWMWA
 endfor
 enumset
 environstrings
@@ -154,6 +155,7 @@ serializer
 SETVERSION
 SHELLEXECUTEINFOW
 shobjidl
+SHOWDEFAULT
 SHOWHIDE
 SHOWMINIMIZED
 SHOWTIP

src/cascadia/TerminalApp/AppLogic.h

@@ -199,6 +199,7 @@ namespace winrt::TerminalApp::implementation
         FORWARDED_TYPED_EVENT(FullscreenChanged, winrt::Windows::Foundation::IInspectable, winrt::Windows::Foundation::IInspectable, _root, FullscreenChanged);
         FORWARDED_TYPED_EVENT(ChangeMaximizeRequested, winrt::Windows::Foundation::IInspectable, winrt::Windows::Foundation::IInspectable, _root, ChangeMaximizeRequested);
         FORWARDED_TYPED_EVENT(AlwaysOnTopChanged, winrt::Windows::Foundation::IInspectable, winrt::Windows::Foundation::IInspectable, _root, AlwaysOnTopChanged);
+        FORWARDED_TYPED_EVENT(Initialized, winrt::Windows::Foundation::IInspectable, winrt::Windows::Foundation::IInspectable, _root, Initialized);
         FORWARDED_TYPED_EVENT(RaiseVisualBell, winrt::Windows::Foundation::IInspectable, winrt::Windows::Foundation::IInspectable, _root, RaiseVisualBell);
         FORWARDED_TYPED_EVENT(SetTaskbarProgress, winrt::Windows::Foundation::IInspectable, winrt::Windows::Foundation::IInspectable, _root, SetTaskbarProgress);
         FORWARDED_TYPED_EVENT(IdentifyWindowsRequested, Windows::Foundation::IInspectable, Windows::Foundation::IInspectable, _root, IdentifyWindowsRequested);

src/cascadia/TerminalApp/AppLogic.idl

@@ -122,6 +122,7 @@ namespace TerminalApp
         event Windows.Foundation.TypedEventHandler<Object, Object> FullscreenChanged;
         event Windows.Foundation.TypedEventHandler<Object, Object> ChangeMaximizeRequested;
         event Windows.Foundation.TypedEventHandler<Object, Object> AlwaysOnTopChanged;
+        event Windows.Foundation.TypedEventHandler<Object, Object> Initialized;
         event Windows.Foundation.TypedEventHandler<Object, Object> RaiseVisualBell;
         event Windows.Foundation.TypedEventHandler<Object, Object> SetTaskbarProgress;
         event Windows.Foundation.TypedEventHandler<Object, Object> IdentifyWindowsRequested;

src/cascadia/TerminalApp/TerminalPage.cpp

@@ -659,7 +659,7 @@ namespace winrt::TerminalApp::implementation
     // - <none>
     // Return Value:
     // - <none>
-    void TerminalPage::_CompleteInitialization()
+    winrt::fire_and_forget TerminalPage::_CompleteInitialization()
     {
         _startupState = StartupState::Initialized;
 
@@ -679,10 +679,55 @@ namespace winrt::TerminalApp::implementation
         if (_tabs.Size() == 0 && !(_shouldStartInboundListener || _isEmbeddingInboundListener))
         {
             _LastTabClosedHandlers(*this, nullptr);
+            co_return;
         }
         else
         {
-            _InitializedHandlers(*this, nullptr);
+            // GH#11561: When we start up, our window is initially just a frame
+            // with a transparent content area. We're gonna do all this startup
+            // init on the UI thread, so the UI won't actually paint till it's
+            // all done. This results in a few frames where the frame is
+            // visible, before the page paints for the first time, before any
+            // tabs appears, etc.
+            //
+            // To mitigate this, we're gonna wait for the UI thread to finish
+            // everything it's gotta do for the initial init, and _then_ fire
+            // our Initialized event. By waiting for everything else to finish
+            // (CoreDispatcherPriority::Low), we let all the tabs and panes
+            // actually get created. In the window layer, we're gonna cloak the
+            // window till this event is fired, so we don't actually see this
+            // frame until we're actually all ready to go.
+            //
+            // This will result in the window seemingly not loading as fast, but
+            // it will actually take exactly the same amount of time before it's
+            // usable.
+            //
+            // We also experimented with drawing a solid BG color before the
+            // initialization is finished. However, there are still a few frames
+            // after the frame is displayed before the XAML content first draws,
+            // so that didn't actually resolve any issues.
+
+            auto weak{ get_weak() };
+
+            // Switch to the BG thread -
+            co_await winrt::resume_background();
+
+            if (auto self{ weak.get() })
+            {
+                // Then enqueue the rest of this function for after the UI thread settles.
+                co_await wil::resume_foreground(self->Dispatcher(), CoreDispatcherPriority::Low);
+            }
+            else
+            {
+                // We don't exist anymore? Well, we probably don't need to fire
+                // off an Initialized event then...
+                co_return;
+            }
+
+            if (auto self{ weak.get() })
+            {
+                self->_InitializedHandlers(*self, nullptr);
+            }
         }
     }
 

src/cascadia/TerminalApp/TerminalPage.h

@@ -147,7 +147,7 @@ namespace winrt::TerminalApp::implementation
         TYPED_EVENT(AlwaysOnTopChanged, IInspectable, IInspectable);
         TYPED_EVENT(RaiseVisualBell, IInspectable, IInspectable);
         TYPED_EVENT(SetTaskbarProgress, IInspectable, IInspectable);
-        TYPED_EVENT(Initialized, IInspectable, winrt::Windows::UI::Xaml::RoutedEventArgs);
+        TYPED_EVENT(Initialized, IInspectable, IInspectable);
         TYPED_EVENT(IdentifyWindowsRequested, IInspectable, IInspectable);
         TYPED_EVENT(RenameWindowRequested, Windows::Foundation::IInspectable, winrt::TerminalApp::RenameWindowRequestedArgs);
         TYPED_EVENT(IsQuakeWindowChanged, IInspectable, IInspectable);
@@ -390,7 +390,7 @@ namespace winrt::TerminalApp::implementation
 
         void _StartInboundListener();
 
-        void _CompleteInitialization();
+        winrt::fire_and_forget _CompleteInitialization();
 
         void _FocusActiveControl(IInspectable sender, IInspectable eventArgs);
 

src/cascadia/TerminalApp/TerminalPage.idl

@@ -51,7 +51,7 @@ namespace TerminalApp
         event Windows.Foundation.TypedEventHandler<Object, Object> FocusModeChanged;
         event Windows.Foundation.TypedEventHandler<Object, Object> FullscreenChanged;
         event Windows.Foundation.TypedEventHandler<Object, Object> AlwaysOnTopChanged;
-        event Windows.Foundation.TypedEventHandler<Object, Windows.UI.Xaml.RoutedEventArgs> Initialized;
+        event Windows.Foundation.TypedEventHandler<Object, Object> Initialized;
         event Windows.Foundation.TypedEventHandler<Object, Object> SetTaskbarProgress;
         event Windows.Foundation.TypedEventHandler<Object, Object> IdentifyWindowsRequested;
         event Windows.Foundation.TypedEventHandler<Object, RenameWindowRequestedArgs> RenameWindowRequested;

src/cascadia/WindowsTerminal/AppHost.cpp

@@ -73,8 +73,7 @@ AppHost::AppHost() noexcept :
     auto pfn = std::bind(&AppHost::_HandleCreateWindow,
                          this,
                          std::placeholders::_1,
-                         std::placeholders::_2,
-                         std::placeholders::_3);
+                         std::placeholders::_2);
     _window->SetCreateCallback(pfn);
 
     _window->SetSnapDimensionCallback(std::bind(&winrt::TerminalApp::AppLogic::CalcSnappedDimension,
@@ -379,6 +378,7 @@ void AppHost::Initialize()
     _revokers.FullscreenChanged = _logic.FullscreenChanged(winrt::auto_revoke, { this, &AppHost::_FullscreenChanged });
     _revokers.FocusModeChanged = _logic.FocusModeChanged(winrt::auto_revoke, { this, &AppHost::_FocusModeChanged });
     _revokers.AlwaysOnTopChanged = _logic.AlwaysOnTopChanged(winrt::auto_revoke, { this, &AppHost::_AlwaysOnTopChanged });
+    _revokers.Initialized = _logic.Initialized(winrt::auto_revoke, { this, &AppHost::_AppInitializedHandler });
     _revokers.RaiseVisualBell = _logic.RaiseVisualBell(winrt::auto_revoke, { this, &AppHost::_RaiseVisualBell });
     _revokers.SystemMenuChangeRequested = _logic.SystemMenuChangeRequested(winrt::auto_revoke, { this, &AppHost::_SystemMenuChangeRequested });
     _revokers.ChangeMaximizeRequested = _logic.ChangeMaximizeRequested(winrt::auto_revoke, { this, &AppHost::_ChangeMaximizeRequested });
@@ -520,12 +520,31 @@ LaunchPosition AppHost::_GetWindowLaunchPosition()
     return pos;
 }
 
+// Method Description:
+// - Callback for when the window is first being created (during WM_CREATE).
+//   Stash the proposed size for later. We'll need that once we're totally
+//   initialized, so that we can show the window in the right position *when we
+//   want to show it*. If we did the _initialResizeAndRepositionWindow work now,
+//   it would have no effect, because the window is not yet visible.
+// Arguments:
+// - hwnd: The HWND of the window we're about to create.
+// - proposedRect: The location and size of the window that we're about to
+//   create. We'll use this rect to determine which monitor the window is about
+//   to appear on.
+void AppHost::_HandleCreateWindow(const HWND /* hwnd */, RECT proposedRect)
+{
+    // GH#11561: Hide the window until we're totally done being initialized.
+    // More commentary in TerminalPage::_CompleteInitialization
+    _proposedRect = proposedRect;
+}
+
 // Method Description:
 // - Resize the window we're about to create to the appropriate dimensions, as
-//   specified in the settings. This will be called during the handling of
-//   WM_CREATE. We'll load the settings for the app, then get the proposed size
-//   of the terminal from the app. Using that proposed size, we'll resize the
-//   window we're creating, so that it'll match the values in the settings.
+//   specified in the settings. This is called once the app has finished it's
+//   initial setup, once we have created all the tabs, panes, etc. We'll load
+//   the settings for the app, then get the proposed size of the terminal from
+//   the app. Using that proposed size, we'll resize the window we're creating,
+//   so that it'll match the values in the settings.
 // Arguments:
 // - hwnd: The HWND of the window we're about to create.
 // - proposedRect: The location and size of the window that we're about to
@@ -534,7 +553,7 @@ LaunchPosition AppHost::_GetWindowLaunchPosition()
 // - launchMode: A LaunchMode enum reference that indicates the launch mode
 // Return Value:
 // - None
-void AppHost::_HandleCreateWindow(const HWND hwnd, RECT proposedRect, LaunchMode& launchMode)
+void AppHost::_initialResizeAndRepositionWindow(const HWND hwnd, RECT proposedRect, LaunchMode& launchMode)
 {
     launchMode = _logic.GetLaunchMode();
 
@@ -1556,3 +1575,22 @@ void AppHost::_CloseRequested(const winrt::Windows::Foundation::IInspectable& /*
     const auto pos = _GetWindowLaunchPosition();
     _logic.CloseWindow(pos);
 }
+
+void AppHost::_AppInitializedHandler(const winrt::Windows::Foundation::IInspectable& /*sender*/,
+                                     const winrt::Windows::Foundation::IInspectable& /*arg*/)
+{
+    // GH#11561: We're totally done being initialized. Resize the window to
+    // match the initial settings, and then call ShowWindow to finally make us
+    // visible.
+
+    LaunchMode launchMode{};
+    _initialResizeAndRepositionWindow(_window->GetHandle(), _proposedRect, launchMode);
+
+    auto nCmdShow = SW_SHOWDEFAULT;
+    if (WI_IsFlagSet(launchMode, LaunchMode::MaximizedMode))
+    {
+        nCmdShow = SW_MAXIMIZE;
+    }
+
+    ShowWindow(_window->GetHandle(), nCmdShow);
+}

src/cascadia/WindowsTerminal/AppHost.h

@@ -31,6 +31,7 @@ class AppHost
 
     bool _shouldCreateWindow{ false };
     bool _useNonClientArea{ false };
+    RECT _proposedRect{};
 
     std::optional<til::throttled_func_trailing<>> _getWindowLayoutThrottler;
     winrt::Windows::Foundation::IAsyncAction _SaveWindowLayouts();
@@ -39,7 +40,7 @@ class AppHost
     void _HandleCommandlineArgs();
     winrt::Microsoft::Terminal::Settings::Model::LaunchPosition _GetWindowLaunchPosition();
 
-    void _HandleCreateWindow(const HWND hwnd, RECT proposedRect, winrt::Microsoft::Terminal::Settings::Model::LaunchMode& launchMode);
+    void _HandleCreateWindow(const HWND hwnd, RECT proposedRect);
     void _UpdateTitleBarContent(const winrt::Windows::Foundation::IInspectable& sender,
                                 const winrt::Windows::UI::Xaml::UIElement& arg);
     void _UpdateTheme(const winrt::Windows::Foundation::IInspectable&,
@@ -52,6 +53,9 @@ class AppHost
                                   const winrt::Windows::Foundation::IInspectable& arg);
     void _AlwaysOnTopChanged(const winrt::Windows::Foundation::IInspectable& sender,
                              const winrt::Windows::Foundation::IInspectable& arg);
+    void _AppInitializedHandler(const winrt::Windows::Foundation::IInspectable& sender,
+                                const winrt::Windows::Foundation::IInspectable& arg);
+
     void _RaiseVisualBell(const winrt::Windows::Foundation::IInspectable& sender,
                           const winrt::Windows::Foundation::IInspectable& arg);
     void _WindowMouseWheeled(const til::point coord, const int32_t delta);
@@ -121,6 +125,9 @@ class AppHost
                                         const winrt::Windows::Foundation::IInspectable& args);
     void _HideNotificationIconRequested(const winrt::Windows::Foundation::IInspectable& sender,
                                         const winrt::Windows::Foundation::IInspectable& args);
+
+    void _initialResizeAndRepositionWindow(const HWND hwnd, RECT proposedRect, winrt::Microsoft::Terminal::Settings::Model::LaunchMode& launchMode);
+
     std::unique_ptr<NotificationIcon> _notificationIcon;
     winrt::event_token _ReAddNotificationIconToken;
     winrt::event_token _NotificationIconPressedToken;
@@ -147,6 +154,7 @@ class AppHost
         winrt::TerminalApp::AppLogic::FullscreenChanged_revoker FullscreenChanged;
         winrt::TerminalApp::AppLogic::FocusModeChanged_revoker FocusModeChanged;
         winrt::TerminalApp::AppLogic::AlwaysOnTopChanged_revoker AlwaysOnTopChanged;
+        winrt::TerminalApp::AppLogic::Initialized_revoker Initialized;
         winrt::TerminalApp::AppLogic::RaiseVisualBell_revoker RaiseVisualBell;
         winrt::TerminalApp::AppLogic::SystemMenuChangeRequested_revoker SystemMenuChangeRequested;
         winrt::TerminalApp::AppLogic::ChangeMaximizeRequested_revoker ChangeMaximizeRequested;

src/cascadia/WindowsTerminal/IslandWindow.cpp

@@ -112,7 +112,7 @@ void IslandWindow::Close()
 //        window.
 // Return Value:
 // - <none>
-void IslandWindow::SetCreateCallback(std::function<void(const HWND, const RECT, LaunchMode& launchMode)> pfn) noexcept
+void IslandWindow::SetCreateCallback(std::function<void(const HWND, const RECT)> pfn) noexcept
 {
     _pfnCreateCallback = pfn;
 }
@@ -154,19 +154,13 @@ void IslandWindow::_HandleCreateWindow(const WPARAM, const LPARAM lParam) noexce
     rc.right = rc.left + pcs->cx;
     rc.bottom = rc.top + pcs->cy;
 
-    auto launchMode = LaunchMode::DefaultMode;
     if (_pfnCreateCallback)
     {
-        _pfnCreateCallback(_window.get(), rc, launchMode);
+        _pfnCreateCallback(_window.get(), rc);
     }
 
-    auto nCmdShow = SW_SHOW;
-    if (WI_IsFlagSet(launchMode, LaunchMode::MaximizedMode))
-    {
-        nCmdShow = SW_MAXIMIZE;
-    }
-
-    ShowWindow(_window.get(), nCmdShow);
+    // GH#11561: DO NOT call ShowWindow here. The AppHost will call ShowWindow
+    // once the app has completed its initialization.
 
     UpdateWindow(_window.get());
 

src/cascadia/WindowsTerminal/IslandWindow.h

@@ -37,7 +37,7 @@ class IslandWindow :
 
     virtual void Initialize();
 
-    void SetCreateCallback(std::function<void(const HWND, const RECT, winrt::Microsoft::Terminal::Settings::Model::LaunchMode& launchMode)> pfn) noexcept;
+    void SetCreateCallback(std::function<void(const HWND, const RECT)> pfn) noexcept;
     void SetSnapDimensionCallback(std::function<float(bool widthOrHeight, float dimension)> pfn) noexcept;
 
     void FocusModeChanged(const bool focusMode);
@@ -94,7 +94,7 @@ class IslandWindow :
     winrt::Windows::UI::Xaml::Controls::Grid _rootGrid;
     wil::com_ptr<ITaskbarList3> _taskbar;
 
-    std::function<void(const HWND, const RECT, winrt::Microsoft::Terminal::Settings::Model::LaunchMode& launchMode)> _pfnCreateCallback;
+    std::function<void(const HWND, const RECT)> _pfnCreateCallback;
     std::function<float(bool, float)> _pfnSnapDimensionCallback;
 
     void _HandleCreateWindow(const WPARAM wParam, const LPARAM lParam) noexcept;