Hide the window from DWM until we're finished with initialization

.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;