Avoid focus loops in ConPTY

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

@@ -96,6 +96,7 @@ IGraphics
 IImage
 IInheritable
 IMap
+imm
 IMonarch
 IObject
 iosfwd

src/cascadia/TerminalControl/ControlCore.cpp

@@ -201,6 +201,17 @@ namespace winrt::Microsoft::Terminal::Control::implementation
                 }
             });
 
+        // If you rapidly show/hide Windows Terminal, something about GotFocus()/LostFocus() gets broken.
+        // We'll then receive easily 10+ such calls from WinUI the next time the application is shown.
+        shared->focusChanged = std::make_unique<til::debounced_func_trailing<bool>>(
+            std::chrono::milliseconds{ 25 },
+            [weakThis = get_weak()](const bool focused) {
+                if (const auto core{ weakThis.get() })
+                {
+                    core->_focusChanged(focused);
+                }
+            });
+
         // Scrollbar updates are also expensive (XAML), so we'll throttle them as well.
         shared->updateScrollBar = std::make_shared<ThrottledFuncTrailing<Control::ScrollPositionChangedArgs>>(
             _dispatcher,
@@ -2480,13 +2491,21 @@ namespace winrt::Microsoft::Terminal::Control::implementation
     // - This is related to work done for GH#2988.
     void ControlCore::GotFocus()
     {
-        _focusChanged(true);
+        const auto shared = _shared.lock_shared();
+        if (shared->focusChanged)
+        {
+            (*shared->focusChanged)(true);
+        }
     }
 
     // See GotFocus.
     void ControlCore::LostFocus()
     {
-        _focusChanged(false);
+        const auto shared = _shared.lock_shared();
+        if (shared->focusChanged)
+        {
+            (*shared->focusChanged)(false);
+        }
     }
 
     void ControlCore::_focusChanged(bool focused)

src/cascadia/TerminalControl/ControlCore.h

@@ -307,6 +307,7 @@ namespace winrt::Microsoft::Terminal::Control::implementation
         struct SharedState
         {
             std::unique_ptr<til::debounced_func_trailing<>> outputIdle;
+            std::unique_ptr<til::debounced_func_trailing<bool>> focusChanged;
             std::shared_ptr<ThrottledFuncTrailing<Control::ScrollPositionChangedArgs>> updateScrollBar;
         };
 

src/host/PtySignalInputThread.cpp

@@ -74,8 +74,6 @@ void PtySignalInputThread::ConnectConsole() noexcept
     {
         _DoShowHide(*_initialShowHide);
     }
-
-    // We should have successfully used the _earlyReparent message in CreatePseudoWindow.
 }
 
 // Method Description:
@@ -87,8 +85,7 @@ void PtySignalInputThread::ConnectConsole() noexcept
 // - Refer to GH#13066 for details.
 void PtySignalInputThread::CreatePseudoWindow()
 {
-    HWND owner = _earlyReparent.has_value() ? reinterpret_cast<HWND>((*_earlyReparent).handle) : HWND_DESKTOP;
-    ServiceLocator::LocatePseudoWindow(owner);
+    ServiceLocator::LocatePseudoWindow();
 }
 
 // Method Description:
@@ -220,7 +217,7 @@ void PtySignalInputThread::_DoShowHide(const ShowHideData& data)
         return;
     }
 
-    _api.ShowWindow(data.show);
+    ServiceLocator::SetPseudoWindowVisibility(data.show);
 }
 
 // Method Description:
@@ -237,44 +234,7 @@ void PtySignalInputThread::_DoSetWindowParent(const SetParentData& data)
     LockConsole();
     auto Unlock = wil::scope_exit([&] { UnlockConsole(); });
 
-    // If the client app hasn't yet connected, stash the new owner.
-    // We'll later (PtySignalInputThread::ConnectConsole) use the value
-    // to set up the owner of the conpty window.
-    if (!_consoleConnected)
-    {
-        _earlyReparent = data;
-        return;
-    }
-
-    const auto owner{ reinterpret_cast<HWND>(data.handle) };
-    // This will initialize s_interactivityFactory for us. It will also
-    // conveniently return 0 when we're on OneCore.
-    //
-    // If the window hasn't been created yet, by some other call to
-    // LocatePseudoWindow, then this will also initialize the owner of the
-    // window.
-    if (const auto pseudoHwnd{ ServiceLocator::LocatePseudoWindow(owner) })
-    {
-        // SetWindowLongPtrW may call back into the message handler and wait for it to finish,
-        // similar to SendMessageW(). If the conhost message handler is already processing and
-        // waiting to acquire the console lock, which we're currently holding, we'd deadlock.
-        // --> Release the lock now.
-        Unlock.reset();
-
-        // DO NOT USE SetParent HERE!
-        //
-        // Calling SetParent on a window that is WS_VISIBLE will cause the OS to
-        // hide the window, make it a _child_ window, then call SW_SHOW on the
-        // window to re-show it. SW_SHOW, however, will cause the OS to also set
-        // that window as the _foreground_ window, which would result in the
-        // pty's hwnd stealing the foreground away from the owning terminal
-        // window. That's bad.
-        //
-        // SetWindowLongPtr seems to do the job of changing who the window owner
-        // is, without all the other side effects of reparenting the window.
-        // See #13066
-        ::SetWindowLongPtrW(pseudoHwnd, GWLP_HWNDPARENT, reinterpret_cast<LONG_PTR>(owner));
-    }
+    ServiceLocator::SetPseudoWindowOwner(reinterpret_cast<HWND>(data.handle));
 }
 
 // Method Description:

src/host/PtySignalInputThread.hpp

@@ -75,8 +75,5 @@ namespace Microsoft::Console
         std::optional<ResizeWindowData> _earlyResize;
         std::optional<ShowHideData> _initialShowHide;
         ConhostInternalGetSet _api;
-
-    public:
-        std::optional<SetParentData> _earlyReparent;
     };
 }

src/host/exe/Host.EXE.vcxproj

@@ -86,7 +86,7 @@
     </ClCompile>
     <Link>
       <AllowIsolation>true</AllowIsolation>
-      <AdditionalDependencies>WinMM.Lib;%(AdditionalDependencies)</AdditionalDependencies>
+      <AdditionalDependencies>winmm.lib;imm32.lib;%(AdditionalDependencies)</AdditionalDependencies>
     </Link>
   </ItemDefinitionGroup>
   <!-- Careful reordering these. Some default props (contained in these files) are order sensitive. -->

src/host/outputStream.cpp

@@ -208,15 +208,22 @@ CursorType ConhostInternalGetSet::GetUserDefaultCursorStyle() const
 // - <none>
 void ConhostInternalGetSet::ShowWindow(bool showOrHide)
 {
-    auto& gci = ServiceLocator::LocateGlobals().getConsoleInformation();
-    const auto hwnd = gci.IsInVtIoMode() ? ServiceLocator::LocatePseudoWindow() : ServiceLocator::LocateConsoleWindow()->GetWindowHandle();
+    // ConPTY is supposed to be "transparent" to the VT application. Any VT it processes is given to the terminal.
+    // As such, it must not react to this "CSI 1 t" or "CSI 2 t" sequence. That's the job of the terminal.
+    // If the terminal encounters such a sequence, it can show/hide itself and let ConPTY know via its signal API.
+    const auto window = ServiceLocator::LocateConsoleWindow();
+    if (!window)
+    {
+        return;
+    }
 
     // GH#13301 - When we send this ShowWindow message, if we send it to the
     // conhost HWND, it's going to need to get processed by the window message
     // thread before returning.
     // However, ShowWindowAsync doesn't have this problem. It'll post the
     // message to the window thread, then immediately return, so we don't have
     // to worry about deadlocking.
+    const auto hwnd = window->GetWindowHandle();
     ::ShowWindowAsync(hwnd, showOrHide ? SW_SHOWNOACTIVATE : SW_MINIMIZE);
 }
 

src/interactivity/base/InteractivityFactory.cpp

@@ -294,7 +294,7 @@ using namespace Microsoft::Console::Interactivity;
 // - owner: the HWND that should be the initial owner of the pseudo window.
 // Return Value:
 // - STATUS_SUCCESS on success, otherwise an appropriate error.
-[[nodiscard]] NTSTATUS InteractivityFactory::CreatePseudoWindow(HWND& hwnd, const HWND owner)
+[[nodiscard]] NTSTATUS InteractivityFactory::CreatePseudoWindow(HWND& hwnd)
 {
     hwnd = nullptr;
     ApiLevel level;
@@ -310,6 +310,11 @@ using namespace Microsoft::Console::Interactivity;
             {
             case ApiLevel::Win32:
             {
+                // We don't need an "Default IME" window for ConPTY. That's the terminal's job.
+                // -1, aka DWORD_MAX, tells the function to disable it for the entire process.
+                // Must be called before creating any window.
+                ImmDisableIME(DWORD_MAX);
+
                 pseudoClass.cbSize = sizeof(WNDCLASSEXW);
                 pseudoClass.lpszClassName = PSEUDO_WINDOW_CLASS;
                 pseudoClass.lpfnWndProc = s_PseudoWindowProc;
@@ -330,19 +335,15 @@ using namespace Microsoft::Console::Interactivity;
                 // will return the console handle again, not the owning
                 // terminal's handle. It's not entirely clear why, but WS_POPUP
                 // is absolutely vital for this to work correctly.
-                const auto windowStyle = WS_OVERLAPPEDWINDOW | WS_POPUP;
-                const auto exStyles = WS_EX_TOOLWINDOW | WS_EX_TRANSPARENT | WS_EX_LAYERED | WS_EX_NOACTIVATE;
-
-                // Attempt to create window.
-                hwnd = CreateWindowExW(exStyles,
+                hwnd = CreateWindowExW(WS_EX_TOOLWINDOW | WS_EX_NOACTIVATE,
                                        reinterpret_cast<LPCWSTR>(windowClassAtom),
                                        nullptr,
-                                       windowStyle,
+                                       WS_POPUP,
                                        0,
                                        0,
                                        0,
                                        0,
-                                       owner,
+                                       _owner.load(std::memory_order_relaxed),
                                        nullptr,
                                        nullptr,
                                        this);
@@ -375,6 +376,38 @@ using namespace Microsoft::Console::Interactivity;
     return status;
 }
 
+void InteractivityFactory::SetOwner(HWND owner) noexcept
+{
+    _owner.store(owner, std::memory_order_relaxed);
+
+    if (_pseudoConsoleWindowHwnd)
+    {
+        // DO NOT USE SetParent HERE!
+        //
+        // Calling SetParent on a window that is WS_VISIBLE will cause the OS to
+        // hide the window, make it a _child_ window, then call SW_SHOW on the
+        // window to re-show it. SW_SHOW, however, will cause the OS to also set
+        // that window as the _foreground_ window, which would result in the
+        // pty's hwnd stealing the foreground away from the owning terminal
+        // window. That's bad.
+        //
+        // SetWindowLongPtr seems to do the job of changing who the window owner
+        // is, without all the other side effects of reparenting the window.
+        // See #13066
+        ::SetWindowLongPtrW(_pseudoConsoleWindowHwnd, GWLP_HWNDPARENT, reinterpret_cast<LONG_PTR>(owner));
+    }
+}
+
+void InteractivityFactory::SetVisibility(const bool isVisible) noexcept
+{
+    if (_pseudoConsoleWindowHwnd && IsIconic(_pseudoConsoleWindowHwnd) != static_cast<BOOL>(isVisible))
+    {
+        _suppressVisibilityChange.store(true, std::memory_order_relaxed);
+        ShowWindow(_pseudoConsoleWindowHwnd, isVisible ? SW_SHOWNOACTIVATE : SW_MINIMIZE);
+        _suppressVisibilityChange.store(false, std::memory_order_relaxed);
+    }
+}
+
 // Method Description:
 // - Static window procedure for pseudo console windows
 // - Processes set-up on create to stow the "this" pointer to specific instantiations and routes
@@ -446,7 +479,7 @@ using namespace Microsoft::Console::Interactivity;
         {
             _WritePseudoWindowCallback(false);
         }
-        break;
+        return 0;
     }
     // case WM_WINDOWPOSCHANGING:
     //     As long as user32 didn't eat the `ShowWindow` call because the window state requested
@@ -479,12 +512,12 @@ using namespace Microsoft::Console::Interactivity;
     }
     case WM_ACTIVATE:
     {
-        if (const auto ownerHwnd{ ::GetAncestor(hWnd, GA_ROOTOWNER) })
+        if (const auto ownerHwnd = _owner.load(std::memory_order_relaxed))
         {
             SetFocus(ownerHwnd);
             return 0;
         }
-        break;
+        return 0;
     }
     }
     // If we get this far, call the default window proc
@@ -501,6 +534,11 @@ using namespace Microsoft::Console::Interactivity;
 // - <none>
 void InteractivityFactory::_WritePseudoWindowCallback(bool showOrHide)
 {
+    if (_suppressVisibilityChange.load(std::memory_order_relaxed))
+    {
+        return;
+    }
+
     // IMPORTANT!
     //
     // A hosting terminal window should only "restore" itself in response to

src/interactivity/base/InteractivityFactory.hpp

@@ -27,7 +27,10 @@ namespace Microsoft::Console::Interactivity
         [[nodiscard]] NTSTATUS CreateAccessibilityNotifier(_Inout_ std::unique_ptr<IAccessibilityNotifier>& notifier);
         [[nodiscard]] NTSTATUS CreateSystemConfigurationProvider(_Inout_ std::unique_ptr<ISystemConfigurationProvider>& provider);
 
-        [[nodiscard]] NTSTATUS CreatePseudoWindow(HWND& hwnd, const HWND owner);
+        [[nodiscard]] NTSTATUS CreatePseudoWindow(HWND& hwnd);
+
+        void SetOwner(HWND owner) noexcept;
+        void SetVisibility(const bool isVisible) noexcept;
 
         // Wndproc
         [[nodiscard]] static LRESULT CALLBACK s_PseudoWindowProc(_In_ HWND hwnd,
@@ -43,6 +46,8 @@ namespace Microsoft::Console::Interactivity
         void _WritePseudoWindowCallback(bool showOrHide);
 
         HWND _pseudoConsoleWindowHwnd{ nullptr };
+        std::atomic<HWND> _owner{ HWND_DESKTOP };
+        std::atomic<bool> _suppressVisibilityChange{ false };
         WRL::ComPtr<PseudoConsoleWindowAccessibilityProvider> _pPseudoConsoleUiaProvider{ nullptr };
     };
 }

src/interactivity/base/ServiceLocator.cpp

@@ -322,7 +322,7 @@ Globals& ServiceLocator::LocateGlobals()
 //   owner of the pseudo window.
 // Return Value:
 // - a reference to the pseudoconsole window.
-HWND ServiceLocator::LocatePseudoWindow(const HWND owner)
+HWND ServiceLocator::LocatePseudoWindow()
 {
     auto status = STATUS_SUCCESS;
     if (!s_pseudoWindowInitialized)
@@ -335,7 +335,7 @@ HWND ServiceLocator::LocatePseudoWindow(const HWND owner)
         if (SUCCEEDED_NTSTATUS(status))
         {
             HWND hwnd;
-            status = s_interactivityFactory->CreatePseudoWindow(hwnd, owner);
+            status = s_interactivityFactory->CreatePseudoWindow(hwnd);
             s_pseudoWindow.reset(hwnd);
         }
 
@@ -345,6 +345,38 @@ HWND ServiceLocator::LocatePseudoWindow(const HWND owner)
     return s_pseudoWindow.get();
 }
 
+void ServiceLocator::SetPseudoWindowOwner(HWND owner)
+{
+    auto status = STATUS_SUCCESS;
+    if (!s_interactivityFactory)
+    {
+        status = ServiceLocator::LoadInteractivityFactory();
+    }
+
+    if (s_interactivityFactory)
+    {
+        static_cast<InteractivityFactory*>(s_interactivityFactory.get())->SetOwner(owner);
+    }
+
+    LOG_IF_NTSTATUS_FAILED(status);
+}
+
+void ServiceLocator::SetPseudoWindowVisibility(bool showOrHide)
+{
+    auto status = STATUS_SUCCESS;
+    if (!s_interactivityFactory)
+    {
+        status = ServiceLocator::LoadInteractivityFactory();
+    }
+
+    if (s_interactivityFactory)
+    {
+        static_cast<InteractivityFactory*>(s_interactivityFactory.get())->SetVisibility(showOrHide);
+    }
+
+    LOG_IF_NTSTATUS_FAILED(status);
+}
+
 #pragma endregion
 
 #pragma region Private Methods

src/interactivity/inc/IInteractivityFactory.hpp

@@ -40,6 +40,6 @@ namespace Microsoft::Console::Interactivity
         [[nodiscard]] virtual NTSTATUS CreateAccessibilityNotifier(_Inout_ std::unique_ptr<IAccessibilityNotifier>& notifier) = 0;
         [[nodiscard]] virtual NTSTATUS CreateSystemConfigurationProvider(_Inout_ std::unique_ptr<ISystemConfigurationProvider>& provider) = 0;
 
-        [[nodiscard]] virtual NTSTATUS CreatePseudoWindow(HWND& hwnd, const HWND owner) = 0;
+        [[nodiscard]] virtual NTSTATUS CreatePseudoWindow(HWND& hwnd) = 0;
     };
 }

src/interactivity/inc/ServiceLocator.hpp

@@ -84,7 +84,9 @@ namespace Microsoft::Console::Interactivity
 
         static Globals& LocateGlobals();
 
-        static HWND LocatePseudoWindow(const HWND owner = nullptr /*HWND_DESKTOP = 0*/);
+        static HWND LocatePseudoWindow();
+        static void SetPseudoWindowOwner(HWND owner);
+        static void SetPseudoWindowVisibility(bool showOrHide);
 
         ServiceLocator(const ServiceLocator&) = delete;
         ServiceLocator& operator=(const ServiceLocator&) = delete;