From e95e2bfd29b64d3144515c30fb9cf76adb75c6c3 Mon Sep 17 00:00:00 2001
From: Sine Striker <trueful@163.com>
Date: 周二, 07 5月 2024 21:44:21 +0800
Subject: [PATCH] minor tweaks

---
 src/core/contexts/win32windowcontext.cpp |  390 +++++++++++++++++++++++++++++++++++++------------------
 1 files changed, 264 insertions(+), 126 deletions(-)

diff --git a/src/core/contexts/win32windowcontext.cpp b/src/core/contexts/win32windowcontext.cpp
index 17a42c1..171a348 100644
--- a/src/core/contexts/win32windowcontext.cpp
+++ b/src/core/contexts/win32windowcontext.cpp
@@ -1,14 +1,21 @@
+// Copyright (C) 2023-2024 Stdware Collections (https://www.github.com/stdware)
+// Copyright (C) 2021-2023 wangwenx190 (Yuhang Zhao)
+// SPDX-License-Identifier: Apache-2.0
+
 #include "win32windowcontext_p.h"
 
 #include <optional>
 
+#include <QtCore/QAbstractEventDispatcher>
+#include <QtCore/QDateTime>
 #include <QtCore/QHash>
 #include <QtCore/QScopeGuard>
 #include <QtCore/QTimer>
-#include <QtCore/QDateTime>
 #include <QtGui/QGuiApplication>
 #include <QtGui/QPainter>
 #include <QtGui/QPalette>
+
+#include <QtGui/qpa/qwindowsysteminterface.h>
 
 #include <QtGui/private/qhighdpiscaling_p.h>
 #if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
@@ -94,18 +101,6 @@
         return monitorInfo;
     }
 
-    static inline void moveWindowToDesktopCenter(HWND hwnd) {
-        MONITORINFOEXW monitorInfo = getMonitorForWindow(hwnd);
-        RECT windowRect{};
-        ::GetWindowRect(hwnd, &windowRect);
-        const auto newX = monitorInfo.rcMonitor.left +
-                          (RECT_WIDTH(monitorInfo.rcMonitor) - RECT_WIDTH(windowRect)) / 2;
-        const auto newY = monitorInfo.rcMonitor.top +
-                          (RECT_HEIGHT(monitorInfo.rcMonitor) - RECT_HEIGHT(windowRect)) / 2;
-        ::SetWindowPos(hwnd, nullptr, newX, newY, 0, 0,
-                       SWP_NOACTIVATE | SWP_NOSIZE | SWP_NOZORDER | SWP_NOOWNERZORDER);
-    }
-
     static inline void moveWindowToMonitor(HWND hwnd, const MONITORINFOEXW &activeMonitor) {
         RECT currentMonitorRect = getMonitorForWindow(hwnd).rcMonitor;
         RECT activeMonitorRect = activeMonitor.rcMonitor;
@@ -161,7 +156,7 @@
         [[maybe_unused]] const auto &cleaner =
             qScopeGuard([windowThreadProcessId, currentThreadId]() {
                 ::AttachThreadInput(windowThreadProcessId, currentThreadId, FALSE); //
-            });
+            }); // TODO: Remove it
 
         ::BringWindowToTop(hwnd);
         // Activate the window too. This will force us to the virtual desktop this
@@ -238,14 +233,15 @@
         apis.ptimeEndPeriod(ms_granularity);
     }
 
-    static void showSystemMenu2(HWND hWnd, const POINT &pos, const bool selectFirstEntry,
-                                const bool fixedSize) {
+    // Returns false if the menu is canceled
+    static bool showSystemMenu_sys(HWND hWnd, const POINT &pos, const bool selectFirstEntry,
+                                   const bool fixedSize) {
         HMENU hMenu = ::GetSystemMenu(hWnd, FALSE);
         if (!hMenu) {
             // The corresponding window doesn't have a system menu, most likely due to the
             // lack of the "WS_SYSMENU" window style. This situation should not be treated
             // as an error so just ignore it and return early.
-            return;
+            return true;
         }
 
         const bool maxOrFull = IsMaximized(hWnd) || isFullScreen(hWnd);
@@ -289,7 +285,8 @@
         // Popup the system menu at the required position.
         const auto result = ::TrackPopupMenu(
             hMenu,
-            (TPM_RETURNCMD | (QGuiApplication::isRightToLeft() ? TPM_RIGHTALIGN : TPM_LEFTALIGN)),
+            (TPM_RETURNCMD | (QGuiApplication::isRightToLeft() ? TPM_RIGHTALIGN : TPM_LEFTALIGN) |
+             TPM_RIGHTBUTTON),
             pos.x, pos.y, 0, hWnd, nullptr);
 
         // Unhighlight the first menu item after the popup menu is closed, otherwise it will keep
@@ -298,11 +295,12 @@
 
         if (!result) {
             // The user canceled the menu, no need to continue.
-            return;
+            return false;
         }
 
         // Send the command that the user chooses to the corresponding window.
         ::PostMessageW(hWnd, WM_SYSCOMMAND, result, 0);
+        return true;
     }
 
     static inline Win32WindowContext::WindowPart getHitWindowPart(int hitTestResult) {
@@ -329,7 +327,7 @@
             case HTBORDER:
                 return Win32WindowContext::FixedBorder;
             default:
-                // unreachable
+                Q_UNREACHABLE();
                 break;
         }
         return Win32WindowContext::Outside;
@@ -367,6 +365,107 @@
         return true;
     }
 
+    static inline constexpr bool isNonClientMessage(const UINT message) {
+        if (((message >= WM_NCCREATE) && (message <= WM_NCACTIVATE)) ||
+            ((message >= WM_NCMOUSEMOVE) && (message <= WM_NCMBUTTONDBLCLK)) ||
+            ((message >= WM_NCXBUTTONDOWN) && (message <= WM_NCXBUTTONDBLCLK))
+#if (WINVER >= _WIN32_WINNT_WIN8)
+            || ((message >= WM_NCPOINTERUPDATE) && (message <= WM_NCPOINTERUP))
+#endif
+            || ((message == WM_NCMOUSEHOVER) || (message == WM_NCMOUSELEAVE))) {
+            return true;
+        } else {
+            return false;
+        }
+    }
+
+    static MSG createMessageBlock(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam) {
+        MSG msg;
+        msg.hwnd = hWnd;       // re-create MSG structure
+        msg.message = message; // time and pt fields ignored
+        msg.wParam = wParam;
+        msg.lParam = lParam;
+
+        const DWORD dwScreenPos = ::GetMessagePos();
+        msg.pt.x = GET_X_LPARAM(dwScreenPos);
+        msg.pt.y = GET_Y_LPARAM(dwScreenPos);
+        if (!isNonClientMessage(message)) {
+            ::ScreenToClient(hWnd, &msg.pt);
+        }
+        return msg;
+    }
+
+    static inline constexpr bool isInputMessage(UINT m) {
+        switch (m) {
+            case WM_IME_STARTCOMPOSITION:
+            case WM_IME_ENDCOMPOSITION:
+            case WM_IME_COMPOSITION:
+            case WM_INPUT:
+            case WM_TOUCH:
+            case WM_MOUSEHOVER:
+            case WM_MOUSELEAVE:
+            case WM_NCMOUSEHOVER:
+            case WM_NCMOUSELEAVE:
+            case WM_SIZING:
+            case WM_MOVING:
+            case WM_SYSCOMMAND:
+            case WM_COMMAND:
+            case WM_DWMNCRENDERINGCHANGED:
+            case WM_PAINT:
+                return true;
+            default:
+                break;
+        }
+        return (m >= WM_MOUSEFIRST && m <= WM_MOUSELAST) ||
+               (m >= WM_NCMOUSEMOVE && m <= WM_NCXBUTTONDBLCLK) ||
+               (m >= WM_KEYFIRST && m <= WM_KEYLAST);
+    }
+
+    static inline QByteArray nativeEventType() {
+        return QByteArrayLiteral("windows_generic_MSG");
+    }
+
+    // Send to QAbstractEventDispatcher
+    bool filterNativeEvent(MSG *msg, LRESULT *result) {
+        auto dispatcher = QAbstractEventDispatcher::instance();
+        QT_NATIVE_EVENT_RESULT_TYPE filterResult = *result;
+        if (dispatcher && dispatcher->filterNativeEvent(nativeEventType(), msg, &filterResult)) {
+            *result = LRESULT(filterResult);
+            return true;
+        }
+        return false;
+    }
+
+    // Send to QWindowSystemInterface
+    bool filterNativeEvent(QWindow *window, MSG *msg, LRESULT *result) {
+        QT_NATIVE_EVENT_RESULT_TYPE filterResult = *result;
+        if (QWindowSystemInterface::handleNativeEvent(window, nativeEventType(), msg,
+                                                      &filterResult)) {
+            *result = LRESULT(filterResult);
+            return true;
+        }
+        return false;
+    }
+
+    static inline bool forwardFilteredEvent(QWindow *window, HWND hWnd, UINT message, WPARAM wParam,
+                                            LPARAM lParam, LRESULT *result) {
+        MSG msg = createMessageBlock(hWnd, message, wParam, lParam);
+
+        // https://github.com/qt/qtbase/blob/e26a87f1ecc40bc8c6aa5b889fce67410a57a702/src/plugins/platforms/windows/qwindowscontext.cpp#L1025
+        // Do exact the same as what Qt Windows plugin does.
+
+        // Run the native event filters. QTBUG-67095: Exclude input messages which are sent
+        // by QEventDispatcherWin32::processEvents()
+        if (!isInputMessage(msg.message) && filterNativeEvent(&msg, result))
+            return true;
+
+        auto platformWindow = window->handle();
+        if (platformWindow && filterNativeEvent(platformWindow->window(), &msg, result))
+            return true;
+
+        return false;
+    }
+
     // https://github.com/qt/qtbase/blob/e26a87f1ecc40bc8c6aa5b889fce67410a57a702/src/plugins/platforms/windows/qwindowscontext.cpp#L1556
     // In QWindowsContext::windowsProc(), the messages will be passed to all global native event
     // filters, but because we have already filtered the messages in the hook WndProc function for
@@ -386,17 +485,38 @@
                 return false;
             }
 
-            // https://github.com/qt/qtbase/blob/e26a87f1ecc40bc8c6aa5b889fce67410a57a702/src/plugins/platforms/windows/qwindowscontext.cpp#L1546
-            // Qt needs to refer to the WM_NCCALCSIZE message data that hasn't been processed, so we
-            // have to process it after Qt acquires the initial data.
             auto msg = static_cast<const MSG *>(message);
-            if (msg->message == WM_NCCALCSIZE && lastMessageContext) {
-                LRESULT res;
-                if (lastMessageContext->nonClientCalcSizeHandler(msg->hwnd, msg->message,
-                                                                 msg->wParam, msg->lParam, &res)) {
-                    *result = decltype(*result)(res);
-                    return true;
+            switch (msg->message) {
+                case WM_NCCALCSIZE: {
+                    // https://github.com/qt/qtbase/blob/e26a87f1ecc40bc8c6aa5b889fce67410a57a702/src/plugins/platforms/windows/qwindowscontext.cpp#L1546
+                    // Qt needs to refer to the WM_NCCALCSIZE message data that hasn't been
+                    // processed, so we have to process it after Qt acquires the initial data.
+                    if (lastMessageContext) {
+                        LRESULT res;
+                        if (lastMessageContext->nonClientCalcSizeHandler(
+                                msg->hwnd, msg->message, msg->wParam, msg->lParam, &res)) {
+                            *result = decltype(*result)(res);
+                            return true;
+                        }
+                    }
+                    break;
                 }
+
+                    // case WM_NCHITTEST: {
+                    //     // The child window must return HTTRANSPARENT when processing
+                    //     WM_NCHITTEST for
+                    //     // the parent window to receive WM_NCHITTEST.
+                    //     if (!lastMessageContext) {
+                    //         auto rootHWnd = ::GetAncestor(msg->hwnd, GA_ROOT);
+                    //         if (rootHWnd != msg->hwnd) {
+                    //             if (auto ctx = g_wndProcHash->value(rootHWnd)) {
+                    //                 *result = HTTRANSPARENT;
+                    //                 return true;
+                    //             }
+                    //         }
+                    //     }
+                    //     break;
+                    // }
             }
             return false;
         }
@@ -485,18 +605,24 @@
             return ::DefWindowProcW(hWnd, message, wParam, lParam);
         }
 
+        WindowsNativeEventFilter::lastMessageContext = ctx;
+        const auto &contextCleaner = qScopeGuard([]() {
+            WindowsNativeEventFilter::lastMessageContext = nullptr; //
+        });
+
         // Since Qt does the necessary processing of the WM_NCCALCSIZE message, we need to
         // forward it right away and process it in our native event filter.
         if (message == WM_NCCALCSIZE) {
-            WindowsNativeEventFilter::lastMessageContext = ctx;
-            LRESULT result = ::CallWindowProcW(g_qtWindowProc, hWnd, message, wParam, lParam);
-            WindowsNativeEventFilter::lastMessageContext = nullptr;
-            return result;
+            return ::CallWindowProcW(g_qtWindowProc, hWnd, message, wParam, lParam);
         }
 
         // Try hooked procedure and save result
         LRESULT result;
         if (ctx->windowProc(hWnd, message, wParam, lParam, &result)) {
+            // Forward the event to user-defined native event filters, there may be some messages
+            // that need to be processed by the user.
+            std::ignore =
+                forwardFilteredEvent(ctx->window(), hWnd, message, wParam, lParam, &result);
             return result;
         }
 
@@ -505,18 +631,10 @@
     }
 
     static inline void addManagedWindow(QWindow *window, HWND hWnd, Win32WindowContext *ctx) {
-        const auto margins = [hWnd]() -> QMargins {
-            const auto titleBarHeight = int(getTitleBarHeight(hWnd));
-            if (isSystemBorderEnabled()) {
-                return {0, -titleBarHeight, 0, 0};
-            } else {
-                const auto frameSize = int(getResizeBorderThickness(hWnd));
-                return {-frameSize, -titleBarHeight, -frameSize, -frameSize};
-            }
-        }();
-
-        // Inform Qt we want and have set custom margins
-        setInternalWindowFrameMargins(window, margins);
+        if (isSystemBorderEnabled()) {
+            // Inform Qt we want and have set custom margins
+            setInternalWindowFrameMargins(window, QMargins(0, -int(getTitleBarHeight(hWnd)), 0, 0));
+        }
 
         // Store original window proc
         if (!g_qtWindowProc) {
@@ -548,8 +666,8 @@
     }
 
     Win32WindowContext::~Win32WindowContext() {
-        if (windowId) {
-            removeManagedWindow(reinterpret_cast<HWND>(windowId));
+        if (m_windowId) {
+            removeManagedWindow(reinterpret_cast<HWND>(m_windowId));
         }
     }
 
@@ -559,36 +677,28 @@
 
     void Win32WindowContext::virtual_hook(int id, void *data) {
         switch (id) {
-            case CentralizeHook: {
-                if (!windowId)
-                    return;
-                const auto hwnd = reinterpret_cast<HWND>(windowId);
-                moveWindowToDesktopCenter(hwnd);
-                return;
-            }
-
             case RaiseWindowHook: {
-                if (!windowId)
+                if (!m_windowId)
                     return;
                 m_delegate->setWindowVisible(m_host, true);
-                const auto hwnd = reinterpret_cast<HWND>(windowId);
+                const auto hwnd = reinterpret_cast<HWND>(m_windowId);
                 bringWindowToFront(hwnd);
                 return;
             }
 
             case ShowSystemMenuHook: {
-                if (!windowId)
+                if (!m_windowId)
                     return;
                 const auto &pos = *static_cast<const QPoint *>(data);
-                auto hWnd = reinterpret_cast<HWND>(windowId);
+                auto hWnd = reinterpret_cast<HWND>(m_windowId);
 #if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
                 const QPoint nativeGlobalPos =
                     QHighDpi::toNativeGlobalPosition(pos, m_windowHandle);
 #else
                 const QPoint nativeGlobalPos = QHighDpi::toNativePixels(pos, m_windowHandle);
 #endif
-                showSystemMenu2(hWnd, qpoint2point(nativeGlobalPos), false,
-                                m_delegate->isHostSizeFixed(m_host));
+                std::ignore = showSystemMenu_sys(hWnd, qpoint2point(nativeGlobalPos), false,
+                                                 m_delegate->isHostSizeFixed(m_host));
                 return;
             }
 
@@ -602,16 +712,16 @@
                 return;
             }
 
-            case DrawWindows10BorderHook: {
 #if QWINDOWKIT_CONFIG(ENABLE_WINDOWS_SYSTEM_BORDERS)
-                if (!windowId)
+            case DrawWindows10BorderHook: {
+                if (!m_windowId)
                     return;
 
                 auto args = static_cast<void **>(data);
                 auto &painter = *static_cast<QPainter *>(args[0]);
                 const auto &rect = *static_cast<const QRect *>(args[1]);
                 const auto &region = *static_cast<const QRegion *>(args[2]);
-                const auto hwnd = reinterpret_cast<HWND>(windowId);
+                const auto hwnd = reinterpret_cast<HWND>(m_windowId);
 
                 QPen pen;
                 pen.setWidth(int(getWindowFrameBorderThickness(hwnd)) * 2);
@@ -643,20 +753,18 @@
                     QPoint{m_windowHandle->width(), 0}
                 });
                 painter.restore();
-#endif
                 return;
             }
 
             case DrawWindows10BorderHook2: {
-#if QWINDOWKIT_CONFIG(ENABLE_WINDOWS_SYSTEM_BORDERS)
-                if (!m_windowHandle)
+                if (!m_windowId)
                     return;
 
                 // https://github.com/microsoft/terminal/blob/71a6f26e6ece656084e87de1a528c4a8072eeabd/src/cascadia/WindowsTerminal/NonClientIslandWindow.cpp#L1025
                 // https://docs.microsoft.com/en-us/windows/win32/dwm/customframe#extending-the-client-frame
                 // Draw a black rectangle to make Windows native top border show
 
-                auto hWnd = reinterpret_cast<HWND>(windowId);
+                auto hWnd = reinterpret_cast<HWND>(m_windowId);
                 HDC hdc = ::GetDC(hWnd);
                 RECT windowRect{};
                 ::GetClientRect(hWnd, &windowRect);
@@ -669,9 +777,9 @@
                 ::FillRect(hdc, &rcTopBorder,
                            reinterpret_cast<HBRUSH>(::GetStockObject(BLACK_BRUSH)));
                 ::ReleaseDC(hWnd, hdc);
-#endif
                 return;
             }
+#endif
 
             default:
                 break;
@@ -681,11 +789,11 @@
 
     QVariant Win32WindowContext::windowAttribute(const QString &key) const {
         if (key == QStringLiteral("window-rect")) {
-            if (!m_windowHandle)
+            if (!m_windowId)
                 return {};
 
             RECT frame{};
-            auto hwnd = reinterpret_cast<HWND>(windowId);
+            auto hwnd = reinterpret_cast<HWND>(m_windowId);
             // According to MSDN, WS_OVERLAPPED is not allowed for AdjustWindowRect.
             auto style = static_cast<DWORD>(::GetWindowLongPtrW(hwnd, GWL_STYLE) & ~WS_OVERLAPPED);
             auto exStyle = static_cast<DWORD>(::GetWindowLongPtrW(hwnd, GWL_EXSTYLE));
@@ -704,29 +812,35 @@
         }
 
         if (key == QStringLiteral("border-thickness")) {
-            return m_windowHandle
-                       ? int(getWindowFrameBorderThickness(reinterpret_cast<HWND>(windowId)))
+            return m_windowId
+                       ? int(getWindowFrameBorderThickness(reinterpret_cast<HWND>(m_windowId)))
                        : 0;
         }
-
         return AbstractWindowContext::windowAttribute(key);
     }
 
-    void Win32WindowContext::winIdChanged() {
-        // If the original window id is valid, remove all resources related
-        if (windowId) {
-            removeManagedWindow(reinterpret_cast<HWND>(windowId));
-            windowId = 0;
+    void Win32WindowContext::winIdChanged(WId winId, WId oldWinId) {
+        // Reset the context data
+        mouseLeaveBlocked = false;
+        lastHitTestResult = WindowPart::Outside;
+        lastHitTestResultRaw = HTNOWHERE;
+
+        if (!isSystemBorderEnabled()) {
+            m_delegate->setWindowFlags(m_host, m_delegate->getWindowFlags(m_host) |
+                                                   Qt::FramelessWindowHint);
         }
 
-        if (!m_windowHandle) {
+        // If the original window id is valid, remove all resources related
+        if (oldWinId) {
+            removeManagedWindow(reinterpret_cast<HWND>(oldWinId));
+        }
+
+        if (!winId) {
             return;
         }
 
         // Install window hook
-        auto winId = m_windowHandle->winId();
         auto hWnd = reinterpret_cast<HWND>(winId);
-
         if (!isSystemBorderEnabled()) {
             static auto margins = QVariant::fromValue(QMargins(1, 1, 1, 1));
 
@@ -750,9 +864,6 @@
 
         // Add managed window
         addManagedWindow(m_windowHandle, hWnd, this);
-
-        // Cache win id
-        windowId = winId;
     }
 
     bool Win32WindowContext::windowProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam,
@@ -762,8 +873,8 @@
         // We should skip these messages otherwise we will get crashes.
         // NOTE: WM_QUIT won't be posted to the WindowProc function.
         switch (message) {
-            case WM_CLOSE:
             case WM_DESTROY:
+            case WM_CLOSE:
             case WM_NCDESTROY:
             // Undocumented messages:
             case WM_UAHDESTROYWINDOW:
@@ -794,13 +905,9 @@
 
         // Forward to native event filter subscribers
         if (!m_nativeEventFilters.isEmpty()) {
-            MSG msg;
-            msg.hwnd = hWnd;
-            msg.message = message;
-            msg.wParam = wParam;
-            msg.lParam = lParam;
+            MSG msg = createMessageBlock(hWnd, message, wParam, lParam);
             QT_NATIVE_EVENT_RESULT_TYPE res = 0;
-            if (nativeDispatch(QByteArrayLiteral("windows_generic_MSG"), &msg, &res)) {
+            if (nativeDispatch(nativeEventType(), &msg, &res)) {
                 *result = LRESULT(res);
                 return true;
             }
@@ -812,7 +919,7 @@
                                                     const QVariant &oldAttribute) {
         Q_UNUSED(oldAttribute)
 
-        const auto hwnd = reinterpret_cast<HWND>(m_windowHandle->winId());
+        const auto hwnd = reinterpret_cast<HWND>(m_windowId);
         const DynamicApis &apis = DynamicApis::instance();
         static constexpr const MARGINS extendedMargins = {-1, -1, -1, -1};
         const auto &restoreMargins = [this, &apis, hwnd]() {
@@ -1195,9 +1302,8 @@
     case WM_NCPOINTERUP:
 #endif
             case WM_NCMOUSEHOVER: {
-                const WindowPart currentWindowPart = lastHitTestResult;
                 if (message == WM_NCMOUSEMOVE) {
-                    if (currentWindowPart != WindowPart::ChromeButton) {
+                    if (lastHitTestResult != WindowPart::ChromeButton) {
                         // https://github.com/qt/qtbase/blob/e26a87f1ecc40bc8c6aa5b889fce67410a57a702/src/widgets/kernel/qwidgetwindow.cpp#L472
                         // When the mouse press event arrives, QWidgetWindow will implicitly grab
                         // the top widget right under the mouse, and set `qt_button_down` to this
@@ -1246,29 +1352,38 @@
                         // the above problems would not arise.
 
                         m_delegate->resetQtGrabbedControl(m_host);
+
+                        // If the mouse moves from chrome buttons to other non-client areas, a
+                        // WM_MOUSELEAVE message should be sent.
                         if (mouseLeaveBlocked) {
                             emulateClientAreaMessage(hWnd, message, wParam, lParam,
                                                      WM_NCMOUSELEAVE);
                         }
                     }
-
-                    // We need to make sure we get the right hit-test result when a WM_NCMOUSELEAVE
-                    // comes, so we reset it when we receive a WM_NCMOUSEMOVE.
-
-                    // If the mouse is entering the client area, there must be a WM_NCHITTEST
-                    // setting it to `Client` before the WM_NCMOUSELEAVE comes; if the mouse is
-                    // leaving the window, current window part remains as `Outside`.
-                    lastHitTestResult = WindowPart::Outside;
                 }
 
-                if (currentWindowPart == WindowPart::ChromeButton) {
-                    emulateClientAreaMessage(hWnd, message, wParam, lParam);
+                if (lastHitTestResult == WindowPart::ChromeButton) {
                     if (message == WM_NCMOUSEMOVE) {
                         // ### FIXME FIXME FIXME
                         // ### FIXME: Calling DefWindowProc() here is really dangerous, investigate
                         // how to avoid doing this.
                         // ### FIXME FIXME FIXME
                         *result = ::DefWindowProcW(hWnd, WM_NCMOUSEMOVE, wParam, lParam);
+                    } else if (lastHitTestResultRaw == HTSYSMENU) {
+                        if (message == WM_NCLBUTTONDOWN) {
+                            // A message of WM_SYSCOMMAND with SC_MOUSEMENU will be sent by Windows,
+                            // and the current control flow will be blocked by the menu while
+                            // Windows will create and execute a new event loop until the menu
+                            // returns
+                            iconButtonClickTime = ::GetTickCount64();
+                            *result = ::DefWindowProcW(hWnd, message, wParam, lParam);
+                            iconButtonClickTime = 0;
+                        } else if (message == WM_NCLBUTTONDBLCLK) {
+                            // A message of WM_SYSCOMMAND with SC_CLOSE will be sent by Windows
+                            *result = ::DefWindowProcW(hWnd, message, wParam, lParam);
+                        } else {
+                            *result = FALSE;
+                        }
                     } else {
                         // According to MSDN, we should return non-zero for X button messages to
                         // indicate we have handled these messages (due to historical reasons), for
@@ -1278,6 +1393,7 @@
                                  ? TRUE
                                  : FALSE);
                     }
+                    emulateClientAreaMessage(hWnd, message, wParam, lParam);
                     return true;
                 }
                 break;
@@ -1290,7 +1406,7 @@
                     // pressing area as HTCLIENT which maybe because of our former retransmission of
                     // WM_NCLBUTTONDOWN, as a result, a WM_NCMOUSELEAVE will come immediately and a
                     // lot of WM_MOUSEMOVE will come if we move the mouse, we should track the mouse
-                    // in advance.
+                    // in advance. (May be redundant?)
                     if (mouseLeaveBlocked) {
                         mouseLeaveBlocked = false;
                         requestForMouseLeaveMessage(hWnd, false);
@@ -1324,19 +1440,6 @@
     bool Win32WindowContext::customWindowHandler(HWND hWnd, UINT message, WPARAM wParam,
                                                  LPARAM lParam, LRESULT *result) {
         switch (message) {
-            case WM_SHOWWINDOW: {
-                if (!initialCentered) {
-                    // If wParam is TRUE, the window is being shown.
-                    // If lParam is zero, the message was sent because of a call to the ShowWindow
-                    // function.
-                    if (wParam && !lParam) {
-                        initialCentered = true;
-                        moveWindowToDesktopCenter(hWnd);
-                    }
-                }
-                break;
-            }
-
             case WM_NCHITTEST: {
                 // 鍘熺敓Win32绐楀彛鍙湁椤惰竟鏄湪绐楀彛鍐呴儴resize鐨勶紝鍏朵綑涓夎竟閮芥槸鍦ㄧ獥鍙�
                 // 澶栭儴杩涜resize鐨勶紝鍏跺師鐞嗘槸锛學S_THICKFRAME杩欎釜绐楀彛鏍峰紡浼氬湪绐�
@@ -1419,7 +1522,8 @@
                 // color, our homemade top border can almost have exactly the same
                 // appearance with the system's one.
                 [[maybe_unused]] const auto &hitTestRecorder = qScopeGuard([this, result]() {
-                    lastHitTestResult = getHitWindowPart(int(*result)); //
+                    lastHitTestResultRaw = int(*result);
+                    lastHitTestResult = getHitWindowPart(lastHitTestResultRaw);
                 });
 
                 POINT nativeGlobalPos{GET_X_LPARAM(lParam), GET_Y_LPARAM(lParam)};
@@ -1968,6 +2072,7 @@
         bool shouldShowSystemMenu = false;
         bool broughtByKeyboard = false;
         POINT nativeGlobalPos{};
+
         switch (message) {
             case WM_RBUTTONUP: {
                 const POINT nativeLocalPos = getNativePosFromMouse();
@@ -1989,10 +2094,20 @@
             }
             case WM_SYSCOMMAND: {
                 const WPARAM filteredWParam = (wParam & 0xFFF0);
-                if ((filteredWParam == SC_KEYMENU) && (lParam == VK_SPACE)) {
-                    shouldShowSystemMenu = true;
-                    broughtByKeyboard = true;
-                    nativeGlobalPos = getNativeGlobalPosFromKeyboard();
+                switch (filteredWParam) {
+                    case SC_MOUSEMENU:
+                        shouldShowSystemMenu = true;
+                        nativeGlobalPos = getNativeGlobalPosFromKeyboard();
+                        break;
+                    case SC_KEYMENU:
+                        if (lParam == VK_SPACE) {
+                            shouldShowSystemMenu = true;
+                            broughtByKeyboard = true;
+                            nativeGlobalPos = getNativeGlobalPosFromKeyboard();
+                        }
+                        break;
+                    default:
+                        break;
                 }
                 break;
             }
@@ -2011,8 +2126,31 @@
                 break;
         }
         if (shouldShowSystemMenu) {
-            showSystemMenu2(hWnd, nativeGlobalPos, broughtByKeyboard,
-                            m_delegate->isHostSizeFixed(m_host));
+            bool triggeredByIconButton = iconButtonClickTime > 0;
+            if (triggeredByIconButton) {
+                // TODO: Adjust `nativeGlobalPos` to (0, realTitleBarHeight)
+                // hint: use m_delgegate->mapGeometryToScene
+            }
+            bool res = showSystemMenu_sys(hWnd, nativeGlobalPos, broughtByKeyboard,
+                                          m_delegate->isHostSizeFixed(m_host));
+
+            // Emulate the Windows SYSMENU button's behavior
+            static uint32_t doubleClickTime = ::GetDoubleClickTime();
+            if (triggeredByIconButton && !res &&
+                ::GetTickCount64() - iconButtonClickTime <= doubleClickTime) {
+                POINT nativeGlobalPos;
+                ::GetCursorPos(&nativeGlobalPos);
+                POINT nativeLocalPos = nativeGlobalPos;
+                ::ScreenToClient(hWnd, &nativeLocalPos);
+                QPoint qtScenePos =
+                    QHighDpi::fromNativeLocalPosition(point2qpoint(nativeLocalPos), m_windowHandle);
+                WindowAgentBase::SystemButton sysButtonType = WindowAgentBase::Unknown;
+                if (isInSystemButtons(qtScenePos, &sysButtonType) &&
+                    sysButtonType == WindowAgentBase::WindowIcon) {
+                    ::PostMessageW(hWnd, WM_SYSCOMMAND, SC_CLOSE, 0);
+                }
+            }
+
             // QPA's internal code will handle system menu events separately, and its
             // behavior is not what we would want to see because it doesn't know our
             // window doesn't have any window frame now, so return early here to avoid

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