From 5e1c012c539e74804454d45a1b945093afdb8f4f Mon Sep 17 00:00:00 2001
From: Zhao Yuhang <2546789017@qq.com>
Date: 周日, 09 2月 2025 11:15:59 +0800
Subject: [PATCH] apply some fixes and workarounds

---
 src/core/contexts/win32windowcontext.cpp |  488 ++++++++++++++++++++++++++++++++++-------------------
 1 files changed, 311 insertions(+), 177 deletions(-)

diff --git a/src/core/contexts/win32windowcontext.cpp b/src/core/contexts/win32windowcontext.cpp
index 93a186c..204b4b0 100644
--- a/src/core/contexts/win32windowcontext.cpp
+++ b/src/core/contexts/win32windowcontext.cpp
@@ -33,7 +33,17 @@
 #include "qwkglobal_p.h"
 #include "qwkwindowsextra_p.h"
 
+#if (QT_VERSION >= QT_VERSION_CHECK(6, 6, 0)) && (QT_VERSION <= QT_VERSION_CHECK(6, 6, 1))
+#  error Current Qt version has a critical bug which will break QWK functionality. Please upgrade to > 6.6.1 or downgrade to < 6.6.0
+#endif
+
 namespace QWK {
+
+    enum IconButtonClickLevelFlag {
+        IconButtonClicked = 1,
+        IconButtonDoubleClicked = 2,
+        IconButtonTriggersClose = 4,
+    };
 
     // The thickness of an auto-hide taskbar in pixels.
     static constexpr const quint8 kAutoHideTaskBarThickness = 2;
@@ -75,6 +85,8 @@
 
     static void setInternalWindowFrameMargins(QWindow *window, const QMargins &margins) {
         const QVariant marginsVar = QVariant::fromValue(margins);
+
+        // TODO: Add comments
         window->setProperty("_q_windowsCustomMargins", marginsVar);
 #if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
         if (QPlatformWindow *platformWindow = window->handle()) {
@@ -118,6 +130,36 @@
                        SWP_NOACTIVATE | SWP_NOSIZE | SWP_NOZORDER | SWP_NOOWNERZORDER);
     }
 
+    static inline bool isFullScreen(HWND hwnd) {
+        RECT windowRect{};
+        ::GetWindowRect(hwnd, &windowRect);
+        // Compare to the full area of the screen, not the work area.
+        return (windowRect == getMonitorForWindow(hwnd).rcMonitor);
+    }
+
+    static inline bool isMaximized(HWND hwnd) {
+        return ::IsZoomed(hwnd);
+    }
+
+    static inline bool isMinimized(HWND hwnd) {
+        return ::IsIconic(hwnd);
+    }
+
+    static inline bool isWindowNoState(HWND hwnd) {
+#if 0
+        WINDOWPLACEMENT wp{};
+        wp.length = sizeof(wp);
+        ::GetWindowPlacement(hwnd, &wp);
+        return ((wp.showCmd == SW_NORMAL) || (wp.showCmd == SW_RESTORE));
+#else
+        if (isFullScreen(hwnd)) {
+            return false;
+        }
+        const auto style = static_cast<DWORD>(::GetWindowLongPtrW(hwnd, GWL_STYLE));
+        return (!(style & (WS_MINIMIZE | WS_MAXIMIZE)));
+#endif
+    }
+
     static inline void bringWindowToFront(HWND hwnd) {
         HWND oldForegroundWindow = ::GetForegroundWindow();
         if (!oldForegroundWindow) {
@@ -129,7 +171,7 @@
         if (!::IsWindowVisible(hwnd)) {
             ::ShowWindow(hwnd, SW_SHOW);
         }
-        if (IsMinimized(hwnd)) {
+        if (isMinimized(hwnd)) {
             // Restore the window if it is minimized.
             ::ShowWindow(hwnd, SW_RESTORE);
             // Once we've been restored, throw us on the active monitor.
@@ -166,73 +208,6 @@
         moveWindowToMonitor(hwnd, activeMonitor);
     }
 
-    static inline bool isFullScreen(HWND hwnd) {
-        RECT windowRect{};
-        ::GetWindowRect(hwnd, &windowRect);
-        // Compare to the full area of the screen, not the work area.
-        return (windowRect == getMonitorForWindow(hwnd).rcMonitor);
-    }
-
-    static inline bool isWindowNoState(HWND hwnd) {
-#if 0
-        WINDOWPLACEMENT wp{};
-        wp.length = sizeof(wp);
-        ::GetWindowPlacement(hwnd, &wp);
-        return ((wp.showCmd == SW_NORMAL) || (wp.showCmd == SW_RESTORE));
-#else
-        if (isFullScreen(hwnd)) {
-            return false;
-        }
-        const auto style = static_cast<DWORD>(::GetWindowLongPtrW(hwnd, GWL_STYLE));
-        return (!(style & (WS_MINIMIZE | WS_MAXIMIZE)));
-#endif
-    }
-
-    static void syncPaintEventWithDwm() {
-        // No need to sync with DWM if DWM composition is disabled.
-        if (!isDwmCompositionEnabled()) {
-            return;
-        }
-        const DynamicApis &apis = DynamicApis::instance();
-        // Dirty hack to workaround the resize flicker caused by DWM.
-        LARGE_INTEGER freq{};
-        ::QueryPerformanceFrequency(&freq);
-        TIMECAPS tc{};
-        apis.ptimeGetDevCaps(&tc, sizeof(tc));
-        const UINT ms_granularity = tc.wPeriodMin;
-        apis.ptimeBeginPeriod(ms_granularity);
-        LARGE_INTEGER now0{};
-        ::QueryPerformanceCounter(&now0);
-        // ask DWM where the vertical blank falls
-        DWM_TIMING_INFO dti{};
-        dti.cbSize = sizeof(dti);
-        apis.pDwmGetCompositionTimingInfo(nullptr, &dti);
-        LARGE_INTEGER now1{};
-        ::QueryPerformanceCounter(&now1);
-        // - DWM told us about SOME vertical blank
-        //   - past or future, possibly many frames away
-        // - convert that into the NEXT vertical blank
-        const auto period = qreal(dti.qpcRefreshPeriod);
-        const auto dt = qreal(dti.qpcVBlank - now1.QuadPart);
-        const qreal ratio = (dt / period);
-        auto w = qreal(0);
-        auto m = qreal(0);
-        if ((dt > qreal(0)) || qFuzzyIsNull(dt)) {
-            w = ratio;
-        } else {
-            // reach back to previous period
-            // - so m represents consistent position within phase
-            w = (ratio - qreal(1));
-        }
-        m = (dt - (period * w));
-        if ((m < qreal(0)) || qFuzzyCompare(m, period) || (m > period)) {
-            return;
-        }
-        const qreal m_ms = (qreal(1000) * m / qreal(freq.QuadPart));
-        ::Sleep(static_cast<DWORD>(std::round(m_ms)));
-        apis.ptimeEndPeriod(ms_granularity);
-    }
-
     // Returns false if the menu is canceled
     static bool showSystemMenu_sys(HWND hWnd, const POINT &pos, const bool selectFirstEntry,
                                    const bool fixedSize) {
@@ -244,7 +219,7 @@
             return true;
         }
 
-        const bool maxOrFull = IsMaximized(hWnd) || isFullScreen(hWnd);
+        const bool maxOrFull = isMaximized(hWnd) || isFullScreen(hWnd);
         ::EnableMenuItem(hMenu, SC_CLOSE, (MF_BYCOMMAND | MFS_ENABLED));
         ::EnableMenuItem(hMenu, SC_MAXIMIZE,
                          (MF_BYCOMMAND | ((maxOrFull || fixedSize) ? MFS_DISABLED : MFS_ENABLED)));
@@ -327,7 +302,6 @@
             case HTBORDER:
                 return Win32WindowContext::FixedBorder;
             default:
-                Q_UNREACHABLE();
                 break;
         }
         return Win32WindowContext::Outside;
@@ -619,6 +593,7 @@
         // Try hooked procedure and save result
         LRESULT result;
         if (ctx->windowProc(hWnd, message, wParam, lParam, &result)) {
+            // https://github.com/stdware/qwindowkit/issues/45
             // Forward the event to user-defined native event filters, there may be some messages
             // that need to be processed by the user.
             std::ignore =
@@ -693,12 +668,12 @@
                 auto hWnd = reinterpret_cast<HWND>(m_windowId);
 #if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
                 const QPoint nativeGlobalPos =
-                    QHighDpi::toNativeGlobalPosition(pos, m_windowHandle);
+                    QHighDpi::toNativeGlobalPosition(pos, m_windowHandle.data());
 #else
-                const QPoint nativeGlobalPos = QHighDpi::toNativePixels(pos, m_windowHandle);
+                const QPoint nativeGlobalPos = QHighDpi::toNativePixels(pos, m_windowHandle.data());
 #endif
                 std::ignore = showSystemMenu_sys(hWnd, qpoint2point(nativeGlobalPos), false,
-                                                 m_delegate->isHostSizeFixed(m_host));
+                                                 isHostSizeFixed());
                 return;
             }
 
@@ -811,10 +786,18 @@
             return isSystemBorderEnabled() && !isWin11OrGreater();
         }
 
+        if (key == QStringLiteral("windows-system-border-enabled")) {
+            return isSystemBorderEnabled();
+        }
+
         if (key == QStringLiteral("border-thickness")) {
             return m_windowId
                        ? int(getWindowFrameBorderThickness(reinterpret_cast<HWND>(m_windowId)))
                        : 0;
+        }
+
+        if (key == QStringLiteral("title-bar-height")) {
+            return m_windowId ? int(getTitleBarHeight(reinterpret_cast<HWND>(m_windowId))) : 0;
         }
         return AbstractWindowContext::windowAttribute(key);
     }
@@ -825,16 +808,10 @@
         lastHitTestResult = WindowPart::Outside;
         lastHitTestResultRaw = HTNOWHERE;
 
-        if (!isSystemBorderEnabled()) {
-            m_delegate->setWindowFlags(m_host, m_delegate->getWindowFlags(m_host) |
-                                                   Qt::FramelessWindowHint);
-        }
-
         // If the original window id is valid, remove all resources related
         if (oldWinId) {
             removeManagedWindow(reinterpret_cast<HWND>(oldWinId));
         }
-
         if (!winId) {
             return;
         }
@@ -920,8 +897,40 @@
         Q_UNUSED(oldAttribute)
 
         const auto hwnd = reinterpret_cast<HWND>(m_windowId);
+        Q_ASSERT(hwnd);
+        if (!hwnd) {
+            return false;
+        }
+
         const DynamicApis &apis = DynamicApis::instance();
-        static constexpr const MARGINS extendedMargins = {-1, -1, -1, -1};
+        const auto &extendMargins = [this, &apis, hwnd]() {
+            // For some unknown reason, the window background is totally black when the host object
+            // is a QWidget. And extending the window frame into the client area seems to fix it
+            // magically.
+            // We don't need the following *HACK* for QtQuick windows.
+            if (!m_host->isWidgetType()) {
+                return;
+            }
+            // After many times of trying, we found that the Acrylic/Mica/Mica Alt background
+            // only appears on the native Win32 window's background, so naturally we want to
+            // extend the window frame into the whole client area to be able to let the special
+            // material fill the whole window. Previously we are using negative margins because
+            // it's widely known that using negative margins will let the window frame fill
+            // the whole window and that's indeed what we wanted to do, however, later we found
+            // that doing so is causing issues. When the user enabled the "show accent color on
+            // window title bar and borders" option on system personalize settings, a 30px bar
+            // would appear on window top. It has the same color with the system accent color.
+            // Actually it's the original title bar we've already hidden, and it magically
+            // appears again when we use negative margins to extend the window frame. And again
+            // after some experiments, I found that the title bar won't appear if we don't extend
+            // from the top side. In the end I found that we only need to extend from the left
+            // side if we extend long enough. In this way we can see the special material even
+            // when the host object is a QWidget and the title bar still remain hidden. But even
+            // though this solution seems perfect, I really don't know why it works. The following
+            // hack is totally based on experiments.
+            static constexpr const MARGINS margins = {65536, 0, 0, 0};
+            apis.pDwmExtendFrameIntoClientArea(hwnd, &margins);
+        };
         const auto &restoreMargins = [this, &apis, hwnd]() {
             auto margins = qmargins2margins(
                 m_windowAttributes.value(QStringLiteral("extra-margins")).value<QMargins>());
@@ -930,7 +939,7 @@
 
         if (key == QStringLiteral("extra-margins")) {
             auto margins = qmargins2margins(attribute.value<QMargins>());
-            return apis.pDwmExtendFrameIntoClientArea(hwnd, &margins) == S_OK;
+            return SUCCEEDED(apis.pDwmExtendFrameIntoClientArea(hwnd, &margins));
         }
 
         if (key == QStringLiteral("dark-mode")) {
@@ -944,12 +953,8 @@
             } else {
                 apis.pAllowDarkModeForApp(enable);
             }
-            for (const auto attr : {
-                     _DWMWA_USE_IMMERSIVE_DARK_MODE_BEFORE_20H1,
-                     _DWMWA_USE_IMMERSIVE_DARK_MODE,
-                 }) {
-                apis.pDwmSetWindowAttribute(hwnd, attr, &enable, sizeof(enable));
-            }
+            const auto attr = isWin1020H1OrGreater() ? _DWMWA_USE_IMMERSIVE_DARK_MODE : _DWMWA_USE_IMMERSIVE_DARK_MODE_BEFORE_20H1;
+            apis.pDwmSetWindowAttribute(hwnd, attr, &enable, sizeof(enable));
 
             apis.pFlushMenuThemes();
             return true;
@@ -961,9 +966,7 @@
                 return false;
             }
             if (attribute.toBool()) {
-                // We need to extend the window frame into the whole client area to be able
-                // to see the blurred window background.
-                apis.pDwmExtendFrameIntoClientArea(hwnd, &extendedMargins);
+                extendMargins();
                 if (isWin1122H2OrGreater()) {
                     // Use official DWM API to enable Mica, available since Windows 11 22H2
                     // (10.0.22621).
@@ -995,9 +998,7 @@
                 return false;
             }
             if (attribute.toBool()) {
-                // We need to extend the window frame into the whole client area to be able
-                // to see the blurred window background.
-                apis.pDwmExtendFrameIntoClientArea(hwnd, &extendedMargins);
+                extendMargins();
                 // Use official DWM API to enable Mica Alt, available since Windows 11 22H2
                 // (10.0.22621).
                 const _DWM_SYSTEMBACKDROP_TYPE backdropType = _DWMSBT_TABBEDWINDOW;
@@ -1017,9 +1018,7 @@
                 return false;
             }
             if (attribute.toBool()) {
-                // We need to extend the window frame into the whole client area to be able
-                // to see the blurred window background.
-                apis.pDwmExtendFrameIntoClientArea(hwnd, &extendedMargins);
+                extendMargins();
 
                 const _DWM_SYSTEMBACKDROP_TYPE backdropType = _DWMSBT_TRANSIENTWINDOW;
                 apis.pDwmSetWindowAttribute(hwnd, _DWMWA_SYSTEMBACKDROP_TYPE, &backdropType,
@@ -1060,9 +1059,9 @@
         }
 
         if (key == QStringLiteral("dwm-blur")) {
+            // Extending window frame would break this effect for some unknown reason.
+            restoreMargins();
             if (attribute.toBool()) {
-                // We can't extend the window frame for this effect.
-                restoreMargins();
                 if (isWin8OrGreater()) {
                     ACCENT_POLICY policy{};
                     policy.dwAccentState = ACCENT_ENABLE_BLURBEHIND;
@@ -1257,7 +1256,7 @@
                     POINT screenPoint{GET_X_LPARAM(dwScreenPos), GET_Y_LPARAM(dwScreenPos)};
                     ::ScreenToClient(hWnd, &screenPoint);
                     QPoint qtScenePos = QHighDpi::fromNativeLocalPosition(point2qpoint(screenPoint),
-                                                                          m_windowHandle);
+                                                                          m_windowHandle.data());
                     auto dummy = WindowAgentBase::Unknown;
                     if (isInSystemButtons(qtScenePos, &dummy)) {
                         // We must record whether the last WM_MOUSELEAVE was filtered, because if
@@ -1382,13 +1381,17 @@
                                     // menu while Windows will create and execute a new event loop
                                     // until the menu returns
                                     iconButtonClickTime = ::GetTickCount64();
-                                    *result =
-                                        ::DefWindowProcW(hWnd, WM_NCLBUTTONDOWN, wParam, lParam);
-                                    if (iconButtonClickLevel == 2) {
+                                    *result = ::DefWindowProcW(hWnd, message, wParam, lParam);
+                                    iconButtonClickTime = 0;
+                                    if (iconButtonClickLevel & IconButtonTriggersClose) {
                                         ::PostMessageW(hWnd, WM_SYSCOMMAND, SC_CLOSE, 0);
                                     }
-                                    // No need to reset `iconButtonClickLevel`, if it has value,
-                                    // there must be another incoming WM_NCLBUTTONDOWN
+                                    if (iconButtonClickLevel & IconButtonDoubleClicked) {
+                                        iconButtonClickLevel = 0;
+                                    }
+                                    // Otherwise, no need to reset `iconButtonClickLevel` if not to
+                                    // close, if it has value, there must be another incoming
+                                    // WM_NCLBUTTONDOWN
                                 } else {
                                     iconButtonClickLevel = 0;
                                 }
@@ -1553,15 +1556,24 @@
                 auto clientWidth = RECT_WIDTH(clientRect);
                 auto clientHeight = RECT_HEIGHT(clientRect);
 
-                QPoint qtScenePos =
-                    QHighDpi::fromNativeLocalPosition(point2qpoint(nativeLocalPos), m_windowHandle);
+                QPoint qtScenePos = QHighDpi::fromNativeLocalPosition(point2qpoint(nativeLocalPos),
+                                                                      m_windowHandle.data());
 
-                bool isFixedSize = m_delegate->isHostSizeFixed(m_host);
-                bool isTitleBar = isInTitleBarDraggableArea(qtScenePos);
+                int frameSize = getResizeBorderThickness(hWnd);
+
+                bool isFixedWidth = isHostWidthFixed();
+                bool isFixedHeight = isHostHeightFixed();
+                bool isFixedSize = isHostSizeFixed();
+                bool isInLeftBorder = nativeLocalPos.x <= frameSize;
+                bool isInTopBorder = nativeLocalPos.y <= frameSize;
+                bool isInRightBorder = nativeLocalPos.x > clientWidth - frameSize;
+                bool isInBottomBorder = nativeLocalPos.y > clientHeight - frameSize;
+                bool isInTitleBar = isInTitleBarDraggableArea(qtScenePos);
+                WindowAgentBase::SystemButton sysButtonType = WindowAgentBase::Unknown;
+                bool isInCaptionButtons = isInSystemButtons(qtScenePos, &sysButtonType);
                 bool dontOverrideCursor = false; // ### TODO
 
-                WindowAgentBase::SystemButton sysButtonType = WindowAgentBase::Unknown;
-                if (!isFixedSize && isInSystemButtons(qtScenePos, &sysButtonType)) {
+                if (isInCaptionButtons) {
                     // Firstly, we set the hit test result to a default value to be able to detect
                     // whether we have changed it or not afterwards.
                     *result = HTNOWHERE;
@@ -1571,29 +1583,41 @@
                     // window is not maximized/fullscreen/minimized, of course).
                     if (isWindowNoState(hWnd)) {
                         static constexpr const quint8 kBorderSize = 2;
-                        bool isTop = (nativeLocalPos.y <= kBorderSize);
+                        bool isTop = nativeLocalPos.y <= kBorderSize;
                         bool isLeft = nativeLocalPos.x <= kBorderSize;
-                        bool isRight = (nativeLocalPos.x >= (clientWidth - kBorderSize));
+                        bool isRight = nativeLocalPos.x > clientWidth - kBorderSize;
                         if (isTop || isLeft || isRight) {
-                            if (dontOverrideCursor) {
+                            if (isFixedSize || dontOverrideCursor) {
                                 // The user doesn't want the window to be resized, so we tell
                                 // Windows we are in the client area so that the controls beneath
                                 // the mouse cursor can still be hovered or clicked.
-                                *result = (isTitleBar ? HTCAPTION : HTCLIENT);
+                                *result = isInTitleBar ? HTCAPTION : HTCLIENT;
                             } else {
                                 if (isTop) {
                                     if (isLeft) {
-                                        *result = HTTOPLEFT;
+                                        if (isFixedWidth) {
+                                            *result = HTTOP;
+                                        } else if (isFixedHeight) {
+                                            *result = HTLEFT;
+                                        } else {
+                                            *result = HTTOPLEFT;
+                                        }
                                     } else if (isRight) {
-                                        *result = HTTOPRIGHT;
+                                        if (isFixedWidth) {
+                                            *result = HTTOP;
+                                        } else if (isFixedHeight) {
+                                            *result = HTRIGHT;
+                                        } else {
+                                            *result = HTTOPRIGHT;
+                                        }
                                     } else {
-                                        *result = HTTOP;
+                                        *result = isFixedHeight ? HTBORDER : HTTOP;
                                     }
                                 } else {
-                                    if (isLeft) {
-                                        *result = HTLEFT;
+                                    if (isFixedWidth) {
+                                        *result = HTBORDER;
                                     } else {
-                                        *result = HTRIGHT;
+                                        *result = isLeft ? HTLEFT : HTRIGHT;
                                     }
                                 }
                             }
@@ -1635,10 +1659,8 @@
                 // OK, we are not inside any chrome buttons, try to find out which part of the
                 // window are we hitting.
 
-                bool max = IsMaximized(hWnd);
+                bool max = isMaximized(hWnd);
                 bool full = isFullScreen(hWnd);
-                int frameSize = getResizeBorderThickness(hWnd);
-                bool isTop = (nativeLocalPos.y < frameSize);
 
                 if (isSystemBorderEnabled()) {
                     // This will handle the left, right and bottom parts of the frame
@@ -1650,8 +1672,51 @@
                         // outside the window, that is, the three transparent window resize area.
                         // Returning HTCLIENT will confuse Windows, we can't put our controls there
                         // anyway.
-                        *result = ((isFixedSize || dontOverrideCursor) ? HTBORDER
-                                                                       : originalHitTestResult);
+                        *result = HTNOWHERE; // Make sure we can know we don't set any value
+                                             // explicitly later.
+                        if (originalHitTestResult == HTCAPTION) {
+                        } else if (isFixedSize || dontOverrideCursor) {
+                            *result = HTBORDER;
+                        } else if (isFixedWidth || isFixedHeight) {
+                            if (originalHitTestResult == HTTOPLEFT) {
+                                if (isFixedWidth) {
+                                    *result = HTTOP;
+                                } else {
+                                    *result = HTLEFT;
+                                }
+                            } else if (originalHitTestResult == HTTOPRIGHT) {
+                                if (isFixedWidth) {
+                                    *result = HTTOP;
+                                } else {
+                                    *result = HTRIGHT;
+                                }
+                            } else if (originalHitTestResult == HTBOTTOMRIGHT) {
+                                if (isFixedWidth) {
+                                    *result = HTBOTTOM;
+                                } else {
+                                    *result = HTRIGHT;
+                                }
+                            } else if (originalHitTestResult == HTBOTTOMLEFT) {
+                                if (isFixedWidth) {
+                                    *result = HTBOTTOM;
+                                } else {
+                                    *result = HTLEFT;
+                                }
+                            } else if (originalHitTestResult == HTLEFT ||
+                                       originalHitTestResult == HTRIGHT) {
+                                if (isFixedWidth) {
+                                    *result = HTBORDER;
+                                }
+                            } else if (originalHitTestResult == HTTOP ||
+                                       originalHitTestResult == HTBOTTOM) {
+                                if (isFixedHeight) {
+                                    *result = HTBORDER;
+                                }
+                            }
+                        }
+                        if (*result == HTNOWHERE) {
+                            *result = originalHitTestResult;
+                        }
                         return true;
                     }
                     if (full) {
@@ -1659,7 +1724,7 @@
                         return true;
                     }
                     if (max) {
-                        *result = (isTitleBar ? HTCAPTION : HTCLIENT);
+                        *result = isInTitleBar ? HTCAPTION : HTCLIENT;
                         return true;
                     }
                     // At this point, we know that the cursor is inside the client area,
@@ -1667,16 +1732,25 @@
                     // title bar or the drag bar. Apparently, it must be the drag bar or
                     // the little border at the top which the user can use to move or
                     // resize the window.
-                    if (isTop) {
+                    if (isInTopBorder) {
                         // Return HTCLIENT instead of HTBORDER here, because the mouse is
                         // inside our homemade title bar now, return HTCLIENT to let our
                         // title bar can still capture mouse events.
-                        *result = ((isFixedSize || dontOverrideCursor)
-                                       ? (isTitleBar ? HTCAPTION : HTCLIENT)
-                                       : HTTOP);
+                        *result = [&]() {
+                            if (isFixedSize || isFixedHeight || dontOverrideCursor ||
+                                (isFixedWidth && (isInLeftBorder || isInRightBorder))) {
+                                if (isInTitleBar) {
+                                    return HTCAPTION;
+                                } else {
+                                    return HTCLIENT;
+                                }
+                            } else {
+                                return HTTOP;
+                            }
+                        }();
                         return true;
                     }
-                    if (isTitleBar) {
+                    if (isInTitleBar) {
                         *result = HTCAPTION;
                         return true;
                     }
@@ -1687,58 +1761,86 @@
                         *result = HTCLIENT;
                         return true;
                     }
-                    if (max) {
-                        *result = (isTitleBar ? HTCAPTION : HTCLIENT);
+                    if (max || isFixedSize || dontOverrideCursor) {
+                        *result = isInTitleBar ? HTCAPTION : HTCLIENT;
                         return true;
                     }
-                    if (!isFixedSize) {
-                        const bool isBottom = (nativeLocalPos.y >= (clientHeight - frameSize));
-                        // Make the border a little wider to let the user easy to resize on corners.
-                        const auto scaleFactor = ((isTop || isBottom) ? qreal(2) : qreal(1));
-                        const int scaledFrameSize = std::round(qreal(frameSize) * scaleFactor);
-                        const bool isLeft = (nativeLocalPos.x < scaledFrameSize);
-                        const bool isRight = (nativeLocalPos.x >= (clientWidth - scaledFrameSize));
-                        if (dontOverrideCursor && (isTop || isBottom || isLeft || isRight)) {
-                            // Return HTCLIENT instead of HTBORDER here, because the mouse is
-                            // inside the window now, return HTCLIENT to let the controls
-                            // inside our window can still capture mouse events.
-                            *result = (isTitleBar ? HTCAPTION : HTCLIENT);
-                            return true;
+                    if (isFixedWidth || isFixedHeight) {
+                        if (isInLeftBorder && isInTopBorder) {
+                            if (isFixedWidth) {
+                                *result = HTTOP;
+                            } else {
+                                *result = HTLEFT;
+                            }
+                        } else if (isInRightBorder && isInTopBorder) {
+                            if (isFixedWidth) {
+                                *result = HTTOP;
+                            } else {
+                                *result = HTRIGHT;
+                            }
+                        } else if (isInRightBorder && isInBottomBorder) {
+                            if (isFixedWidth) {
+                                *result = HTBOTTOM;
+                            } else {
+                                *result = HTRIGHT;
+                            }
+                        } else if (isInLeftBorder && isInBottomBorder) {
+                            if (isFixedWidth) {
+                                *result = HTBOTTOM;
+                            } else {
+                                *result = HTLEFT;
+                            }
+                        } else if (isInLeftBorder || isInRightBorder) {
+                            if (isFixedWidth) {
+                                *result = HTCLIENT;
+                            } else {
+                                *result = isInLeftBorder ? HTLEFT : HTRIGHT;
+                            }
+                        } else if (isInTopBorder || isInBottomBorder) {
+                            if (isFixedHeight) {
+                                *result = HTCLIENT;
+                            } else {
+                                *result = isInTopBorder ? HTTOP : HTBOTTOM;
+                            }
+                        } else {
+                            *result = HTCLIENT;
                         }
-                        if (isTop) {
-                            if (isLeft) {
+                        return true;
+                    } else {
+                        if (isInTopBorder) {
+                            if (isInLeftBorder) {
                                 *result = HTTOPLEFT;
                                 return true;
                             }
-                            if (isRight) {
+                            if (isInRightBorder) {
                                 *result = HTTOPRIGHT;
                                 return true;
                             }
                             *result = HTTOP;
                             return true;
                         }
-                        if (isBottom) {
-                            if (isLeft) {
+                        if (isInBottomBorder) {
+                            if (isInLeftBorder) {
                                 *result = HTBOTTOMLEFT;
                                 return true;
                             }
-                            if (isRight) {
+                            if (isInRightBorder) {
                                 *result = HTBOTTOMRIGHT;
                                 return true;
                             }
                             *result = HTBOTTOM;
                             return true;
                         }
-                        if (isLeft) {
+                        if (isInLeftBorder) {
                             *result = HTLEFT;
                             return true;
                         }
-                        if (isRight) {
+                        if (isInRightBorder) {
                             *result = HTRIGHT;
                             return true;
                         }
                     }
-                    if (isTitleBar) {
+                    if (isInTitleBar) {
                         *result = HTCAPTION;
                         return true;
                     }
@@ -1919,6 +2021,17 @@
         // and align it with the upper-left corner of our new client area".
         const auto clientRect = wParam ? &(reinterpret_cast<LPNCCALCSIZE_PARAMS>(lParam))->rgrc[0]
                                        : reinterpret_cast<LPRECT>(lParam);
+        [[maybe_unused]] const auto& d3dFlickerReducer = qScopeGuard([this]() {
+            // When we receive this message, it means the window size has changed
+            // already, and it seems this message always come before any client
+            // area size notifications (eg. WM_WINDOWPOSCHANGED and WM_SIZE). Let
+            // D3D paint immediately to let user see the latest result as soon as
+            // possible.
+            if (m_windowHandle && m_windowHandle->surfaceType() == QSurface::Direct3DSurface
+                && isDwmCompositionEnabled() && DynamicApis::instance().pDwmFlush) {
+                DynamicApis::instance().pDwmFlush();
+            }
+        });
         if (isSystemBorderEnabled()) {
             // Store the original top margin before the default window procedure applies the
             // default frame.
@@ -1931,9 +2044,9 @@
             // that's also how most applications customize their title bars on Windows. It's
             // totally OK but since we want to preserve as much original frame as possible,
             // we can't use that solution.
-            const LRESULT hitTestResult = ::DefWindowProcW(hWnd, WM_NCCALCSIZE, wParam, lParam);
-            if ((hitTestResult != HTERROR) && (hitTestResult != HTNOWHERE)) {
-                *result = hitTestResult;
+            const LRESULT originalResult = ::DefWindowProcW(hWnd, WM_NCCALCSIZE, wParam, lParam);
+            if (originalResult != 0) {
+                *result = originalResult;
                 return true;
             }
             // Re-apply the original top from before the size of the default frame was
@@ -1947,7 +2060,7 @@
             clientRect->top = originalTop;
         }
 
-        const bool max = IsMaximized(hWnd);
+        const bool max = isMaximized(hWnd);
         const bool full = isFullScreen(hWnd);
         // We don't need this correction when we're fullscreen. We will
         // have the WS_POPUP size, so we don't have to worry about
@@ -2040,8 +2153,6 @@
                 }
             }
         }
-        // We should call this function only before the function returns.
-        syncPaintEventWithDwm();
         // By returning WVR_REDRAW we can make the window resizing look
         // less broken. But we must return 0 if wParam is FALSE, according to Microsoft
         // Docs.
@@ -2052,7 +2163,10 @@
         // of the upper-left non-client area. It's confirmed that this issue exists
         // from Windows 7 to Windows 10. Not tested on Windows 11 yet. Don't know
         // whether it exists on Windows XP to Windows Vista or not.
-        *result = wParam ? WVR_REDRAW : FALSE;
+
+        // https://github.com/chromium/chromium/blob/5d297da3cf2a642e9ace2b23fed097370bc70814/ui/views/win/hwnd_message_handler.cc#L2330
+        // Do not return WVR_REDRAW otherwise child HWNDs will be mispositioned.
+        *result = FALSE;
         return true;
     }
 
@@ -2062,7 +2176,7 @@
             return {GET_X_LPARAM(lParam), GET_Y_LPARAM(lParam)};
         };
         const auto getNativeGlobalPosFromKeyboard = [hWnd]() -> POINT {
-            const bool maxOrFull = IsMaximized(hWnd) || isFullScreen(hWnd);
+            const bool maxOrFull = isMaximized(hWnd) || isFullScreen(hWnd);
             const quint32 frameSize = getResizeBorderThickness(hWnd);
             const quint32 horizontalOffset =
                 ((maxOrFull || !isSystemBorderEnabled()) ? 0 : frameSize);
@@ -2094,9 +2208,12 @@
         switch (message) {
             case WM_RBUTTONUP: {
                 const POINT nativeLocalPos = getNativePosFromMouse();
-                const QPoint qtScenePos =
-                    QHighDpi::fromNativeLocalPosition(point2qpoint(nativeLocalPos), m_windowHandle);
-                if (isInTitleBarDraggableArea(qtScenePos)) {
+                const QPoint qtScenePos = QHighDpi::fromNativeLocalPosition(
+                    point2qpoint(nativeLocalPos), m_windowHandle.data());
+                WindowAgentBase::SystemButton sysButtonType = WindowAgentBase::Unknown;
+                if (isInTitleBarDraggableArea(qtScenePos) ||
+                    (isInSystemButtons(qtScenePos, &sysButtonType) &&
+                     sysButtonType == WindowAgentBase::WindowIcon)) {
                     shouldShowSystemMenu = true;
                     nativeGlobalPos = nativeLocalPos;
                     ::ClientToScreen(hWnd, &nativeGlobalPos);
@@ -2146,6 +2263,7 @@
         if (shouldShowSystemMenu) {
             static HHOOK mouseHook = nullptr;
             static std::optional<POINT> mouseClickPos;
+            static bool mouseDoubleClicked = false;
             bool mouseHookedLocal = false;
 
             // The menu is triggered by a click on icon button
@@ -2165,11 +2283,23 @@
                         WH_MOUSE,
                         [](int nCode, WPARAM wParam, LPARAM lParam) {
                             if (nCode >= 0) {
-                                if (wParam == WM_LBUTTONDOWN || wParam == WM_LBUTTONDBLCLK) {
-                                    auto pMouseStruct = reinterpret_cast<MOUSEHOOKSTRUCT *>(lParam);
-                                    if (pMouseStruct) {
-                                        mouseClickPos = pMouseStruct->pt;
+                                switch (wParam) {
+                                    case WM_LBUTTONDBLCLK:
+                                        mouseDoubleClicked = true;
+                                        Q_FALLTHROUGH();
+
+                                        // case WM_POINTERDOWN:
+
+                                    case WM_LBUTTONDOWN: {
+                                        auto pMouseStruct =
+                                            reinterpret_cast<MOUSEHOOKSTRUCT *>(lParam);
+                                        if (pMouseStruct) {
+                                            mouseClickPos = pMouseStruct->pt;
+                                        }
+                                        break;
                                     }
+                                    default:
+                                        break;
                                 }
                             }
                             return ::CallNextHookEx(nullptr, nCode, wParam, lParam);
@@ -2179,32 +2309,36 @@
                 }
             }
 
-            bool res = showSystemMenu_sys(hWnd, nativeGlobalPos, broughtByKeyboard,
-                                          m_delegate->isHostSizeFixed(m_host));
+            bool res =
+                showSystemMenu_sys(hWnd, nativeGlobalPos, broughtByKeyboard, isHostSizeFixed());
 
             // Uninstall mouse hook and check if it's a double-click
             if (mouseHookedLocal) {
                 ::UnhookWindowsHookEx(mouseHook);
 
                 // Emulate the Windows icon button's behavior
-                static uint32_t doubleClickTime = ::GetDoubleClickTime();
                 if (!res && mouseClickPos.has_value()) {
                     POINT nativeLocalPos = mouseClickPos.value();
                     ::ScreenToClient(hWnd, &nativeLocalPos);
                     QPoint qtScenePos = QHighDpi::fromNativeLocalPosition(
-                        point2qpoint(nativeLocalPos), m_windowHandle);
+                        point2qpoint(nativeLocalPos), m_windowHandle.data());
                     WindowAgentBase::SystemButton sysButtonType = WindowAgentBase::Unknown;
                     if (isInSystemButtons(qtScenePos, &sysButtonType) &&
                         sysButtonType == WindowAgentBase::WindowIcon) {
-                        iconButtonClickLevel = 1;
-                        if (::GetTickCount64() - iconButtonClickTime <= doubleClickTime) {
-                            iconButtonClickLevel = 2;
+                        iconButtonClickLevel |= IconButtonClicked;
+                        if (::GetTickCount64() - iconButtonClickTime <= ::GetDoubleClickTime()) {
+                            iconButtonClickLevel |= IconButtonTriggersClose;
                         }
                     }
                 }
 
+                if (mouseDoubleClicked) {
+                    iconButtonClickLevel |= IconButtonDoubleClicked;
+                }
+
                 mouseHook = nullptr;
                 mouseClickPos.reset();
+                mouseDoubleClicked = false;
             }
 
             // QPA's internal code will handle system menu events separately, and its

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