win: fix regression

src/core/utils_win.cpp

@@ -986,7 +986,7 @@ static constexpr const std::array<Win32Message, 333> g_win32MessageMap =
     if (it == g_win32UtilsData()->data.constEnd()) {
         return ::DefWindowProcW(hWnd, uMsg, wParam, lParam);
     }
-    // https://github.com/qt/qtbase/blob/e26a87f1ecc40bc8c6aa5b889fce67410a57a702/src/plugins/platforms/windows/qwindowscontext.cpp#L1025C10-L1025C10
+    // https://github.com/qt/qtbase/blob/e26a87f1ecc40bc8c6aa5b889fce67410a57a702/src/plugins/platforms/windows/qwindowscontext.cpp#L1025
     // We can see from the source code that Qt will filter out some messages first and then send the unfiltered
     // messages to the event dispatcher. To activate the Snap Layout feature on Windows 11, we must process
     // some non-client area messages ourself, but unfortunately these messages have been filtered out already
@@ -997,7 +997,14 @@ static constexpr const std::array<Win32Message, 333> g_win32MessageMap =
     // send it to our own custom native event filter to do all the magic works. But since the system menu feature
     // doesn't necessarily belong to the native implementation, we seperate the handling code and always process
     // the system menu part in this function for both implementations.
-    if (!usePureQtImplementation()) {
+    //
+    // https://github.com/qt/qtbase/blob/946f15efb76fffda37b77f7d194d679b904305b1/src/plugins/platforms/windows/qwindowscontext.cpp#L1541
+    // However, we can't just do this when the message is non-client area size re-calculating, because Qt QPA will
+    // do some extra work after native event filter's handling to ensure Qt windows always have correct frame margins
+    // (and correct client area size, especially when the window is maximized/fullscreen). So we still go through
+    // the normal code path of the original qWindowsWndProc() function, but only for this specific message. It should
+    // be OK because Qt won't prevent us from handling WM_NCCALCSIZE.
+    if (!usePureQtImplementation() && (uMsg != WM_NCCALCSIZE)) {
         MSG message;
         SecureZeroMemory(&message, sizeof(message));
         message.hwnd = hWnd;

src/widgets/standardtitlebar.cpp

@@ -38,6 +38,8 @@
 #include <QtGui/qpainter.h>
 #include <QtGui/qevent.h>
 #include <QtGui/qfontmetrics.h>
+#include <QtGui/qscreen.h>
+#include <QtGui/qguiapplication.h>
 #include <QtWidgets/qboxlayout.h>
 
 FRAMELESSHELPER_BEGIN_NAMESPACE
@@ -57,6 +59,42 @@ FRAMELESSHELPER_BEGIN_NAMESPACE
 
 using namespace Global;
 
+static inline void emulateLeaveEvent(QWidget *widget)
+{
+    Q_ASSERT(widget);
+    if (!widget) {
+        return;
+    }
+    QTimer::singleShot(0, widget, [widget](){
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 14, 0))
+        const QScreen *screen = widget->screen();
+#else
+        const QScreen *screen = QGuiApplication::primaryScreen();
+#endif
+        const QPoint globalPos = QCursor::pos(screen);
+        if (!QRect(widget->mapToGlobal(QPoint{ 0, 0 }), widget->size()).contains(globalPos)) {
+            QCoreApplication::postEvent(widget, new QEvent(QEvent::Leave));
+            if (widget->testAttribute(Qt::WA_Hover)) {
+                const QPoint localPos = widget->mapFromGlobal(globalPos);
+                const QPoint scenePos = widget->window()->mapFromGlobal(globalPos);
+                static constexpr const auto oldPos = QPoint{};
+                const Qt::KeyboardModifiers modifiers = QGuiApplication::keyboardModifiers();
+#if (QT_VERSION >= QT_VERSION_CHECK(6, 4, 0))
+                const auto event =  new QHoverEvent(QEvent::HoverLeave, scenePos, globalPos, oldPos, modifiers);
+                Q_UNUSED(localPos);
+#elif (QT_VERSION >= QT_VERSION_CHECK(6, 3, 0))
+                const auto event =  new QHoverEvent(QEvent::HoverLeave, localPos, globalPos, oldPos, modifiers);
+                Q_UNUSED(scenePos);
+#else
+                const auto event =  new QHoverEvent(QEvent::HoverLeave, localPos, oldPos, modifiers);
+                Q_UNUSED(scenePos);
+#endif
+                QCoreApplication::postEvent(widget, event);
+            }
+        }
+    });
+}
+
 StandardTitleBarPrivate::StandardTitleBarPrivate(StandardTitleBar *q) : QObject(q)
 {
     Q_ASSERT(q);
@@ -350,6 +388,11 @@ void StandardTitleBarPrivate::initialize()
         } else {
             window->showMaximized();
         }
+
+        // It's a Qt issue that if a QAbstractButton::clicked triggers a window's maximization,
+        // the button remains to be hovered until the mouse move. As a result, we need to
+        // manully send leave events to the button.
+        emulateLeaveEvent(maximizeButton);
     });
     closeButton = new StandardSystemButton(SystemButtonType::Close, q);
     connect(closeButton, &StandardSystemButton::clicked, this, [this](){