WindowsQPA: Make custom titlebar a child windowHEADdev

The current approach for custom titlebar uses an overlay of a
frameless popup window at the position of the titlebar area. This
involves synchronizing the window state, position and size of the
popup window with the original window. Also, the drawing of
rounded edges needs to be done manually with the old approach.
This patch adds the titlebar as a real child to the
original window, so that the window manager takes care of the
synchronization and clipping process.

Fixes: QTBUG-135643
Fixes: QTBUG-133943
Fixes: QTBUG-133946
Pick-to: 6.10 6.9
Change-Id: If23b8d9cd85b7b6abdd1e6b8b523e41e24971de3
Reviewed-by: Oliver Wolff <[email protected]>

3 files changed, 64 insertions, 157 deletions

diff --git a/src/plugins/platforms/windows/qwindowscontext.cpp b/src/plugins/platforms/windows/qwindowscontext.cpp
index 3fe837a2c03..a407cde2a7c 100644
--- a/src/plugins/platforms/windows/qwindowscontext.cpp
+++ b/src/plugins/platforms/windows/qwindowscontext.cpp
@@ -1156,9 +1156,13 @@ bool QWindowsContext::windowsProc(HWND hwnd, UINT message,
     case QtWindows::MoveEvent:
         platformWindow->handleMoved();
         return true;
-    case QtWindows::ResizeEvent:
+    case QtWindows::ResizeEvent: {
+        QWindow *window = platformWindow->window();
         platformWindow->handleResized(static_cast<int>(wParam), lParam);
+        if (window->flags().testFlags(Qt::ExpandedClientAreaHint))
+            platformWindow->updateCustomTitlebar();
         return true;
+    }
     case QtWindows::QuerySizeHints:
         platformWindow->getSizeHints(reinterpret_cast<MINMAXINFO *>(lParam));
         return true;// maybe available on some SDKs revisit WM_NCCALCSIZE
@@ -1174,8 +1178,12 @@ bool QWindowsContext::windowsProc(HWND hwnd, UINT message,
         return platformWindow->handleNonClientActivate(result);
     case QtWindows::GeometryChangingEvent:
         return platformWindow->handleGeometryChanging(&msg);
-    case QtWindows::ExposeEvent:
+    case QtWindows::ExposeEvent: {
+        QWindow *window = platformWindow->window();
+        if (window->flags().testFlags(Qt::ExpandedClientAreaHint))
+            platformWindow->updateCustomTitlebar();
         return platformWindow->handleWmPaint(hwnd, message, wParam, lParam, result);
+    }
     case QtWindows::NonClientMouseEvent:
         if (!platformWindow->frameStrutEventsEnabled())
             break;
diff --git a/src/plugins/platforms/windows/qwindowswindow.cpp b/src/plugins/platforms/windows/qwindowswindow.cpp
index a4bb59cf42c..731673b61db 100644
--- a/src/plugins/platforms/windows/qwindowswindow.cpp
+++ b/src/plugins/platforms/windows/qwindowswindow.cpp
@@ -284,40 +284,6 @@ static inline RECT RECTfromQRect(const QRect &rect)
     return result;
 }
 
-static LRESULT WINAPI WndProcTitleBar(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
-{
-    HWND parentHwnd = reinterpret_cast<HWND>(GetWindowLongPtr(hwnd, GWL_HWNDPARENT));
-    QWindowsWindow* platformWindow = QWindowsContext::instance()->findPlatformWindow(parentHwnd);
-
-    switch (message) {
-    case WM_SHOWWINDOW:
-        ShowWindow(hwnd,SW_HIDE);
-        if ((BOOL)wParam == TRUE)
-            platformWindow->transitionAnimatedCustomTitleBar();
-        return 0;
-    case WM_SIZE: {
-        if (platformWindow)
-            platformWindow->updateCustomTitlebar();
-        break;
-    }
-    case WM_NCHITTEST:
-        return HTTRANSPARENT;
-    case WM_TIMER:
-        ShowWindow(hwnd, SW_SHOWNOACTIVATE);
-        platformWindow->updateCustomTitlebar();
-        break;
-    case WM_PAINT:
-    {
-        PAINTSTRUCT ps;
-        BeginPaint(hwnd, &ps);
-        EndPaint(hwnd, &ps);
-        return 0;
-    }
-    }
-    return DefWindowProc(hwnd, message, wParam, lParam);
-}
-
-
 #ifndef QT_NO_DEBUG_STREAM
 QDebug operator<<(QDebug d, const RECT &r)
 {
@@ -917,7 +883,7 @@ QWindowsWindowData
     const auto appinst = reinterpret_cast<HINSTANCE>(GetModuleHandle(nullptr));
 
     const QString windowClassName = QWindowsContext::instance()->registerWindowClass(w);
-    const QString windowTitlebarName = QWindowsContext::instance()->registerWindowClass(QStringLiteral("_q_titlebar"), WndProcTitleBar, CS_VREDRAW|CS_HREDRAW, nullptr, false);
+    const QString windowTitlebarName = QWindowsContext::instance()->registerWindowClass(QStringLiteral("_q_titlebar"), DefWindowProc, CS_VREDRAW|CS_HREDRAW, nullptr, false);
 
     const QScreen *screen{};
     const QRect rect = QPlatformWindow::initialGeometry(w, data.geometry,
@@ -970,15 +936,13 @@ QWindowsWindowData
                                  context->frameWidth, context->frameHeight,
                                  parentHandle, nullptr, appinst, nullptr);
 
-    if (w->flags().testFlags(Qt::ExpandedClientAreaHint)) {
-        const UINT dpi = ::GetDpiForWindow(result.hwnd);
-        const int titleBarHeight = getTitleBarHeight_sys(dpi);
-        result.hwndTitlebar = CreateWindowEx(WS_EX_LAYERED | WS_EX_TRANSPARENT,
-                                             classTitleBarNameUtf16, classTitleBarNameUtf16,
-                                             WS_POPUP, 0, 0,
-                                             context->frameWidth, titleBarHeight,
-                                             result.hwnd, nullptr, appinst, nullptr);
-    }
+    const UINT dpi = ::GetDpiForWindow(result.hwnd);
+    const int titleBarHeight = getTitleBarHeight_sys(dpi);
+    result.hwndTitlebar = CreateWindowEx(WS_EX_LAYERED | WS_EX_TRANSPARENT | WS_EX_NOACTIVATE,
+                                         classTitleBarNameUtf16, classTitleBarNameUtf16,
+                                         0, 0, 0,
+                                         context->frameWidth, titleBarHeight,
+                                         nullptr, nullptr, appinst, nullptr);
 
     qCDebug(lcQpaWindow).nospace()
         << "CreateWindowEx: returns " << w << ' ' << result.hwnd << " obtained geometry: "
@@ -1056,6 +1020,9 @@ void WindowCreationData::initialize(const QWindow *w, HWND hwnd, bool frameChang
         if (flags & Qt::ExpandedClientAreaHint) { // Gives us the rounded corners looks and the frame shadow
             MARGINS margins = { -1, -1, -1, -1 };
             DwmExtendFrameIntoClientArea(hwnd, &margins);
+        } else {
+            MARGINS margins = { 0, 0, 0, 0 };
+            DwmExtendFrameIntoClientArea(hwnd, &margins);
         }
     } else { // child.
         SetWindowPos(hwnd, HWND_TOP, 0, 0, 0, 0, swpFlags);
@@ -1196,19 +1163,21 @@ bool QWindowsGeometryHint::handleCalculateSize(const QWindow *window, const QMar
         *result = 0;
         return true;
     }
+    const QWindowsWindow *platformWindow = QWindowsWindow::windowsWindowOf(window);
+    // In case the platformwindow was not yet created, use the initial windowflags provided by the user.
+    const bool clientAreaExpanded = platformWindow != nullptr ? platformWindow->isClientAreaExpanded() : window->flags() & Qt::ExpandedClientAreaHint;
     // Return 0 to remove the window's border
-    const bool clientAreaExpanded = window->flags() & Qt::ExpandedClientAreaHint;
     if (msg.wParam && clientAreaExpanded) {
         // Prevent content from being cutoff by border for maximized, but not fullscreened windows.
-        if (IsZoomed(msg.hwnd) && window->visibility() != QWindow::FullScreen) {
-            auto *ncp = reinterpret_cast<NCCALCSIZE_PARAMS *>(msg.lParam);
-            RECT *clientArea = &ncp->rgrc[0];
-            const int border = getResizeBorderThickness(QWindowsWindow::windowsWindowOf(window)->savedDpi());
+        const bool maximized = IsZoomed(msg.hwnd) && window->visibility() != QWindow::FullScreen;
+        auto *ncp = reinterpret_cast<NCCALCSIZE_PARAMS *>(msg.lParam);
+        RECT *clientArea = &ncp->rgrc[0];
+        const int border = getResizeBorderThickness(96);
+        if (maximized)
             clientArea->top += border;
-            clientArea->bottom -= border;
-            clientArea->left += border;
-            clientArea->right -= border;
-        }
+        clientArea->bottom -= border;
+        clientArea->left += border;
+        clientArea->right -= border;
         *result = 0;
         return true;
     }
@@ -1628,6 +1597,12 @@ QWindowsWindow::QWindowsWindow(QWindow *aWindow, const QWindowsWindowData &data)
 #endif
 {
     QWindowsContext::instance()->addWindow(m_data.hwnd, this);
+
+    if (aWindow->flags().testFlags(Qt::ExpandedClientAreaHint)) {
+        SetParent(m_data.hwndTitlebar, m_data.hwnd);
+        ShowWindow(m_data.hwndTitlebar, SW_SHOW);
+    }
+
     const Qt::WindowType type = aWindow->type();
     if (type == Qt::Desktop)
         return; // No further handling for Qt::Desktop
@@ -1852,21 +1827,6 @@ QWindow *QWindowsWindow::topLevelOf(QWindow *w)
     return w;
 }
 
-// Checks whether the Window is tiled with Aero snap
-bool QWindowsWindow::isWindowArranged(HWND hwnd)
-{
-    typedef BOOL(WINAPI* PIsWindowArranged)(HWND);
-    static PIsWindowArranged pIsWindowArranged = nullptr;
-    static bool resolved = false;
-    if (!resolved) {
-        resolved = true;
-        pIsWindowArranged = (PIsWindowArranged)QSystemLibrary::resolve(QLatin1String("user32.dll"), "IsWindowArranged");
-    }
-    if (pIsWindowArranged == nullptr)
-        return false;
-    return pIsWindowArranged(hwnd);
-}
-
 QWindowsWindowData
     QWindowsWindowData::create(const QWindow *w,
                                        const QWindowsWindowData &parameters,
@@ -1908,13 +1868,6 @@ void QWindowsWindow::setVisible(bool visible)
             fireExpose(QRegion());
         }
     }
-    if (m_data.hwndTitlebar) {
-        if (visible) {
-            SetWindowPos(m_data.hwndTitlebar, HWND_TOP, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE | SWP_NOACTIVATE);
-        } else {
-            ShowWindow(m_data.hwndTitlebar, SW_HIDE);
-        }
-    }
 }
 
 bool QWindowsWindow::isVisible() const
@@ -2055,10 +2008,6 @@ void QWindowsWindow::show_sys() const
         setFlag(WithinMaximize); // QTBUG-8361
 
     ShowWindow(m_data.hwnd, sm);
-    if (m_data.flags.testFlag(Qt::ExpandedClientAreaHint)) {
-        ShowWindow(m_data.hwndTitlebar, sm);
-        SetActiveWindow(m_data.hwnd);
-    }
 
     clearFlag(WithinMaximize);
 
@@ -2250,7 +2199,7 @@ QRect QWindowsWindow::normalGeometry() const
 QMargins QWindowsWindow::safeAreaMargins() const
 {
     if (m_data.flags.testFlags(Qt::ExpandedClientAreaHint)) {
-        const int titleBarHeight = getTitleBarHeight_sys(savedDpi());
+        const int titleBarHeight = getTitleBarHeight_sys(96);
 
         return QMargins(0, titleBarHeight, 0, 0);
     }
@@ -2462,15 +2411,9 @@ void QWindowsWindow::handleGeometryChange()
         clearFlag(SynchronousGeometryChangeEvent);
     qCDebug(lcQpaEvents) << __FUNCTION__ << this << window() << m_data.geometry;
 
-    if (m_data.hwndTitlebar) {
-        bool arranged = QWindowsWindow::isWindowArranged(m_data.hwnd);
-        if (arranged || (m_windowWasArranged && !arranged))
-            transitionAnimatedCustomTitleBar();
-
+    if (m_data.flags & Qt::ExpandedClientAreaHint) {
         const int titleBarHeight = getTitleBarHeight_sys(savedDpi());
-        MoveWindow(m_data.hwndTitlebar, m_data.geometry.x(), m_data.geometry.y(),
-                   m_data.geometry.width(), titleBarHeight, true);
-        m_windowWasArranged = arranged;
+        MoveWindow(m_data.hwndTitlebar, 0, 0, m_data.geometry.width(), titleBarHeight, true);
     }
 }
 
@@ -2632,6 +2575,16 @@ QWindowsWindowData QWindowsWindow::setWindowFlags_sys(Qt::WindowFlags wt,
     creationData.applyWindowFlags(m_data.hwnd);
     creationData.initialize(window(), m_data.hwnd, true, m_opacity);
 
+    if (creationData.flags.testFlag(Qt::ExpandedClientAreaHint)) {
+        SetParent(m_data.hwndTitlebar, m_data.hwnd);
+        ShowWindow(m_data.hwndTitlebar, SW_SHOW);
+    } else {
+        if (IsWindowVisible(m_data.hwndTitlebar)) {
+            SetParent(m_data.hwndTitlebar, HWND_MESSAGE);
+            ShowWindow(m_data.hwndTitlebar, SW_HIDE);
+        }
+    }
+
     QWindowsWindowData result = m_data;
     result.flags = creationData.flags;
     result.embedded = creationData.embedded;
@@ -2650,7 +2603,7 @@ void QWindowsWindow::handleWindowStateChange(Qt::WindowStates state)
         handleHidden();
         QWindowSystemInterface::flushWindowSystemEvents(QEventLoop::ExcludeUserInputEvents); // Tell QQuickWindow to stop rendering now.
     } else {
-        transitionAnimatedCustomTitleBar();
+        updateCustomTitlebar();
         if (state & Qt::WindowMaximized) {
             WINDOWPLACEMENT windowPlacement{};
             windowPlacement.length = sizeof(WINDOWPLACEMENT);
@@ -2748,20 +2701,6 @@ void QWindowsWindow::correctWindowPlacement(WINDOWPLACEMENT &windowPlacement)
     }
 }
 
-void QWindowsWindow::transitionAnimatedCustomTitleBar()
-{
-    if (!m_data.hwndTitlebar)
-        return;
-    const QWinRegistryKey registry(HKEY_CURRENT_USER, LR"(Control Panel\Desktop\WindowMetrics)");
-    if (registry.isValid() && registry.value(LR"(MinAnimate)") == 1) {
-        ShowWindow(m_data.hwndTitlebar, SW_HIDE);
-        SetTimer(m_data.hwndTitlebar, 1, 200, nullptr);
-    } else {
-        ShowWindow(m_data.hwndTitlebar, SW_SHOWNOACTIVATE);
-        updateCustomTitlebar();
-    }
-}
-
 void QWindowsWindow::updateRestoreGeometry()
 {
     m_data.restoreGeometry = normalFrameGeometry(m_data.hwnd);
@@ -3083,7 +3022,8 @@ void QWindowsWindow::calculateFullFrameMargins()
     const auto systemMargins = testFlag(DisableNonClientScaling)
         ? QWindowsGeometryHint::frameOnPrimaryScreen(window(), m_data.hwnd)
         : frameMargins_sys();
-    const QMargins actualMargins = systemMargins + customMargins();
+    const int extendedClientAreaBorder = window()->flags().testFlag(Qt::ExpandedClientAreaHint) ? qRound(QHighDpiScaling::factor(window())) * 2 : 0;
+    const QMargins actualMargins = systemMargins + customMargins() - extendedClientAreaBorder;
 
     const int yDiff = (windowRect.bottom - windowRect.top) - (clientRect.bottom - clientRect.top);
     const bool typicalFrame = (actualMargins.left() == actualMargins.right())
@@ -3522,19 +3462,6 @@ bool QWindowsWindow::handleNonClientActivate(LRESULT *result) const
     return false;
 }
 
-static void _q_drawCustomTitleBarButton(QPainter& p, const QRectF& r)
-{
-    QPainterPath path(QPointF(r.x(), r.y()));
-    QRectF rightCorner(r.x() + r.width() - 2.0, r.y() + 4.0, 2, 2);
-    QRectF leftCorner(r.x(), r.y() + 4, 2, 2);
-    path.lineTo(r.x() + r.width() - 5.0f, r.y());
-    path.arcTo(rightCorner, 90, -90);
-    path.lineTo(r.x() + r.width(), r.y() + r.height() - 1);
-    path.lineTo(r.x(), r.y() + r.height() - 1);
-    path.closeSubpath();
-    p.drawPath(path);
-}
-
 void QWindowsWindow::updateCustomTitlebar()
 {
     HWND hwnd = m_data.hwndTitlebar;
@@ -3550,7 +3477,7 @@ void QWindowsWindow::updateCustomTitlebar()
 
     POINT localPos;
     GetCursorPos(&localPos);
-    MapWindowPoints(HWND_DESKTOP, hwnd, &localPos, 1);
+    MapWindowPoints(HWND_DESKTOP, m_data.hwnd, &localPos, 1);
 
     const bool isDarkmode = QWindowsIntegration::instance()->darkModeHandling().testFlags(QWindowsApplication::DarkModeWindowFrames) &&
             qApp->styleHints()->colorScheme() == Qt::ColorScheme::Dark;
@@ -3572,25 +3499,9 @@ void QWindowsWindow::updateCustomTitlebar()
     p.setPen(Qt::NoPen);
     if (!wnd->flags().testFlags(Qt::NoTitleBarBackgroundHint)) {
         QRect titleRect;
-        titleRect.setX(2);
         titleRect.setWidth(windowWidth);
         titleRect.setHeight(titleBarHeight);
-
-        if (isWindows11orAbove) {
-            QPainterPath path(QPointF(titleRect.x() + 4.0f, titleRect.y()));
-            QRectF rightCorner(titleRect.x() + titleRect.width() - 4.0, titleRect.y() + 4.0, 2, 2);
-            QRectF leftCorner(titleRect.x(), titleRect.y() + 4, 2, 2);
-            path.lineTo(titleRect.x() + titleRect.width() - 7.0f, titleRect.y());
-            path.arcTo(rightCorner, 90, -90);
-            path.lineTo(titleRect.x() + titleRect.width() - 2.0, titleRect.y() + titleRect.height() - 1);
-            path.lineTo(titleRect.x(), titleRect.y() + titleRect.height() - 1);
-            path.lineTo(titleRect.x(), titleRect.y() + 4.0f);
-            path.arcTo(leftCorner, -90, -90);
-            path.closeSubpath();
-            p.drawPath(path);
-        } else {
-            p.drawRect(titleRect);
-        }
+        p.drawRect(titleRect);
     }
 
     if (wnd->flags().testFlags(Qt::WindowTitleHint | Qt::CustomizeWindowHint) || !wnd->flags().testFlag(Qt::CustomizeWindowHint)) {
@@ -3636,15 +3547,12 @@ void QWindowsWindow::updateCustomTitlebar()
         QRectF rect;
         rect.setY(1);
         rect.setX(windowWidth - titleButtonWidth * buttons);
-        rect.setWidth(titleButtonWidth - 1);
+        rect.setWidth(titleButtonWidth);
         rect.setHeight(titleBarHeight);
         if (localPos.x > (windowWidth - buttons * titleButtonWidth) &&
             localPos.x < (windowWidth - (buttons - 1) * titleButtonWidth) &&
             localPos.y > rect.y() && localPos.y < rect.y() + rect.height()) {
-            if (isWindows11orAbove && buttons == 1)
-                _q_drawCustomTitleBarButton(p, rect);
-            else
-                p.drawRect(rect);
+            p.drawRect(rect);
             const QPen closeButtonHoveredPen = QPen(QColor(0xFF, 0xFF, 0xFD, 0xFF));
             p.setPen(closeButtonHoveredPen);
         } else {
@@ -3660,15 +3568,12 @@ void QWindowsWindow::updateCustomTitlebar()
         QRectF rect;
         rect.setY(1);
         rect.setX(windowWidth - titleButtonWidth * buttons);
-        rect.setWidth(titleButtonWidth - 1);
+        rect.setWidth(titleButtonWidth);
         rect.setHeight(titleBarHeight);
         if (localPos.x > (windowWidth - buttons * titleButtonWidth) &&
             localPos.x < (windowWidth - (buttons - 1) * titleButtonWidth) &&
             localPos.y > rect.y() && localPos.y < rect.y() + rect.height()) {
-            if (isWindows11orAbove && buttons == 1)
-                _q_drawCustomTitleBarButton(p, rect);
-            else
-                p.drawRect(rect);
+            p.drawRect(rect);
         }
         p.setPen(textPen);
         p.drawText(rect,QStringLiteral("\uE922"), QTextOption(Qt::AlignVCenter | Qt::AlignHCenter));
@@ -3681,15 +3586,12 @@ void QWindowsWindow::updateCustomTitlebar()
         QRectF rect;
         rect.setY(1);
         rect.setX(windowWidth - titleButtonWidth * buttons);
-        rect.setWidth(titleButtonWidth - 1);
+        rect.setWidth(titleButtonWidth);
         rect.setHeight(titleBarHeight);
         if (localPos.x > (windowWidth - buttons * titleButtonWidth) &&
             localPos.x < (windowWidth - (buttons - 1) * titleButtonWidth) &&
             localPos.y > rect.y() && localPos.y < rect.y() + rect.height()) {
-            if (isWindows11orAbove && buttons == 1)
-                _q_drawCustomTitleBarButton(p, rect);
-            else
-                p.drawRect(rect);
+            p.drawRect(rect);
         }
         p.setPen(textPen);
         p.drawText(rect,QStringLiteral("\uE921"), QTextOption(Qt::AlignVCenter | Qt::AlignHCenter));
@@ -3707,7 +3609,7 @@ void QWindowsWindow::updateCustomTitlebar()
 
 
     BLENDFUNCTION blend = {AC_SRC_OVER, 0, 255, AC_SRC_ALPHA};
-    POINT ptLocation = { windowRect.left, windowRect.top };
+    POINT ptLocation = { 0, 0 };
     SIZE szWnd = { windowWidth, titleBarHeight };
     POINT ptSrc = { 0, 0 };
     UpdateLayeredWindow(hwnd, hdc, &ptLocation, &szWnd, memdc, &ptSrc, 0, &blend, ULW_ALPHA);
diff --git a/src/plugins/platforms/windows/qwindowswindow.h b/src/plugins/platforms/windows/qwindowswindow.h
index b67bd2850b3..a0e150aeb01 100644
--- a/src/plugins/platforms/windows/qwindowswindow.h
+++ b/src/plugins/platforms/windows/qwindowswindow.h
@@ -307,7 +307,6 @@ public:
     static QWindow *topLevelOf(QWindow *w);
     static inline void *userDataOf(HWND hwnd);
     static inline void setUserDataOf(HWND hwnd, void *ud);
-    static bool isWindowArranged(HWND hwnd);
 
     static bool hasNoNativeFrame(HWND hwnd, Qt::WindowFlags flags);
     static bool setWindowLayered(HWND hwnd, Qt::WindowFlags flags, bool hasAlpha, qreal opacity);
@@ -359,12 +358,10 @@ public:
     int savedDpi() const { return m_savedDpi; }
     qreal dpiRelativeScale(const UINT dpi) const;
 
-    bool isFrameless() const { return m_data.flags.testFlag(Qt::FramelessWindowHint); }
+    bool isClientAreaExpanded() const { return m_data.flags.testFlag(Qt::ExpandedClientAreaHint); }
 
     void requestUpdate() override;
 
-    void transitionAnimatedCustomTitleBar();
-
 private:
     inline void show_sys() const;
     inline QWindowsWindowData setWindowFlags_sys(Qt::WindowFlags wt, unsigned flags = 0) const;