Windows QPA: Fix RTL window title bars

Add a platform option to the plugin (-platform windows:reverse) that
enables reverse mode. It sets WS_EX_LAYOUTRTL on RTL windows, forces normal
orientation on all HDCs created for the window, fixes
ClientToScreen()/ScreenToClient() accordingly and transforms mouse events.

[ChangeLog][Platform Specific Changes][Windows] It is now possible
to enable RTL mode by passing the option -platform windows:reverse.

Fixes: QTBUG-28463
Change-Id: I4d70818b2fd315d4e8d5627eab11ae912c6e77be
Reviewed-by: Miikka Heikkinen <miikka.heikkinen@qt.io>
Reviewed-by: André de la Rocha <andre.rocha@qt.io>
 
 
 
 

7 files changed, 110 insertions, 23 deletions

diff --git a/src/plugins/platforms/windows/qwindowscontext.cpp b/src/plugins/platforms/windows/qwindowscontext.cpp
index 320b5b1a41..f93d196b20 100644
--- a/src/plugins/platforms/windows/qwindowscontext.cpp
+++ b/src/plugins/platforms/windows/qwindowscontext.cpp
@@ -713,7 +713,7 @@ static inline bool findPlatformWindowHelper(const POINT &screenPoint, unsigned c
                                             HWND *hwnd, QWindowsWindow **result)
 {
     POINT point = screenPoint;
-    ScreenToClient(*hwnd, &point);
+    screenToClient(*hwnd, &point);
     // Returns parent if inside & none matched.
     const HWND child = ChildWindowFromPointEx(*hwnd, point, cwexFlags);
     if (!child || child == *hwnd)
@@ -1043,7 +1043,7 @@ bool QWindowsContext::windowsProc(HWND hwnd, UINT message,
         // For non-client-area messages, these are screen coordinates (as expected
         // in the MSG structure), otherwise they are client coordinates.
         if (!(et & QtWindows::NonClientEventFlag)) {
-            ClientToScreen(msg.hwnd, &msg.pt);
+            clientToScreen(msg.hwnd, &msg.pt);
         }
     } else {
         GetCursorPos(&msg.pt);
@@ -1134,13 +1134,11 @@ bool QWindowsContext::windowsProc(HWND hwnd, UINT message,
         case QtWindows::QuerySizeHints:
             d->m_creationContext->applyToMinMaxInfo(reinterpret_cast<MINMAXINFO *>(lParam));
             return true;
-        case QtWindows::ResizeEvent: {
-            const QSize size(GET_X_LPARAM(lParam), GET_Y_LPARAM(lParam) - d->m_creationContext->menuHeight);
-            d->m_creationContext->obtainedGeometry.setSize(size);
-        }
+        case QtWindows::ResizeEvent:
+            d->m_creationContext->obtainedSize = QSize(GET_X_LPARAM(lParam), GET_Y_LPARAM(lParam));
             return true;
         case QtWindows::MoveEvent:
-            d->m_creationContext->obtainedGeometry.moveTo(GET_X_LPARAM(lParam), GET_Y_LPARAM(lParam));
+            d->m_creationContext->obtainedPos = QPoint(GET_X_LPARAM(lParam), GET_Y_LPARAM(lParam));
             return true;
         case QtWindows::NonClientCreate:
             if (shouldHaveNonClientDpiScaling(d->m_creationContext->window))
diff --git a/src/plugins/platforms/windows/qwindowsintegration.cpp b/src/plugins/platforms/windows/qwindowsintegration.cpp
index 4e319c2326..8dd3810463 100644
--- a/src/plugins/platforms/windows/qwindowsintegration.cpp
+++ b/src/plugins/platforms/windows/qwindowsintegration.cpp
@@ -217,6 +217,8 @@ static inline unsigned parseOptions(const QStringList &paramList,
             options |= QWindowsIntegration::NoNativeMenus;
         } else if (param == QLatin1String("nowmpointer")) {
             options |= QWindowsIntegration::DontUseWMPointer;
+        } else if (param == QLatin1String("reverse")) {
+            options |= QWindowsIntegration::RtlEnabled;
         } else {
             qWarning() << "Unknown option" << param;
         }
diff --git a/src/plugins/platforms/windows/qwindowsintegration.h b/src/plugins/platforms/windows/qwindowsintegration.h
index e28b2c2fb3..015cf79b6c 100644
--- a/src/plugins/platforms/windows/qwindowsintegration.h
+++ b/src/plugins/platforms/windows/qwindowsintegration.h
@@ -69,7 +69,8 @@ public:
         AlwaysUseNativeMenus = 0x100,
         NoNativeMenus = 0x200,
         DontUseWMPointer = 0x400,
-        DetectAltGrModifier = 0x800
+        DetectAltGrModifier = 0x800,
+        RtlEnabled = 0x1000
     };
 
     explicit QWindowsIntegration(const QStringList &paramList);
diff --git a/src/plugins/platforms/windows/qwindowsmousehandler.cpp b/src/plugins/platforms/windows/qwindowsmousehandler.cpp
index c4d53855a5..5a52cd3ea8 100644
--- a/src/plugins/platforms/windows/qwindowsmousehandler.cpp
+++ b/src/plugins/platforms/windows/qwindowsmousehandler.cpp
@@ -106,7 +106,7 @@ static inline void compressMouseMove(MSG *msg)
                 // Extract the x,y coordinates from the lParam as we do in the WndProc
                 msg->pt.x = GET_X_LPARAM(mouseMsg.lParam);
                 msg->pt.y = GET_Y_LPARAM(mouseMsg.lParam);
-                ClientToScreen(msg->hwnd, &(msg->pt));
+                clientToScreen(msg->hwnd, &(msg->pt));
                 // Remove the mouse move message
                 PeekMessage(&mouseMsg, msg->hwnd, WM_MOUSEMOVE,
                             WM_MOUSEMOVE, PM_REMOVE);
@@ -262,7 +262,13 @@ bool QWindowsMouseHandler::translateMouseEvent(QWindow *window, HWND hwnd,
     if (et == QtWindows::MouseWheelEvent)
         return translateMouseWheelEvent(window, hwnd, msg, result);
 
-    const QPoint winEventPosition(GET_X_LPARAM(msg.lParam), GET_Y_LPARAM(msg.lParam));
+    QPoint winEventPosition(GET_X_LPARAM(msg.lParam), GET_Y_LPARAM(msg.lParam));
+    if ((et & QtWindows::NonClientEventFlag) == 0 && QWindowsBaseWindow::isRtlLayout(hwnd))  {
+        RECT clientArea;
+        GetClientRect(hwnd, &clientArea);
+        winEventPosition.setX(clientArea.right - winEventPosition.x());
+    }
+
     QPoint clientPosition;
     QPoint globalPosition;
     if (et & QtWindows::NonClientEventFlag) {
diff --git a/src/plugins/platforms/windows/qwindowspointerhandler.cpp b/src/plugins/platforms/windows/qwindowspointerhandler.cpp
index b730dbcf3b..0e686bfb10 100644
--- a/src/plugins/platforms/windows/qwindowspointerhandler.cpp
+++ b/src/plugins/platforms/windows/qwindowspointerhandler.cpp
@@ -688,7 +688,13 @@ bool QWindowsPointerHandler::translateMouseEvent(QWindow *window,
 {
     *result = 0;
 
-    const QPoint eventPos(GET_X_LPARAM(msg.lParam), GET_Y_LPARAM(msg.lParam));
+    QPoint eventPos(GET_X_LPARAM(msg.lParam), GET_Y_LPARAM(msg.lParam));
+    if ((et & QtWindows::NonClientEventFlag) == 0 && QWindowsBaseWindow::isRtlLayout(hwnd))  {
+        RECT clientArea;
+        GetClientRect(hwnd, &clientArea);
+        eventPos.setX(clientArea.right - eventPos.x());
+    }
+
     QPoint localPos;
     QPoint globalPos;
 
diff --git a/src/plugins/platforms/windows/qwindowswindow.cpp b/src/plugins/platforms/windows/qwindowswindow.cpp
index d8273194fa..e700e6cff4 100644
--- a/src/plugins/platforms/windows/qwindowswindow.cpp
+++ b/src/plugins/platforms/windows/qwindowswindow.cpp
@@ -134,6 +134,10 @@ static QByteArray debugWinExStyle(DWORD exStyle)
         rc += " WS_EX_LAYERED";
     if (exStyle & WS_EX_DLGMODALFRAME)
         rc += " WS_EX_DLGMODALFRAME";
+    if (exStyle & WS_EX_LAYOUTRTL)
+        rc += " WS_EX_LAYOUTRTL";
+    if (exStyle & WS_EX_NOINHERITLAYOUT)
+        rc += " WS_EX_NOINHERITLAYOUT";
     return rc;
 }
 
@@ -307,7 +311,7 @@ static inline QRect frameGeometry(HWND hwnd, bool topLevel)
         const int width = rect.right - rect.left;
         const int height = rect.bottom - rect.top;
         POINT leftTop = { rect.left, rect.top };
-        ScreenToClient(parent, &leftTop);
+        screenToClient(parent, &leftTop);
         rect.left = leftTop.x;
         rect.top = leftTop.y;
         rect.right = leftTop.x + width;
@@ -667,6 +671,17 @@ void WindowCreationData::fromWindow(const QWindow *w, const Qt::WindowFlags flag
     if ((flags & Qt::MSWindowsFixedSizeDialogHint))
         dialog = true;
 
+    // This causes the title bar to drawn RTL and the close button
+    // to be left. Note that this causes:
+    // - All DCs created on the Window to have RTL layout (see SetLayout)
+    // - ClientToScreen() and ScreenToClient() to work in reverse as well.
+    // - Mouse event coordinates to be mirrored.
+    // - Positioning of child Windows.
+    if (QGuiApplication::layoutDirection() == Qt::RightToLeft
+        && (QWindowsIntegration::instance()->options() & QWindowsIntegration::RtlEnabled) != 0) {
+        exStyle |= WS_EX_LAYOUTRTL | WS_EX_NOINHERITLAYOUT;
+    }
+
     // Parent: Use transient parent for top levels.
     if (popup) {
         flags |= Qt::WindowStaysOnTopHint; // a popup stays on top, no parent.
@@ -772,6 +787,16 @@ QWindowsWindowData
 
     QPoint pos = calcPosition(w, context, invMargins);
 
+    // Mirror the position when creating on a parent in RTL mode, ditto for the obtained geometry.
+    int mirrorParentWidth = 0;
+    if (!w->isTopLevel() && QWindowsBaseWindow::isRtlLayout(parentHandle)) {
+        RECT rect;
+        GetClientRect(parentHandle, &rect);
+        mirrorParentWidth = rect.right;
+    }
+    if (mirrorParentWidth != 0 && pos.x() != CW_USEDEFAULT && context->frameWidth != CW_USEDEFAULT)
+        pos.setX(mirrorParentWidth - context->frameWidth - pos.x());
+
     result.hwnd = CreateWindowEx(exStyle, classNameUtf16, titleUtf16,
                                  style,
                                  pos.x(), pos.y(),
@@ -779,14 +804,21 @@ QWindowsWindowData
                                  parentHandle, nullptr, appinst, nullptr);
     qCDebug(lcQpaWindows).nospace()
         << "CreateWindowEx: returns " << w << ' ' << result.hwnd << " obtained geometry: "
-        << context->obtainedGeometry << ' ' << context->margins;
+        << context->obtainedPos << context->obtainedSize << ' ' << context->margins;
 
     if (!result.hwnd) {
         qErrnoWarning("%s: CreateWindowEx failed", __FUNCTION__);
         return result;
     }
 
-    result.geometry = context->obtainedGeometry;
+    if (mirrorParentWidth != 0) {
+        context->obtainedPos.setX(mirrorParentWidth - context->obtainedSize.width()
+                                  -  context->obtainedPos.x());
+    }
+
+    QRect obtainedGeometry(context->obtainedPos, context->obtainedSize);
+
+    result.geometry = obtainedGeometry;
     result.fullFrameMargins = context->margins;
     result.embedded = embedded;
     result.hasFrame = hasFrame;
@@ -1031,6 +1063,11 @@ bool QWindowsGeometryHint::positionIncludesFrame(const QWindow *w)
     \ingroup qt-lighthouse-win
 */
 
+bool QWindowsBaseWindow::isRtlLayout(HWND hwnd)
+{
+    return (GetWindowLongPtrW(hwnd, GWL_EXSTYLE) & WS_EX_LAYOUTRTL) != 0;
+}
+
 QWindowsBaseWindow *QWindowsBaseWindow::baseWindowOf(const QWindow *w)
 {
     if (w) {
@@ -1193,7 +1230,9 @@ QWindowCreationContext::QWindowCreationContext(const QWindow *w,
                                                DWORD style, DWORD exStyle) :
     window(w),
     requestedGeometryIn(geometryIn),
-    requestedGeometry(geometry), obtainedGeometry(geometry),
+    requestedGeometry(geometry),
+    obtainedPos(geometryIn.topLeft()),
+    obtainedSize(geometryIn.size()),
     margins(QWindowsGeometryHint::frame(w, geometry, style, exStyle)),
     customMargins(cm)
 {
@@ -1321,11 +1360,12 @@ void QWindowsWindow::initialize()
     // will send the message) and screen change signals of QWindow.
     if (w->type() != Qt::Desktop) {
         const Qt::WindowState state = w->windowState();
+        const QRect obtainedGeometry(creationContext->obtainedPos, creationContext->obtainedSize);
         if (state != Qt::WindowMaximized && state != Qt::WindowFullScreen
-            && creationContext->requestedGeometryIn != creationContext->obtainedGeometry) {
-            QWindowSystemInterface::handleGeometryChange<QWindowSystemInterface::SynchronousDelivery>(w, creationContext->obtainedGeometry);
+            && creationContext->requestedGeometryIn != obtainedGeometry) {
+            QWindowSystemInterface::handleGeometryChange<QWindowSystemInterface::SynchronousDelivery>(w, obtainedGeometry);
         }
-        QPlatformScreen *obtainedScreen = screenForGeometry(creationContext->obtainedGeometry);
+        QPlatformScreen *obtainedScreen = screenForGeometry(obtainedGeometry);
         if (obtainedScreen && screen() != obtainedScreen)
             QWindowSystemInterface::handleWindowScreenChanged<QWindowSystemInterface::SynchronousDelivery>(w, obtainedScreen->screen());
     }
@@ -1942,7 +1982,16 @@ void QWindowsBaseWindow::setGeometry_sys(const QRect &rect) const
         windowPlacement.showCmd = windowPlacement.showCmd == SW_SHOWMINIMIZED ? SW_SHOWMINIMIZED : SW_HIDE;
         result = SetWindowPlacement(hwnd, &windowPlacement);
     } else {
-        result = MoveWindow(hwnd, frameGeometry.x(), frameGeometry.y(),
+        int x = frameGeometry.x();
+        if (!window()->isTopLevel()) {
+            const HWND parentHandle = GetParent(hwnd);
+            if (isRtlLayout(parentHandle)) {
+                RECT rect;
+                GetClientRect(parentHandle, &rect);
+                x = rect.right - frameGeometry.width() - x;
+            }
+        }
+        result = MoveWindow(hwnd, x, frameGeometry.y(),
                             frameGeometry.width(), frameGeometry.height(), true);
     }
     qCDebug(lcQpaWindows) << '<' << __FUNCTION__ << window()
@@ -1958,8 +2007,11 @@ void QWindowsBaseWindow::setGeometry_sys(const QRect &rect) const
 
 HDC QWindowsWindow::getDC()
 {
-    if (!m_hdc)
+    if (!m_hdc) {
         m_hdc = GetDC(handle());
+        if (QGuiApplication::layoutDirection() == Qt::RightToLeft)
+            SetLayout(m_hdc, 0); // Clear RTL layout
+    }
     return m_hdc;
 }
 
diff --git a/src/plugins/platforms/windows/qwindowswindow.h b/src/plugins/platforms/windows/qwindowswindow.h
index 958564aa86..1abe1e3531 100644
--- a/src/plugins/platforms/windows/qwindowswindow.h
+++ b/src/plugins/platforms/windows/qwindowswindow.h
@@ -89,7 +89,8 @@ struct QWindowCreationContext
     const QWindow *window;
     QRect requestedGeometryIn; // QWindow scaled
     QRect requestedGeometry; // after QPlatformWindow::initialGeometry()
-    QRect obtainedGeometry;
+    QPoint obtainedPos;
+    QSize obtainedSize;
     QMargins margins;
     QMargins customMargins;  // User-defined, additional frame for WM_NCCALCSIZE
     int frameX = CW_USEDEFAULT; // Passed on to CreateWindowEx(), including frame.
@@ -134,6 +135,7 @@ public:
 
     unsigned style() const   { return GetWindowLongPtr(handle(), GWL_STYLE); }
     unsigned exStyle() const { return GetWindowLongPtr(handle(), GWL_EXSTYLE); }
+    static bool isRtlLayout(HWND hwnd);
 
     static QWindowsBaseWindow *baseWindowOf(const QWindow *w);
     static HWND handleOf(const QWindow *w);
@@ -399,18 +401,38 @@ QDebug operator<<(QDebug d, const WINDOWPOS &);
 QDebug operator<<(QDebug d, const GUID &guid);
 #endif // !QT_NO_DEBUG_STREAM
 
+static inline void clientToScreen(HWND hwnd, POINT *wP)
+{
+    if (QWindowsBaseWindow::isRtlLayout(hwnd)) {
+        RECT clientArea;
+        GetClientRect(hwnd, &clientArea);
+        wP->x = clientArea.right - wP->x;
+    }
+    ClientToScreen(hwnd, wP);
+}
+
+static inline void screenToClient(HWND hwnd, POINT *wP)
+{
+    ScreenToClient(hwnd, wP);
+    if (QWindowsBaseWindow::isRtlLayout(hwnd)) {
+        RECT clientArea;
+        GetClientRect(hwnd, &clientArea);
+        wP->x = clientArea.right - wP->x;
+    }
+}
+
 // ---------- QWindowsGeometryHint inline functions.
 QPoint QWindowsGeometryHint::mapToGlobal(HWND hwnd, const QPoint &qp)
 {
     POINT p = { qp.x(), qp.y() };
-    ClientToScreen(hwnd, &p);
+    clientToScreen(hwnd, &p);
     return QPoint(p.x, p.y);
 }
 
 QPoint QWindowsGeometryHint::mapFromGlobal(const HWND hwnd, const QPoint &qp)
 {
     POINT p = { qp.x(), qp.y() };
-    ScreenToClient(hwnd, &p);
+    screenToClient(hwnd, &p);
     return QPoint(p.x, p.y);
 }