winrt: Fix input grabbing

Beside its usage in widgets, mouse grabs are required for QML menus to
work.

Task-number: QTBUG-57079
Change-Id: I306cb68624186da69725470e147bc7b979dac8e4
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>

src/plugins/platforms/winrt/qwinrtscreen.cpp

@@ -486,6 +486,9 @@ public:
     QHash<ApplicationView2CallbackRemover, EventRegistrationToken> view2Tokens;
     ComPtr<IApplicationView2> view2;
 #endif // WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_PHONE_APP)
+    QAtomicPointer<QWinRTWindow> mouseGrabWindow;
+    QAtomicPointer<QWinRTWindow> keyboardGrabWindow;
+    QWindow *currentPressWindow = 0;
 };
 
 // To be called from the XAML thread
@@ -877,6 +880,44 @@ void QWinRTScreen::lower(QWindow *window)
     handleExpose();
 }
 
+bool QWinRTScreen::setMouseGrabWindow(QWinRTWindow *window, bool grab)
+{
+    Q_D(QWinRTScreen);
+    qCDebug(lcQpaWindows) << __FUNCTION__ << window
+                          << "(" << window->window()->objectName() << "):" << grab;
+
+    if (!grab || window == nullptr)
+        d->mouseGrabWindow = nullptr;
+    else if (d->mouseGrabWindow != window)
+        d->mouseGrabWindow = window;
+    return grab;
+}
+
+QWinRTWindow *QWinRTScreen::mouseGrabWindow() const
+{
+    Q_D(const QWinRTScreen);
+    return d->mouseGrabWindow;
+}
+
+bool QWinRTScreen::setKeyboardGrabWindow(QWinRTWindow *window, bool grab)
+{
+    Q_D(QWinRTScreen);
+    qCDebug(lcQpaWindows) << __FUNCTION__ << window
+                          << "(" << window->window()->objectName() << "):" << grab;
+
+    if (!grab || window == nullptr)
+        d->keyboardGrabWindow = nullptr;
+    else if (d->keyboardGrabWindow != window)
+        d->keyboardGrabWindow = window;
+    return grab;
+}
+
+QWinRTWindow *QWinRTScreen::keyboardGrabWindow() const
+{
+    Q_D(const QWinRTScreen);
+    return d->keyboardGrabWindow;
+}
+
 void QWinRTScreen::updateWindowTitle(const QString &title)
 {
     Q_D(QWinRTScreen);
@@ -1022,7 +1063,11 @@ HRESULT QWinRTScreen::onPointerEntered(ICoreWindow *, IPointerEventArgs *args)
         pointerPoint->get_Position(&point);
         QPoint pos(point.X * d->scaleFactor, point.Y * d->scaleFactor);
 
-        QWindowSystemInterface::handleEnterEvent(topWindow(), pos, pos);
+        QWindow *targetWindow = topWindow();
+        if (d->mouseGrabWindow)
+            targetWindow = d->mouseGrabWindow.load()->window();
+
+        QWindowSystemInterface::handleEnterEvent(targetWindow, pos, pos);
     }
     return S_OK;
 }
@@ -1041,7 +1086,11 @@ HRESULT QWinRTScreen::onPointerExited(ICoreWindow *, IPointerEventArgs *args)
 
     d->touchPoints.remove(id);
 
-    QWindowSystemInterface::handleLeaveEvent(0);
+    QWindow *targetWindow = nullptr;
+    if (d->mouseGrabWindow)
+        targetWindow = d->mouseGrabWindow.load()->window();
+
+    QWindowSystemInterface::handleLeaveEvent(targetWindow);
     return S_OK;
 }
 
@@ -1063,7 +1112,12 @@ HRESULT QWinRTScreen::onPointerUpdated(ICoreWindow *, IPointerEventArgs *args)
     QPointF localPos = pos;
 
     const QPoint posPoint = pos.toPoint();
-    QWindow *targetWindow = windowAt(posPoint);
+    QWindow *windowUnderPointer = windowAt(posPoint);
+    QWindow *targetWindow = windowUnderPointer;
+
+    if (d->mouseGrabWindow)
+        targetWindow = d->mouseGrabWindow.load()->window();
+
     if (targetWindow) {
         const QPointF globalPosDelta = pos - posPoint;
         localPos = targetWindow->mapFromGlobal(posPoint) + globalPosDelta;
@@ -1127,6 +1181,22 @@ HRESULT QWinRTScreen::onPointerUpdated(ICoreWindow *, IPointerEventArgs *args)
         if (isPressed)
             buttons |= Qt::XButton2;
 
+        // In case of a mouse grab we have to store the target of a press event
+        // to be able to send one additional release event to this target when the mouse
+        // button is released. This is a similar approach to AutoMouseCapture in the
+        // windows qpa backend. Otherwise the release might not be propagated and the original
+        // press event receiver considers a button to still be pressed, as in Qt Quick Controls 1
+        // menus.
+        if (buttons != Qt::NoButton && d->currentPressWindow == nullptr && !d->mouseGrabWindow)
+            d->currentPressWindow = windowUnderPointer;
+        if (!isPressed && d->currentPressWindow && d->mouseGrabWindow) {
+            const QPointF globalPosDelta = pos - posPoint;
+            const QPointF localPressPos = d->currentPressWindow->mapFromGlobal(posPoint) + globalPosDelta;
+
+            QWindowSystemInterface::handleMouseEvent(d->currentPressWindow, localPressPos, pos, buttons, mods);
+            d->currentPressWindow = nullptr;
+        }
+
         QWindowSystemInterface::handleMouseEvent(targetWindow, localPos, pos, buttons, mods);
 
         break;

src/plugins/platforms/winrt/qwinrtscreen.h

@@ -83,6 +83,7 @@ class QTouchDevice;
 class QWinRTCursor;
 class QWinRTInputContext;
 class QWinRTScreenPrivate;
+class QWinRTWindow;
 class QWinRTScreen : public QPlatformScreen
 {
 public:
@@ -110,6 +111,12 @@ public:
     void raise(QWindow *window);
     void lower(QWindow *window);
 
+    bool setMouseGrabWindow(QWinRTWindow *window, bool grab);
+    QWinRTWindow* mouseGrabWindow() const;
+
+    bool setKeyboardGrabWindow(QWinRTWindow *window, bool grab);
+    QWinRTWindow* keyboardGrabWindow() const;
+
     void updateWindowTitle(const QString &title);
 
     ABI::Windows::UI::Core::ICoreWindow *coreWindow() const;

src/plugins/platforms/winrt/qwinrtwindow.cpp

@@ -191,6 +191,11 @@ QWinRTWindow::~QWinRTWindow()
     });
     RETURN_VOID_IF_FAILED("Failed to completely destroy window resources, likely because the application is shutting down");
 
+    if (d->screen->mouseGrabWindow() == this)
+        d->screen->setMouseGrabWindow(this, false);
+    if (d->screen->keyboardGrabWindow() == this)
+        d->screen->setKeyboardGrabWindow(this, false);
+
     d->screen->removeWindow(window());
 
     if (!d->surface)
@@ -384,6 +389,24 @@ void QWinRTWindow::setWindowState(Qt::WindowState state)
     d->state = state;
 }
 
+bool QWinRTWindow::setMouseGrabEnabled(bool grab)
+{
+    Q_D(QWinRTWindow);
+    if (!isActive() && grab) {
+        qWarning("%s: Not setting mouse grab for invisible window %s/'%s'",
+                 __FUNCTION__, window()->metaObject()->className(),
+                 qPrintable(window()->objectName()));
+        return false;
+    }
+    return d->screen->setMouseGrabWindow(this, grab);
+}
+
+bool QWinRTWindow::setKeyboardGrabEnabled(bool grab)
+{
+    Q_D(QWinRTWindow);
+    return d->screen->setKeyboardGrabWindow(this, grab);
+}
+
 EGLSurface QWinRTWindow::eglSurface() const
 {
     Q_D(const QWinRTWindow);

src/plugins/platforms/winrt/qwinrtwindow.h

@@ -70,6 +70,9 @@ public:
     qreal devicePixelRatio() const Q_DECL_OVERRIDE;
     void setWindowState(Qt::WindowState state) Q_DECL_OVERRIDE;
 
+    bool setMouseGrabEnabled(bool grab) Q_DECL_OVERRIDE;
+    bool setKeyboardGrabEnabled(bool grab) Q_DECL_OVERRIDE;
+
     EGLSurface eglSurface() const;
     void createEglSurface(EGLDisplay display, EGLConfig config);