Refactor code focused around QWasmCompositor::processMouse

Refactoring of the logic around QWasmCompositor::processMouse has been
performed for readability and easier modification, in preparation for
further fixes for event delivery and handling in windows. There should
be no logic changes, just cleaner code.

Change groups:
Members of QWasmCompositor have been prefixed by m_ for easier discerning
of stateful and stateless variables in functions.

Variables renamed to more descriptive, e.g. window2->targetWindow,
globalPoint->targetPointInScreenCoords.

Magic numbers eliminated, e.g. mouseEvent->button == 0 is now
button == Qt::MouseButton::LeftButton.

Some common condition checks have been wrapped into single constants,
e.g. !(htmlWindow->m_windowState & Qt::WindowFullScreen) &&
!(htmlWindow->m_windowState & Qt::WindowMaximized) ==
isTargetWindowResizable

Some nested if-conditions were collapsed.

Some unnecessary checks have been moved to outer if conditions (e.g. for
draggedWindow in EMSCRIPTEN_EVENT_MOUSEMOVE, since the code would crash
anyway because only some parts are guarded against it being nullptr).

Consts introduced so that variables are only used for one purpose.

Made QWasmEventTranslator::translateMouseButton constexpr

Made QWasmWindow::isPointOnTitle behave correctly when the window has
no title bar so that no flag probing is needed prior to calling it.

Made QWasmCursor::setOverrideWasmCursor accept a const ref - having it
accept pointer suggested it might dangle.

Change-Id: I8910622fddad764ee86eb0260b5ad23c7ee7f97a
Reviewed-by: David Skoland <david.skoland@qt.io>

7 files changed, 207 insertions, 229 deletions

diff --git a/src/plugins/platforms/wasm/qwasmcompositor.cpp b/src/plugins/platforms/wasm/qwasmcompositor.cpp
index 7787367e01..920a8bf016 100644
--- a/src/plugins/platforms/wasm/qwasmcompositor.cpp
+++ b/src/plugins/platforms/wasm/qwasmcompositor.cpp
@@ -25,6 +25,12 @@
 
 #include <emscripten/bind.h>
 
+namespace {
+QWasmWindow *AsWasmWindow(QWindow *window) {
+    return static_cast<QWasmWindow*>(window->handle());
+}
+}  // namespace
+
 using namespace emscripten;
 
 Q_GUI_EXPORT int qt_defaultDpiX();
@@ -51,32 +57,22 @@ EMSCRIPTEN_BINDINGS(qtMouseModule) {
 }
 
 QWasmCompositor::QWasmCompositor(QWasmScreen *screen)
-    :QObject(screen)
+    : QObject(screen)
     , m_blitter(new QOpenGLTextureBlitter)
-    , m_needComposit(false)
-    , m_inFlush(false)
-    , m_inResize(false)
-    , m_isEnabled(true)
-    , m_targetDevicePixelRatio(1)
-    , draggedWindow(nullptr)
-    , lastWindow(nullptr)
-    , pressedButtons(Qt::NoButton)
-    , resizeMode(QWasmCompositor::ResizeNone)
-    , eventTranslator(new QWasmEventTranslator())
-    , mouseInCanvas(false)
+    , m_eventTranslator(std::make_unique<QWasmEventTranslator>())
 {
-    touchDevice = new QPointingDevice(
+    m_touchDevice = std::make_unique<QPointingDevice>(
             "touchscreen", 1, QInputDevice::DeviceType::TouchScreen,
             QPointingDevice::PointerType::Finger,
             QPointingDevice::Capability::Position | QPointingDevice::Capability::Area
                 | QPointingDevice::Capability::NormalizedPosition,
             10, 0);
-    QWindowSystemInterface::registerInputDevice(touchDevice);
+    QWindowSystemInterface::registerInputDevice(m_touchDevice.get());
 }
 
 QWasmCompositor::~QWasmCompositor()
 {
-    windowUnderMouse.clear();
+    m_windowUnderMouse.clear();
 
     if (m_requestAnimationFrameId != -1)
         emscripten_cancel_animation_frame(m_requestAnimationFrameId);
@@ -137,7 +133,7 @@ void QWasmCompositor::initEventHandlers()
 {
     QByteArray canvasSelector = screen()->canvasTargetId().toUtf8();
 
-    eventTranslator->g_usePlatformMacSpecifics
+    m_eventTranslator->g_usePlatformMacSpecifics
     = (QWasmIntegration::get()->platform == QWasmIntegration::MacOSPlatform);
     if (QWasmIntegration::get()->platform == QWasmIntegration::MacOSPlatform) {
         if (!emscripten::val::global("window")["safari"].isUndefined()) {
@@ -148,23 +144,25 @@ void QWasmCompositor::initEventHandlers()
         }
     }
 
-    emscripten_set_keydown_callback(canvasSelector.constData(), (void *)this, 1, &keyboard_cb);
-    emscripten_set_keyup_callback(canvasSelector.constData(), (void *)this, 1, &keyboard_cb);
+    constexpr EM_BOOL UseCapture = 1;
+
+    emscripten_set_keydown_callback(canvasSelector.constData(), (void *)this, UseCapture, &keyboard_cb);
+    emscripten_set_keyup_callback(canvasSelector.constData(), (void *)this, UseCapture, &keyboard_cb);
 
-    emscripten_set_mousedown_callback(canvasSelector.constData(), (void *)this, 1, &mouse_cb);
-    emscripten_set_mouseup_callback(canvasSelector.constData(), (void *)this, 1, &mouse_cb);
-    emscripten_set_mousemove_callback(canvasSelector.constData(), (void *)this, 1, &mouse_cb);
-    emscripten_set_mouseenter_callback(canvasSelector.constData(), (void *)this, 1, &mouse_cb);
-    emscripten_set_mouseleave_callback(canvasSelector.constData(), (void *)this, 1, &mouse_cb);
+    emscripten_set_mousedown_callback(canvasSelector.constData(), (void *)this, UseCapture, &mouse_cb);
+    emscripten_set_mouseup_callback(canvasSelector.constData(), (void *)this, UseCapture, &mouse_cb);
+    emscripten_set_mousemove_callback(canvasSelector.constData(), (void *)this, UseCapture, &mouse_cb);
+    emscripten_set_mouseenter_callback(canvasSelector.constData(), (void *)this, UseCapture, &mouse_cb);
+    emscripten_set_mouseleave_callback(canvasSelector.constData(), (void *)this, UseCapture, &mouse_cb);
 
-    emscripten_set_focus_callback(canvasSelector.constData(), (void *)this, 1, &focus_cb);
+    emscripten_set_focus_callback(canvasSelector.constData(), (void *)this, UseCapture, &focus_cb);
 
-    emscripten_set_wheel_callback(canvasSelector.constData(), (void *)this, 1, &wheel_cb);
+    emscripten_set_wheel_callback(canvasSelector.constData(), (void *)this, UseCapture, &wheel_cb);
 
-    emscripten_set_touchstart_callback(canvasSelector.constData(), (void *)this, 1, &touchCallback);
-    emscripten_set_touchend_callback(canvasSelector.constData(), (void *)this, 1, &touchCallback);
-    emscripten_set_touchmove_callback(canvasSelector.constData(), (void *)this, 1, &touchCallback);
-    emscripten_set_touchcancel_callback(canvasSelector.constData(), (void *)this, 1, &touchCallback);
+    emscripten_set_touchstart_callback(canvasSelector.constData(), (void *)this, UseCapture, &touchCallback);
+    emscripten_set_touchend_callback(canvasSelector.constData(), (void *)this, UseCapture, &touchCallback);
+    emscripten_set_touchmove_callback(canvasSelector.constData(), (void *)this, UseCapture, &touchCallback);
+    emscripten_set_touchcancel_callback(canvasSelector.constData(), (void *)this, UseCapture, &touchCallback);
 
     val canvas = screen()->canvas();
     canvas.call<void>("addEventListener",
@@ -208,9 +206,9 @@ void QWasmCompositor::removeWindow(QWasmWindow *window)
     m_requestUpdateWindows.remove(window);
 
     if (!m_windowStack.isEmpty() && !QGuiApplication::focusWindow()) {
-        auto lastWindow = m_windowStack.last();
-        lastWindow->requestActivateWindow();
-        notifyTopWindowChanged(lastWindow);
+        auto m_lastMouseTargetWindow = m_windowStack.last();
+        m_lastMouseTargetWindow->requestActivateWindow();
+        notifyTopWindowChanged(m_lastMouseTargetWindow);
     }
 }
 
@@ -268,7 +266,7 @@ int QWasmCompositor::windowCount() const
     return m_windowStack.count();
 }
 
-QWindow *QWasmCompositor::windowAt(QPoint globalPoint, int padding) const
+QWindow *QWasmCompositor::windowAt(QPoint targetPointInScreenCoords, int padding) const
 {
     int index = m_windowStack.count() - 1;
     // qDebug() << "window at" << "point" << p << "window count" << index;
@@ -280,7 +278,7 @@ QWindow *QWasmCompositor::windowAt(QPoint globalPoint, int padding) const
         QRect geometry = compositedWindow.window->windowFrameGeometry()
                          .adjusted(-padding, -padding, padding, padding);
 
-        if (compositedWindow.visible && geometry.contains(globalPoint))
+        if (compositedWindow.visible && geometry.contains(targetPointInScreenCoords))
             return m_windowStack.at(index)->window();
         --index;
     }
@@ -920,11 +918,11 @@ void QWasmCompositor::resizeWindow(QWindow *window, QWasmCompositor::ResizeMode
 void QWasmCompositor::notifyTopWindowChanged(QWasmWindow *window)
 {
     QWindow *modalWindow;
-    bool blocked = QGuiApplicationPrivate::instance()->isWindowBlocked(window->window(), &modalWindow);
+    bool isTargetWindowBlocked = QGuiApplicationPrivate::instance()->isWindowBlocked(window->window(), &modalWindow);
 
-    if (blocked) {
+    if (isTargetWindowBlocked) {
         modalWindow->requestActivate();
-        raise(static_cast<QWasmWindow*>(modalWindow->handle()));
+        raise(AsWasmWindow(modalWindow));
         return;
     }
 
@@ -976,162 +974,146 @@ int QWasmCompositor::touchCallback(int eventType, const EmscriptenTouchEvent *to
 
 bool QWasmCompositor::processMouse(int eventType, const EmscriptenMouseEvent *mouseEvent)
 {
-    QPoint targetPoint(mouseEvent->targetX, mouseEvent->targetY);
-    QPoint globalPoint = screen()->geometry().topLeft() + targetPoint;
+    const Qt::MouseButton button = QWasmEventTranslator::translateMouseButton(mouseEvent->button);
+
+    const QPoint targetPointInCanvasCoords(mouseEvent->targetX, mouseEvent->targetY);
+    const QPoint targetPointInScreenCoords = screen()->geometry().topLeft() + targetPointInCanvasCoords;
 
     QEvent::Type buttonEventType = QEvent::None;
-    Qt::MouseButton button = Qt::NoButton;
-    Qt::KeyboardModifiers modifiers = eventTranslator->translateMouseEventModifier(mouseEvent);
+    Qt::KeyboardModifiers modifiers = m_eventTranslator->translateMouseEventModifier(mouseEvent);
 
-    QWindow *window2 = nullptr;
-    if (resizeMode == QWasmCompositor::ResizeNone)
-        window2 = screen()->compositor()->windowAt(globalPoint, 5);
+    QWindow *const targetWindow = ([this, &targetPointInScreenCoords]() -> QWindow * {
+        auto *targetWindow =
+            m_resizeMode == QWasmCompositor::ResizeNone ?
+                screen()->compositor()->windowAt(targetPointInScreenCoords, 5) : nullptr;
 
-    if (window2 == nullptr) {
-        window2 = lastWindow;
-    } else {
-        lastWindow = window2;
-    }
+        return targetWindow ? targetWindow : m_lastMouseTargetWindow.get();
+    })();
+    if (targetWindow)
+        m_lastMouseTargetWindow = targetWindow;
 
-    QPoint localPoint = window2->mapFromGlobal(globalPoint);
-    bool interior = window2->geometry().contains(globalPoint);
-    bool blocked = QGuiApplicationPrivate::instance()->isWindowBlocked(window2);
+    const QPoint pointInTargetWindowCoords = targetWindow->mapFromGlobal(targetPointInScreenCoords);
+    const bool pointerIsWithinTargetWindowBounds = targetWindow->geometry().contains(targetPointInScreenCoords);
+    const bool isTargetWindowBlocked = QGuiApplicationPrivate::instance()->isWindowBlocked(targetWindow);
 
-    if (mouseInCanvas) {
-        if (windowUnderMouse != window2 && interior) {
+    if (m_mouseInCanvas && m_windowUnderMouse != targetWindow && pointerIsWithinTargetWindowBounds) {
         // delayed mouse enter
-            enterWindow(window2, localPoint, globalPoint);
-            windowUnderMouse = window2;
-        }
+        enterWindow(targetWindow, pointInTargetWindowCoords, targetPointInScreenCoords);
+        m_windowUnderMouse = targetWindow;
     }
 
-    QWasmWindow *htmlWindow = static_cast<QWasmWindow*>(window2->handle());
-    Qt::WindowStates windowState = htmlWindow->window()->windowState();
-    bool isResizable = !(windowState.testFlag(Qt::WindowMaximized) ||
-                         windowState.testFlag(Qt::WindowFullScreen));
+    QWasmWindow *wasmTargetWindow = AsWasmWindow(targetWindow);
+    Qt::WindowStates windowState = targetWindow->windowState();
+    const bool isTargetWindowResizable = !windowState.testFlag(Qt::WindowMaximized) && !windowState.testFlag(Qt::WindowFullScreen);
 
     switch (eventType) {
     case EMSCRIPTEN_EVENT_MOUSEDOWN:
     {
-        button = QWasmEventTranslator::translateMouseButton(mouseEvent->button);
-
-        if (window2)
-            window2->requestActivate();
+        buttonEventType = QEvent::MouseButtonPress;
+        m_pressedButtons.setFlag(button);
 
-        pressedButtons.setFlag(button);
+        if (targetWindow)
+            targetWindow->requestActivate();
 
-        pressedWindow = window2;
-        buttonEventType = QEvent::MouseButtonPress;
+        m_pressedWindow = targetWindow;
 
-        // button overview:
-        // 0 = primary mouse button, usually left click
-        // 1 = middle mouse button, usually mouse wheel
-        // 2 = right mouse button, usually right click
-        // from: https://w3c.github.io/uievents/#dom-mouseevent-button
-        if (mouseEvent->button == 0) {
-            if (!blocked && !(htmlWindow->m_windowState & Qt::WindowFullScreen)
-                    && !(htmlWindow->m_windowState & Qt::WindowMaximized)) {
-                if (htmlWindow && window2->flags().testFlag(Qt::WindowTitleHint)
-                        && htmlWindow->isPointOnTitle(globalPoint))
-                    draggedWindow = window2;
-                else if (htmlWindow && htmlWindow->isPointOnResizeRegion(globalPoint)) {
-                    draggedWindow = window2;
-                    resizeMode = htmlWindow->resizeModeAtPoint(globalPoint);
-                    resizePoint = globalPoint;
-                    resizeStartRect = window2->geometry();
-                }
+        if (isTargetWindowResizable && button == Qt::MouseButton::LeftButton && !isTargetWindowBlocked) {
+            if (wasmTargetWindow->isPointOnTitle(targetPointInScreenCoords)) {
+                m_windowBeingManipulated = targetWindow;
+            } else if (wasmTargetWindow->isPointOnResizeRegion(targetPointInScreenCoords)) {
+                m_windowBeingManipulated = targetWindow;
+                m_resizeMode = wasmTargetWindow->resizeModeAtPoint(targetPointInScreenCoords);
+                m_resizePoint = targetPointInScreenCoords;
+                m_resizeStartRect = targetWindow->geometry();
             }
         }
 
-        htmlWindow->injectMousePressed(localPoint, globalPoint, button, modifiers);
+        wasmTargetWindow->injectMousePressed(pointInTargetWindowCoords, targetPointInScreenCoords, button, modifiers);
         break;
     }
     case EMSCRIPTEN_EVENT_MOUSEUP:
     {
-        button = QWasmEventTranslator::translateMouseButton(mouseEvent->button);
-        pressedButtons.setFlag(button, false);
         buttonEventType = QEvent::MouseButtonRelease;
-        QWasmWindow *oldWindow = nullptr;
 
-        if (mouseEvent->button == 0 && pressedWindow) {
-            oldWindow = static_cast<QWasmWindow*>(pressedWindow->handle());
-            pressedWindow = nullptr;
-        }
+        m_pressedButtons.setFlag(button, false);
 
-        if (draggedWindow && pressedButtons.testFlag(Qt::NoButton)) {
-            draggedWindow = nullptr;
-            resizeMode = QWasmCompositor::ResizeNone;
+        if (m_windowBeingManipulated && m_pressedButtons.testFlag(Qt::NoButton)) {
+            m_windowBeingManipulated = nullptr;
+            m_resizeMode = QWasmCompositor::ResizeNone;
         }
 
-        if (oldWindow)
-            oldWindow->injectMouseReleased(localPoint, globalPoint, button, modifiers);
-        else
-            htmlWindow->injectMouseReleased(localPoint, globalPoint, button, modifiers);
+        if (m_pressedWindow) {
+            // Always deliver the released event to the same window that was pressed
+            AsWasmWindow(m_pressedWindow)->injectMouseReleased(pointInTargetWindowCoords, targetPointInScreenCoords, button, modifiers);
+            if (button == Qt::MouseButton::LeftButton)
+                m_pressedWindow = nullptr;
+        } else {
+            wasmTargetWindow->injectMouseReleased(pointInTargetWindowCoords, targetPointInScreenCoords, button, modifiers);
+        }
         break;
     }
-    case EMSCRIPTEN_EVENT_MOUSEMOVE: // drag event
+    case EMSCRIPTEN_EVENT_MOUSEMOVE:
     {
         buttonEventType = QEvent::MouseMove;
 
-        if (htmlWindow && pressedButtons.testFlag(Qt::NoButton)) {
+        if (wasmTargetWindow && m_pressedButtons.testFlag(Qt::NoButton)) {
+            const bool isOnResizeRegion = wasmTargetWindow->isPointOnResizeRegion(targetPointInScreenCoords);
 
-            bool isOnResizeRegion = htmlWindow->isPointOnResizeRegion(globalPoint);
+            if (isTargetWindowResizable && isOnResizeRegion && !isTargetWindowBlocked) {
+                const QCursor resizingCursor = QWasmEventTranslator::cursorForMode(
+                    wasmTargetWindow->resizeModeAtPoint(targetPointInScreenCoords));
 
-            if (isResizable && isOnResizeRegion && !blocked) {
-                QCursor resizingCursor = eventTranslator->cursorForMode(htmlWindow->resizeModeAtPoint(globalPoint));
-
-                if (resizingCursor != window2->cursor()) {
-                    isCursorOverridden = true;
-                    QWasmCursor::setOverrideWasmCursor(&resizingCursor, window2->screen());
-                }
-            } else { // off resizing area
-                if (isCursorOverridden) {
-                    isCursorOverridden = false;
-                    QWasmCursor::clearOverrideWasmCursor(window2->screen());
+                if (resizingCursor != targetWindow->cursor()) {
+                    m_isResizeCursorDisplayed = true;
+                    QWasmCursor::setOverrideWasmCursor(resizingCursor, targetWindow->screen());
                 }
+            } else if (m_isResizeCursorDisplayed) {  // off resizing area
+                m_isResizeCursorDisplayed = false;
+                QWasmCursor::clearOverrideWasmCursor(targetWindow->screen());
             }
         }
 
-        if (!(htmlWindow->m_windowState & Qt::WindowFullScreen) && !(htmlWindow->m_windowState & Qt::WindowMaximized)) {
-            if (resizeMode == QWasmCompositor::ResizeNone && draggedWindow) {
-                draggedWindow->setX(draggedWindow->x() + mouseEvent->movementX);
-                draggedWindow->setY(draggedWindow->y() + mouseEvent->movementY);
-            }
-
-            if (resizeMode != QWasmCompositor::ResizeNone && !(htmlWindow->m_windowState & Qt::WindowFullScreen)) {
-                QPoint delta = QPoint(mouseEvent->targetX, mouseEvent->targetY) - resizePoint;
-                resizeWindow(draggedWindow, resizeMode, resizeStartRect, delta);
+        if (m_windowBeingManipulated && isTargetWindowResizable) {
+            if (m_resizeMode == QWasmCompositor::ResizeNone) {
+                m_windowBeingManipulated->setPosition(
+                    m_windowBeingManipulated->position() + QPoint(mouseEvent->movementX, mouseEvent->movementY));
+            } else {
+                const QPoint delta = targetPointInCanvasCoords - m_resizePoint;
+                resizeWindow(m_windowBeingManipulated, m_resizeMode, m_resizeStartRect, delta);
             }
         }
         break;
     }
-        case EMSCRIPTEN_EVENT_MOUSEENTER:
-            processMouseEnter(mouseEvent);
+    case EMSCRIPTEN_EVENT_MOUSEENTER:
+        processMouseEnter(mouseEvent);
+        break;
+    case EMSCRIPTEN_EVENT_MOUSELEAVE:
+        processMouseLeave();
         break;
-        case EMSCRIPTEN_EVENT_MOUSELEAVE:
-            processMouseLeave();
+    default:
         break;
-    default:        break;
     };
 
-    if (!interior && pressedButtons.testFlag(Qt::NoButton)) {
-        leaveWindow(lastWindow);
+    if (!pointerIsWithinTargetWindowBounds && m_pressedButtons.testFlag(Qt::NoButton)) {
+        leaveWindow(m_lastMouseTargetWindow);
     }
 
-    if (!window2 && buttonEventType == QEvent::MouseButtonRelease) {
-        window2 = lastWindow;
-        lastWindow = nullptr;
-        interior = true;
-    }
-    bool accepted = false;
-    if (window2 && interior) {
-        accepted = QWindowSystemInterface::handleMouseEvent<QWindowSystemInterface::SynchronousDelivery>(
-                window2, QWasmIntegration::getTimestamp(), localPoint, globalPoint, pressedButtons, button, buttonEventType, modifiers);
+    bool shouldDeliverEvent = pointerIsWithinTargetWindowBounds;
+    QWindow *eventTarget = targetWindow;
+    if (!eventTarget && buttonEventType == QEvent::MouseButtonRelease) {
+        eventTarget = m_lastMouseTargetWindow;
+        m_lastMouseTargetWindow = nullptr;
+        shouldDeliverEvent = true;
     }
+    const bool eventAccepted =
+        eventTarget != nullptr && shouldDeliverEvent &&
+        QWindowSystemInterface::handleMouseEvent<QWindowSystemInterface::SynchronousDelivery>(
+            eventTarget, QWasmIntegration::getTimestamp(), pointInTargetWindowCoords, targetPointInScreenCoords,
+            m_pressedButtons, button, buttonEventType, modifiers);
 
-    if (eventType == EMSCRIPTEN_EVENT_MOUSEDOWN && !accepted)
+    if (!eventAccepted && buttonEventType == QEvent::MouseButtonPress)
         QGuiApplicationPrivate::instance()->closeAllPopups();
-    return accepted;
+    return eventAccepted;
 }
 
 bool QWasmCompositor::processKeyboard(int eventType, const EmscriptenKeyboardEvent *keyEvent)
@@ -1143,12 +1125,12 @@ bool QWasmCompositor::processKeyboard(int eventType, const EmscriptenKeyboardEve
         case EMSCRIPTEN_EVENT_KEYPRESS:
         case EMSCRIPTEN_EVENT_KEYDOWN: // down
             keyType = QEvent::KeyPress;
-            qtKey = this->eventTranslator->getKey(keyEvent);
-            keyText = this->eventTranslator->getKeyText(keyEvent, qtKey);
+            qtKey = m_eventTranslator->getKey(keyEvent);
+            keyText = m_eventTranslator->getKeyText(keyEvent, qtKey);
             break;
         case EMSCRIPTEN_EVENT_KEYUP: // up
             keyType = QEvent::KeyRelease;
-            this->eventTranslator->setStickyDeadKey(keyEvent);
+            m_eventTranslator->setStickyDeadKey(keyEvent);
             break;
         default:
             break;
@@ -1157,7 +1139,7 @@ bool QWasmCompositor::processKeyboard(int eventType, const EmscriptenKeyboardEve
     if (keyType == QEvent::None)
         return 0;
 
-    QFlags<Qt::KeyboardModifier> modifiers = eventTranslator->translateKeyboardEventModifier(keyEvent);
+    QFlags<Qt::KeyboardModifier> modifiers = m_eventTranslator->translateKeyboardEventModifier(keyEvent);
 
     // Clipboard fallback path: cut/copy/paste are handled by clipboard event
     // handlers if direct clipboard access is not available.
@@ -1215,14 +1197,14 @@ bool QWasmCompositor::processWheel(int eventType, const EmscriptenWheelEvent *wh
 
     scrollFactor = -scrollFactor; // Web scroll deltas are inverted from Qt deltas.
 
-    Qt::KeyboardModifiers modifiers = eventTranslator->translateMouseEventModifier(&mouseEvent);
-    QPoint targetPoint(mouseEvent.targetX, mouseEvent.targetY);
-    QPoint globalPoint = screen()->geometry().topLeft() + targetPoint;
+    Qt::KeyboardModifiers modifiers = m_eventTranslator->translateMouseEventModifier(&mouseEvent);
+    QPoint targetPointInCanvasCoords(mouseEvent.targetX, mouseEvent.targetY);
+    QPoint targetPointInScreenCoords = screen()->geometry().topLeft() + targetPointInCanvasCoords;
 
-    QWindow *window2 = screen()->compositor()->windowAt(globalPoint, 5);
-    if (!window2)
+    QWindow *targetWindow = screen()->compositor()->windowAt(targetPointInScreenCoords, 5);
+    if (!targetWindow)
         return 0;
-    QPoint localPoint = window2->mapFromGlobal(globalPoint);
+    QPoint pointInTargetWindowCoords = targetWindow->mapFromGlobal(targetPointInScreenCoords);
 
     QPoint pixelDelta;
 
@@ -1232,8 +1214,8 @@ bool QWasmCompositor::processWheel(int eventType, const EmscriptenWheelEvent *wh
     QPoint angleDelta = pixelDelta; // FIXME: convert from pixels?
 
     bool accepted = QWindowSystemInterface::handleWheelEvent(
-            window2, QWasmIntegration::getTimestamp(), localPoint,
-            globalPoint, pixelDelta, angleDelta, modifiers,
+            targetWindow, QWasmIntegration::getTimestamp(), pointInTargetWindowCoords,
+            targetPointInScreenCoords, pixelDelta, angleDelta, modifiers,
             Qt::NoScrollPhase, Qt::MouseEventNotSynthesized,
             g_scrollingInvertedFromDevice);
     return accepted;
@@ -1243,17 +1225,17 @@ int QWasmCompositor::handleTouch(int eventType, const EmscriptenTouchEvent *touc
 {
     QList<QWindowSystemInterface::TouchPoint> touchPointList;
     touchPointList.reserve(touchEvent->numTouches);
-    QWindow *window2;
+    QWindow *targetWindow;
 
     for (int i = 0; i < touchEvent->numTouches; i++) {
 
         const EmscriptenTouchPoint *touches = &touchEvent->touches[i];
 
-        QPoint targetPoint(touches->targetX, touches->targetY);
-        QPoint globalPoint = screen()->geometry().topLeft() + targetPoint;
+        QPoint targetPointInCanvasCoords(touches->targetX, touches->targetY);
+        QPoint targetPointInScreenCoords = screen()->geometry().topLeft() + targetPointInCanvasCoords;
 
-        window2 = this->screen()->compositor()->windowAt(globalPoint, 5);
-        if (window2 == nullptr)
+        targetWindow = screen()->compositor()->windowAt(targetPointInScreenCoords, 5);
+        if (targetWindow == nullptr)
             continue;
 
         QWindowSystemInterface::TouchPoint touchPoint;
@@ -1262,41 +1244,41 @@ int QWasmCompositor::handleTouch(int eventType, const EmscriptenTouchEvent *touc
         touchPoint.id = touches->identifier;
         touchPoint.pressure = 1.0;
 
-        touchPoint.area.moveCenter(globalPoint);
+        touchPoint.area.moveCenter(targetPointInScreenCoords);
 
-        const auto tp = pressedTouchIds.constFind(touchPoint.id);
-        if (tp != pressedTouchIds.constEnd())
+        const auto tp = m_pressedTouchIds.constFind(touchPoint.id);
+        if (tp != m_pressedTouchIds.constEnd())
             touchPoint.normalPosition = tp.value();
 
-        QPointF localPoint = QPointF(window2->mapFromGlobal(globalPoint));
-        QPointF normalPosition(localPoint.x() / window2->width(),
-                               localPoint.y() / window2->height());
+        QPointF pointInTargetWindowCoords = QPointF(targetWindow->mapFromGlobal(targetPointInScreenCoords));
+        QPointF normalPosition(pointInTargetWindowCoords.x() / targetWindow->width(),
+                               pointInTargetWindowCoords.y() / targetWindow->height());
 
         const bool stationaryTouchPoint = (normalPosition == touchPoint.normalPosition);
         touchPoint.normalPosition = normalPosition;
 
         switch (eventType) {
             case EMSCRIPTEN_EVENT_TOUCHSTART:
-                if (tp != pressedTouchIds.constEnd()) {
+                if (tp != m_pressedTouchIds.constEnd()) {
                     touchPoint.state = (stationaryTouchPoint
                                         ? QEventPoint::State::Stationary
                                         : QEventPoint::State::Updated);
                 } else {
                     touchPoint.state = QEventPoint::State::Pressed;
                 }
-                pressedTouchIds.insert(touchPoint.id, touchPoint.normalPosition);
+                m_pressedTouchIds.insert(touchPoint.id, touchPoint.normalPosition);
 
                 break;
             case EMSCRIPTEN_EVENT_TOUCHEND:
                 touchPoint.state = QEventPoint::State::Released;
-                pressedTouchIds.remove(touchPoint.id);
+                m_pressedTouchIds.remove(touchPoint.id);
                 break;
             case EMSCRIPTEN_EVENT_TOUCHMOVE:
                 touchPoint.state = (stationaryTouchPoint
                                     ? QEventPoint::State::Stationary
                                     : QEventPoint::State::Updated);
 
-                pressedTouchIds.insert(touchPoint.id, touchPoint.normalPosition);
+                m_pressedTouchIds.insert(touchPoint.id, touchPoint.normalPosition);
                 break;
             default:
                 break;
@@ -1305,40 +1287,40 @@ int QWasmCompositor::handleTouch(int eventType, const EmscriptenTouchEvent *touc
         touchPointList.append(touchPoint);
     }
 
-    QFlags<Qt::KeyboardModifier> keyModifier = eventTranslator->translateTouchEventModifier(touchEvent);
+    QFlags<Qt::KeyboardModifier> keyModifier = m_eventTranslator->translateTouchEventModifier(touchEvent);
 
     bool accepted = false;
 
     if (eventType == EMSCRIPTEN_EVENT_TOUCHCANCEL)
-        accepted = QWindowSystemInterface::handleTouchCancelEvent(window2, QWasmIntegration::getTimestamp(), touchDevice, keyModifier);
+        accepted = QWindowSystemInterface::handleTouchCancelEvent(targetWindow, QWasmIntegration::getTimestamp(), m_touchDevice.get(), keyModifier);
     else
         accepted = QWindowSystemInterface::handleTouchEvent<QWindowSystemInterface::SynchronousDelivery>(
-                window2, QWasmIntegration::getTimestamp(), touchDevice, touchPointList, keyModifier);
+                targetWindow, QWasmIntegration::getTimestamp(), m_touchDevice.get(), touchPointList, keyModifier);
 
     return static_cast<int>(accepted);
 }
 
 void QWasmCompositor::leaveWindow(QWindow *window)
 {
-    windowUnderMouse = nullptr;
+    m_windowUnderMouse = nullptr;
     QWindowSystemInterface::handleLeaveEvent<QWindowSystemInterface::SynchronousDelivery>(window);
 }
 
-void QWasmCompositor::enterWindow(QWindow *window, const QPoint &localPoint, const QPoint &globalPoint)
+void QWasmCompositor::enterWindow(QWindow *window, const QPoint &pointInTargetWindowCoords, const QPoint &targetPointInScreenCoords)
 {
-    QWindowSystemInterface::handleEnterEvent<QWindowSystemInterface::SynchronousDelivery>(window, localPoint, globalPoint);
+    QWindowSystemInterface::handleEnterEvent<QWindowSystemInterface::SynchronousDelivery>(window, pointInTargetWindowCoords, targetPointInScreenCoords);
 }
 
 bool QWasmCompositor::processMouseEnter(const EmscriptenMouseEvent *mouseEvent)
 {
     Q_UNUSED(mouseEvent)
     // mouse has entered the canvas area
-    mouseInCanvas = true;
+    m_mouseInCanvas = true;
     return true;
 }
 
 bool QWasmCompositor::processMouseLeave()
 {
-    mouseInCanvas = false;
+    m_mouseInCanvas = false;
     return true;
 }
diff --git a/src/plugins/platforms/wasm/qwasmcompositor.h b/src/plugins/platforms/wasm/qwasmcompositor.h
index 29a0f02267..8524747a9d 100644
--- a/src/plugins/platforms/wasm/qwasmcompositor.h
+++ b/src/plugins/platforms/wasm/qwasmcompositor.h
@@ -146,7 +146,21 @@ private:
     void blit(QOpenGLTextureBlitter *blitter, QWasmScreen *screen, const QOpenGLTexture *texture, QRect targetGeometry);
 
     void drawWindowDecorations(QOpenGLTextureBlitter *blitter, QWasmScreen *screen, QWasmWindow *window);
-    void drwPanelButton();
+
+    static QPalette makeWindowPalette();
+
+    void drawFrameWindow(QWasmFrameOptions options, QPainter *painter);
+    void drawTitlebarWindow(QWasmTitleBarOptions options, QPainter *painter);
+    void drawShadePanel(QWasmTitleBarOptions options, QPainter *painter);
+    void drawItemPixmap(QPainter *painter, const QRect &rect,
+                                    int alignment, const QPixmap &pixmap) const;
+
+    static int keyboard_cb(int eventType, const EmscriptenKeyboardEvent *keyEvent, void *userData);
+    static int mouse_cb(int eventType, const EmscriptenMouseEvent *mouseEvent, void *userData);
+    static int focus_cb(int eventType, const EmscriptenFocusEvent *focusEvent, void *userData);
+    static int wheel_cb(int eventType, const EmscriptenWheelEvent *wheelEvent, void *userData);
+
+    static int touchCallback(int eventType, const EmscriptenTouchEvent *ev, void *userData);
 
     QScopedPointer<QOpenGLContext> m_context;
     QScopedPointer<QOpenGLTextureBlitter> m_blitter;
@@ -154,51 +168,35 @@ private:
     QHash<QWasmWindow *, QWasmCompositedWindow> m_compositedWindows;
     QList<QWasmWindow *> m_windowStack;
     QRegion m_globalDamage; // damage caused by expose, window close, etc.
-    bool m_needComposit;
-    bool m_inFlush;
-    bool m_inResize;
-    bool m_isEnabled;
+    bool m_needComposit = false;
+    bool m_inFlush = false;
+    bool m_inResize = false;
+    bool m_isEnabled = true;
     QSize m_targetSize;
-    qreal m_targetDevicePixelRatio;
+    qreal m_targetDevicePixelRatio = 1;
     QMap<QWasmWindow *, UpdateRequestDeliveryType> m_requestUpdateWindows;
     bool m_requestUpdateAllWindows = false;
     int m_requestAnimationFrameId = -1;
     bool m_inDeliverUpdateRequest = false;
 
-    QPointer<QWindow> draggedWindow;
-    QPointer<QWindow> pressedWindow;
-    QPointer<QWindow> lastWindow;
-    Qt::MouseButtons pressedButtons;
+    QPointer<QWindow> m_windowBeingManipulated;
+    QPointer<QWindow> m_pressedWindow;
+    QPointer<QWindow> m_lastMouseTargetWindow;
+    Qt::MouseButtons m_pressedButtons = Qt::NoButton;
 
-    QWasmCompositor::ResizeMode resizeMode;
-    QPoint resizePoint;
-    QRect resizeStartRect;
-    QPointingDevice *touchDevice;
+    ResizeMode m_resizeMode = ResizeNone;
+    QPoint m_resizePoint;
+    QRect m_resizeStartRect;
+    std::unique_ptr<QPointingDevice> m_touchDevice;
 
-    QMap <int, QPointF> pressedTouchIds;
+    QMap <int, QPointF> m_pressedTouchIds;
 
-    QCursor overriddenCursor;
-    bool isCursorOverridden = false;
-
-    static QPalette makeWindowPalette();
-
-    void drawFrameWindow(QWasmFrameOptions options, QPainter *painter);
-    void drawTitlebarWindow(QWasmTitleBarOptions options, QPainter *painter);
-    void drawShadePanel(QWasmTitleBarOptions options, QPainter *painter);
-    void drawItemPixmap(QPainter *painter, const QRect &rect,
-                                    int alignment, const QPixmap &pixmap) const;
-
-    static int keyboard_cb(int eventType, const EmscriptenKeyboardEvent *keyEvent, void *userData);
-    static int mouse_cb(int eventType, const EmscriptenMouseEvent *mouseEvent, void *userData);
-    static int focus_cb(int eventType, const EmscriptenFocusEvent *focusEvent, void *userData);
-    static int wheel_cb(int eventType, const EmscriptenWheelEvent *wheelEvent, void *userData);
-
-    static int touchCallback(int eventType, const EmscriptenTouchEvent *ev, void *userData);
+    bool m_isResizeCursorDisplayed = false;
 
-    QWasmEventTranslator *eventTranslator;
+    std::unique_ptr<QWasmEventTranslator> m_eventTranslator;
 
-    bool mouseInCanvas;
-    QPointer<QWindow> windowUnderMouse;
+    bool m_mouseInCanvas = false;
+    QPointer<QWindow> m_windowUnderMouse;
 };
 Q_DECLARE_OPERATORS_FOR_FLAGS(QWasmCompositor::SubControls)
 
diff --git a/src/plugins/platforms/wasm/qwasmcursor.cpp b/src/plugins/platforms/wasm/qwasmcursor.cpp
index f1f5e77bcb..f954e005ce 100644
--- a/src/plugins/platforms/wasm/qwasmcursor.cpp
+++ b/src/plugins/platforms/wasm/qwasmcursor.cpp
@@ -123,10 +123,10 @@ void QWasmCursor::setWasmCursor(QScreen *screen, const QByteArray &name)
     canvasStyle.set("cursor", val(name.constData()));
 }
 
-void QWasmCursor::setOverrideWasmCursor(QCursor *windowCursor, QScreen *screen)
+void QWasmCursor::setOverrideWasmCursor(const QCursor &windowCursor, QScreen *screen)
 {
     QWasmCursor *wCursor = static_cast<QWasmCursor *>(QWasmScreen::get(screen)->cursor());
-    wCursor->setWasmCursor(screen, wCursor->cursorShapeToHtml(windowCursor->shape()));
+    wCursor->setWasmCursor(screen, wCursor->cursorShapeToHtml(windowCursor.shape()));
 }
 
 void QWasmCursor::clearOverrideWasmCursor(QScreen *screen)
diff --git a/src/plugins/platforms/wasm/qwasmcursor.h b/src/plugins/platforms/wasm/qwasmcursor.h
index 17ddd344b1..4a5cb23bf4 100644
--- a/src/plugins/platforms/wasm/qwasmcursor.h
+++ b/src/plugins/platforms/wasm/qwasmcursor.h
@@ -13,7 +13,7 @@ public:
     void changeCursor(QCursor *windowCursor, QWindow *window) override;
 
     QByteArray cursorShapeToHtml(Qt::CursorShape shape);
-    static void setOverrideWasmCursor(QCursor *windowCursor, QScreen *screen);
+    static void setOverrideWasmCursor(const QCursor &windowCursor, QScreen *screen);
     static void clearOverrideWasmCursor(QScreen *screen);
 private:
     QByteArray htmlCursorName = "default";
diff --git a/src/plugins/platforms/wasm/qwasmeventtranslator.cpp b/src/plugins/platforms/wasm/qwasmeventtranslator.cpp
index 8f9050ba5d..6f13009aef 100644
--- a/src/plugins/platforms/wasm/qwasmeventtranslator.cpp
+++ b/src/plugins/platforms/wasm/qwasmeventtranslator.cpp
@@ -238,18 +238,6 @@ Qt::Key QWasmEventTranslator::translateEmscriptKey(const EmscriptenKeyboardEvent
     return qtKey;
 }
 
-Qt::MouseButton QWasmEventTranslator::translateMouseButton(unsigned short button)
-{
-    if (button == 0)
-        return Qt::LeftButton;
-    else if (button == 1)
-        return Qt::MiddleButton;
-    else if (button == 2)
-        return Qt::RightButton;
-
-    return Qt::NoButton;
-}
-
 struct KeyMapping { Qt::Key from, to; };
 
 constexpr KeyMapping tildeKeyTable[] = { // ~
diff --git a/src/plugins/platforms/wasm/qwasmeventtranslator.h b/src/plugins/platforms/wasm/qwasmeventtranslator.h
index d098c10b77..d86ddf7625 100644
--- a/src/plugins/platforms/wasm/qwasmeventtranslator.h
+++ b/src/plugins/platforms/wasm/qwasmeventtranslator.h
@@ -33,7 +33,18 @@ public:
     QFlags<Qt::KeyboardModifier> translateKeyboardEventModifier(const EmscriptenKeyboardEvent *keyEvent);
     QFlags<Qt::KeyboardModifier> translateMouseEventModifier(const EmscriptenMouseEvent *mouseEvent);
     QFlags<Qt::KeyboardModifier> translateTouchEventModifier(const EmscriptenTouchEvent *touchEvent);
-    static Qt::MouseButton translateMouseButton(unsigned short button);
+    static constexpr Qt::MouseButton translateMouseButton(unsigned short button) {
+        switch (button) {
+            case 0:
+                return Qt::LeftButton;
+            case 1:
+                return Qt::MiddleButton;
+            case 2:
+                return Qt::RightButton;
+            default:
+                return Qt::NoButton;
+        }
+    }
     static QCursor cursorForMode(QWasmCompositor::ResizeMode mode);
 
     QString getKeyText(const EmscriptenKeyboardEvent *keyEvent, Qt::Key key);
diff --git a/src/plugins/platforms/wasm/qwasmwindow.cpp b/src/plugins/platforms/wasm/qwasmwindow.cpp
index 171339fc6c..fbc1effb2c 100644
--- a/src/plugins/platforms/wasm/qwasmwindow.cpp
+++ b/src/plugins/platforms/wasm/qwasmwindow.cpp
@@ -229,8 +229,7 @@ QRegion QWasmWindow::resizeRegion() const
 
 bool QWasmWindow::isPointOnTitle(QPoint point) const
 {
-    bool ok = titleGeometry().contains(point);
-    return ok;
+    return hasTitleBar() ? titleGeometry().contains(point) : false;
 }
 
 bool QWasmWindow::isPointOnResizeRegion(QPoint point) const