Details

Type: Bug
Resolution: Unresolved
Priority: P2: Important
Fix Version/s: None
Affects Version/s: 5.15.14, 6.5.0
Component/s: GUI: Basic Input System (keyboard, mouse, touch), QPA: Wayland, Quick: Core Declarative QML
Labels:
None

Platform/s:

Linux/Wayland

Description

This bug is like in the attached video，can be reproduced like this

Reproduced

1. Setting a MouseArea in window, and set the cursorShape

Window {
    width: 640
    height: 480
    visible: true
    title: qsTr("Hello World")   
        Rectangle{
            width: 100
            height: 100
            color: "red"
            MouseArea{
                anchors.fill:parent
                cursorShape: Qt.BusyCursor
            }
        }
    
}

2. Put the mouse in the window before the window starts, when the window opens, the mouse will change to the shape set at (0, 0) coordinates

Analyze

Root case：

The static method QCursor:pos() will read the `mLastPos` in QWaylandCursor. It is only updated when the MouseEvent occurs. When entering for the first time, only enter event, so its value is the default {0,0}. At {0,0}, the mouse is set to a new shape, so it appears made a mistake

Related code：

in qtdeclarative/src/quick/items/qquickwindow.cpp, it use QCursor:pos() to updateCursor

    case QEvent::Enter: {
        if (!d->contentItem)
            return false;
        QEnterEvent *enter = static_cast<QEnterEvent*>(e);
        bool accepted = enter->isAccepted();
        bool delivered = d->deliverHoverEvent(d->contentItem, enter->windowPos(), d->lastMousePosition,
            QGuiApplication::keyboardModifiers(), 0L, accepted);
        d->lastMousePosition = enter->windowPos();
        enter->setAccepted(accepted);
#if QT_CONFIG(cursor)
         
        d->updateCursor(mapFromGlobal(QCursor::pos()));
#endif
        return delivered;

final read the property, and it's just be changed in QWaylandCursor::pointerEvent

QPoint QWaylandCursor::pos() const
{
    return mLastPos;
}

void QWaylandCursor::pointerEvent(const QMouseEvent &event)
{
    mLastPos = event.globalPos();
}

And the pointerEvent is only called in MouseEvent `cursor->pointerEvent(ev)`

void QGuiApplicationPrivate::processMouseEvent(QWindowSystemInterfacePrivate::MouseEvent *e){
````````
#ifndef QT_NO_CURSOR
    if (!e->synthetic()) {
        if (const QScreen *screen = window->screen())
            if (QPlatformCursor *cursor = screen->handle()->cursor()) {
                const QPointF nativeLocalPoint = QHighDpi::toNativePixels(localPoint, screen);
                const QPointF nativeGlobalPoint = QHighDpi::toNativePixels(globalPoint, screen);
                QMouseEvent ev(type, nativeLocalPoint, nativeLocalPoint, nativeGlobalPoint,
                                          button, e->buttons, e->modifiers, e->source);
                ev.setTimestamp(e->timestamp);
                cursor->pointerEvent(ev);
            }
    }
#endif
``````

Due to the fact that the enter event does not trigger a MouseEvent, it will not be called here. The issue is caused by the default value of mLastPos being {0,0}.

I attempted to solve the issue by handling the MouseEvent in advance in the enter event of QtWayland, but I am not sure if this is a reasonable approach.

void QWaylandWindow::handleMouse(QWaylandInputDevice *inputDevice, const QWaylandPointerEvent &e)
{

    if (mWindowDecoration) {
        handleMouseEventWithDecoration(inputDevice, e);
    } else {
        switch (e.type) {
            case QEvent::Enter:
                // ADD
                QWindowSystemInterface::handleMouseEvent(window(), e.timestamp, e.local, e.global, e.buttons, e.button, e.type, e.modifiers);
                QWindowSystemInterface::handleEnterEvent(window(), e.local, e.global);
                break;

By the way, this issue was not reproduced on x11 because they retrieve the position of the coordinates in real time.

// qtbase/src/plugins/platforms/xcb/qxcbcursor.cpp

QPoint QXcbCursor::pos() const
{
    QPoint p;
    queryPointer(connection(), nullptr, &p);
    return p;
}


void QXcbCursor::queryPointer(QXcbConnection *c, QXcbVirtualDesktop **virtualDesktop, QPoint *pos, int *keybMask)
{
    if (pos)
        *pos = QPoint();

    xcb_window_t root = c->primaryVirtualDesktop()->root();

    auto reply = Q_XCB_REPLY(xcb_query_pointer, c->xcb_connection(), root);
    if (reply) {
        if (virtualDesktop) {
            const auto virtualDesktops = c->virtualDesktops();
            for (QXcbVirtualDesktop *vd : virtualDesktops) {
                if (vd->root() == reply->root) {
                    *virtualDesktop = vd;
                    break;
                }
            }
        }
        if (pos)
            *pos = QPoint(reply->root_x, reply->root_y);
        if (keybMask)
            *keybMask = reply->mask;
        return;
    }
}