TouchBegin through childMouseEventFilter issue

Andrea Iuliano

Hi all.

I'm having an issue regarding input detection: the QEvent::TouchBegin comes from the mouse call

bool QQuickItem::childMouseEventFilter(QQuickItem *item, QEvent *event)

instead of the touch one

void QQuickItem::touchEvent(QTouchEvent *event)

Following the implementation details.

I've got two items, with parent-child hierarchy:

class MyRootWindowQML : public QQuickView {
public:
    MyRootWindowQML(QWindow* _wdw) : QQuickView(_wdw) {}
protected:
    bool event(QEvent *ev);
};

bool MyRootWindowQML::event(QEvent *ev) {
    QEvent::Type type = ev->type();

    if (type >= 194 && type <= 196)
        HCE::Logger(HCE::TEST_LEVEL, __PRETTY_FUNCTION__) << "touchType=" << type << std::endl;

    ...

    return QQuickView::event(ev);
}

class MyChildQQuickItem : public QQuickItem {
    Q_OBJECT

    ...
}

MyChildQQuickItem::MyChildQQuickItem(QQuickItem* parent) {
        ...
	QQuickItem::setParentItem( parent );
	QQuickItem::setPosition( QPointF(0.0, 0.0) );
	QQuickItem::setSize(QSizeF( parent->width(), parent->height()));
	QQuickItem::setFlag( QQuickItem::ItemHasContents );
	QQuickItem::setEnabled(true);
	QQuickItem::setAcceptedMouseButtons(Qt::AllButtons);
	QQuickItem::setAcceptHoverEvents(true);
	QQuickItem::setFiltersChildMouseEvents(true);
	QQuickItem::setAcceptTouchEvents(true);
}

The child one is the one who handles the input events and it exposes the methods to do it:

bool MyChildQQuickItem::childMouseEventFilter(QQuickItem *item, QEvent *event) {
	switch( event->type() ){
		case QEvent::MouseButtonPress:
			mousePressEvent(static_cast<QMouseEvent*>(event));
			break;
		case QEvent::MouseMove:
			mouseMoveEvent(static_cast<QMouseEvent*>(event));
			break;
		case QEvent::MouseButtonRelease:
			mouseReleaseEvent(static_cast<QMouseEvent*>(event));
			break;
		case QEvent::MouseButtonDblClick:
			mouseDoubleClickEvent(static_cast<QMouseEvent*>(event));
			break;
		case QEvent::TouchBegin:
		case QEvent::TouchUpdate:
		case QEvent::TouchEnd:
		case QEvent::TouchCancel:
        	HCE::Logger(HCE::WARNING_LEVEL, __PRETTY_FUNCTION__) << "TouchEvent comes from childMouseEventFilter: touchType=" << event->type() << std::endl;
			touchEvent(static_cast<QTouchEvent*>(event)); //My workaround
			break;
		default:
        	HCE::Logger(HCE::ERROR_LEVEL, __PRETTY_FUNCTION__) << "Uknown mouse event receved: eventType=" << event->type() << std::endl;
	}
	return true;
}


void MyChildQQuickItem::mousePressEvent(QMouseEvent *event){
	HCE::Logger(HCE::TEST_LEVEL, __PRETTY_FUNCTION__) << "touchType=" << event->type() << std::endl;
	...
}


void MyChildQQuickItem::mouseMoveEvent(QMouseEvent *event){
	HCE::Logger(HCE::TEST_LEVEL, __PRETTY_FUNCTION__) << "touchType=" << event->type() << std::endl;
	...
}

void MyChildQQuickItem::mouseReleaseEvent(QMouseEvent *event){
	HCE::Logger(HCE::TEST_LEVEL, __PRETTY_FUNCTION__) << "touchType=" << event->type() << std::endl;
	...
}

void MyChildQQuickItem::wheelEvent(QWheelEvent *event){
	HCE::Logger(HCE::TEST_LEVEL, __PRETTY_FUNCTION__) << "touchType=" << event->type() << std::endl;
	...
}

void MyChildQQuickItem::touchEvent(QTouchEvent *event){
	HCE::Logger(HCE::TEST_LEVEL, __PRETTY_FUNCTION__) << "touchType=" << event->type() << std::endl;
	...
}

void MyChildQQuickItem::hoverMoveEvent(QHoverEvent *event){
	HCE::Logger(HCE::TEST_LEVEL, __PRETTY_FUNCTION__) << "touchType=" << event->type() << std::endl;
	...
}

As you can see from the following log, I am receiving the TouchBegin event into childMouseEventFilter function, instead of touchEvent one, where I've correctly received TouchUpdate and TouchEnd.

[TEST     ] 10/06/2019-07:21:06.247906 (7FCE03EB5A40) virtual bool MyRootWindowQML::event(QEvent*): touchType=194
[WARNING  ] 10/06/2019-07:21:06.248955 (7FCE03EB5A40) virtual bool MyChildQQuickItem::childMouseEventFilter(QQuickItem*, QEvent*): TouchEvent comes from childMouseEventFilter: touchType=194
[TEST     ] 10/06/2019-07:21:06.258322 (7FCE03EB5A40) virtual bool MyRootWindowQML::event(QEvent*): touchType=195
[TEST     ] 10/06/2019-07:21:06.260517 (7FCE03EB5A40) virtual void MyChildQQuickItem::touchEvent(QTouchEvent*): touchType=195
[TEST     ] 10/06/2019-07:21:06.269321 (7FCE03EB5A40) virtual bool MyRootWindowQML::event(QEvent*): touchType=195
[TEST     ] 10/06/2019-07:21:06.271481 (7FCE03EB5A40) virtual void MyChildQQuickItem::touchEvent(QTouchEvent*): touchType=195
[TEST     ] 10/06/2019-07:21:06.282024 (7FCE03EB5A40) virtual bool MyRootWindowQML::event(QEvent*): touchType=195
[TEST     ] 10/06/2019-07:21:06.287264 (7FCE03EB5A40) virtual void MyChildQQuickItem::touchEvent(QTouchEvent*): touchType=195
[TEST     ] 10/06/2019-07:21:06.298108 (7FCE03EB5A40) virtual bool MyRootWindowQML::event(QEvent*): touchType=195
[TEST     ] 10/06/2019-07:21:06.303338 (7FCE03EB5A40) virtual void MyChildQQuickItem::touchEvent(QTouchEvent*): touchType=195
[TEST     ] 10/06/2019-07:21:06.314658 (7FCE03EB5A40) virtual bool MyRootWindowQML::event(QEvent*): touchType=195
[TEST     ] 10/06/2019-07:21:06.319867 (7FCE03EB5A40) virtual void MyChildQQuickItem::touchEvent(QTouchEvent*): touchType=195
[TEST     ] 10/06/2019-07:21:06.336220 (7FCE03EB5A40) virtual bool MyRootWindowQML::event(QEvent*): touchType=195
[TEST     ] 10/06/2019-07:21:06.336295 (7FCE03EB5A40) virtual void MyChildQQuickItem::touchEvent(QTouchEvent*): touchType=195
[TEST     ] 10/06/2019-07:21:06.348019 (7FCE03EB5A40) virtual bool MyRootWindowQML::event(QEvent*): touchType=196
[TEST     ] 10/06/2019-07:21:06.348074 (7FCE03EB5A40) virtual void MyChildQQuickItem::touchEvent(QTouchEvent*): touchType=196

By the documentation (https://doc.qt.io/qt-5/qquickitem.html#childMouseEventFilter), the method childMouseEventFilter should handle only mouse events.

How can I fix it?

Thank you.

Andrea