Gestures and QGraphicsScene

[estel]

Hello,
I want to use gesture framework, but at the begining I have some problems.
I have QGraphicsView and QGraphicsScene
view->addScene(myScene);
At the myScene threre are few icons(QPixmapItem) . I try recognize QSwipeGesture( click somewhere on gaphicsScene and drag) and after recognizon start some animation (QtKinetic)
I have done:

view->grabGesture(Qt::SwipeGesture);

view->grabGesture(Qt::SwipeGesture);

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I had hoepe that event would propagate to QGraphicsScene and i have done in myScene

virtual bool myScene::event(QEvent *event)
	{
     if (event->type() == QEvent::Gesture)
        do something
     return QGraphicsScene::event(event);
	}

virtual bool myScene::event(QEvent *event)
	{
     if (event->type() == QEvent::Gesture)
        do something
     return QGraphicsScene::event(event);
	}

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unfortunaltely program does not go to line "do something".
What I do wrong??

[wysota]

First of all you should be grabbing the gesture on the view's viewport, not on the view itself.

[estel]

I modified my code. Now I run grab gestures on viewport and I try to catch QGesture event on object that inherits QGraphicsObject. Unfortunatelly it seems that there doesn't apper any gestureEvent. I have code everithing similar to example given by Qt.
I found the same problem in this and another forum, but there isn't any solve. So maybe is here anyone who menage to run application witch QGestures?

[stretchtiberius]

I have the same problem. I can get QGestureEvents from the Viewport but not from a QGraphicsObject. The just do not seem to be there. Anyone know why?

Here is a example of what I am trying.

class GestureTest : QGraphicsObject {
	Q_OBJECT
 
public:
 
	GestureTest() {
		grabGesture(Qt::PinchGesture);
	}
 
	bool sceneEvent(QEvent* pEvent) {
 
		if (pEvent->type() == QEvent::Gesture) {
			std::cout << "Gesture Received!" << std::endl;
		}
 
		return QGraphicsObject::sceneEvent(pEvent);
	}
};

class GestureTest : QGraphicsObject {
	Q_OBJECT

public:

	GestureTest() {
		grabGesture(Qt::PinchGesture);
	}

	bool sceneEvent(QEvent* pEvent) {

		if (pEvent->type() == QEvent::Gesture) {
			std::cout << "Gesture Received!" << std::endl;
		}

		return QGraphicsObject::sceneEvent(pEvent);
	}
};

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[wysota]

I would assume gesture events might not be propagated to items. It's still a new api in Qt, it might not be complete.

[stretchtiberius]

I would assume gesture events might not be propagated to items.

That could be the case. However, QGraphicsObject has a grabGesture() function. Therefore, there must be a way to make the gesture events propagate. Unless the planned API is not fully implemented.

[wysota]

Unless the planned API is not fully implemented.

That might be the case. Maybe you should try some Qt 4.7 snapshot.

[Luc4]

Sorry for disturbing, but I tried gesture recognition without success as well: is gesture classes only supported by some platforms or are all platforms supported?

[wysota]

That might be the case. Maybe you should try some Qt 4.7 snapshot.

The docs in 4.6 seem to suggest gestures work for graphic view's objects too.

[stretchtiberius]

is gesture classes only supported by some platforms or are all platforms supported?

From what I understand, multi-touch gestures are only supported on some platforms such as Windows 7.

The docs in 4.6 seem to suggest gestures work for graphic view's objects too.

That is what confuses me. I am using Qt 4.6.3 and yet I get no QGestureEvents from my QGraphicsObject.

Here is a full QGraphicsObject to test gestures with. Take a look and see if I am missing something. If someone else could test test it themselves that would be great! I just added it to a standard QGraphicsScene. I am compiling 4.7 beta now and will give that a try.

#ifndef ___TOUCHOBJECT___
#define ___TOUCHOBJECT___
 
#include <QtGui>
#include <iostream>
 
class TouchObject : public QGraphicsObject {
	Q_OBJECT
public:
	TouchObject(QGraphicsItem* pParent = NULL) : QGraphicsObject(pParent) {
		grabGesture(Qt::PinchGesture);
		grabGesture(Qt::PanGesture);
		grabGesture(Qt::SwipeGesture);
	}
 
	QRectF boundingRect() const {
		return QRectF(-WIDTH / 2, -HEIGHT / 2, WIDTH, HEIGHT);
	}
 
	QPainterPath shape() const {
		QPainterPath path;
		path.addEllipse(boundingRect());
		return path;
	}
 
	void paint(QPainter *painter, const QStyleOptionGraphicsItem *pOption, QWidget *pWidget) {
		pOption;
		pWidget;
		painter->setBrush(Qt::blue);
		painter->drawEllipse(boundingRect());
	}
 
	bool sceneEvent(QEvent* pEvent) {
			case QEvent::Gesture:
				std::cout << "Gesture Event Received from sceneEvent()" << std::endl;
		}
 
		return QGraphicsObject::sceneEvent(pEvent);
	}
 
	bool event(QEvent* pEvent) {
		switch (pEvent->type()) {
			case QEvent::Gesture:
				std::cout << "Gesture Event Received from event()" << std::endl;
		}
 
		return QGraphicsObject::event(pEvent);
	}
 
private:
	static const int WIDTH = 80;
	static const int HEIGHT = 80;
};
 
#endif

#ifndef ___TOUCHOBJECT___
#define ___TOUCHOBJECT___

#include <QtGui>
#include <iostream>

class TouchObject : public QGraphicsObject {
	Q_OBJECT
public:
	TouchObject(QGraphicsItem* pParent = NULL) : QGraphicsObject(pParent) {
		grabGesture(Qt::PinchGesture);
		grabGesture(Qt::PanGesture);
		grabGesture(Qt::SwipeGesture);
	}

	QRectF boundingRect() const {
		return QRectF(-WIDTH / 2, -HEIGHT / 2, WIDTH, HEIGHT);
	}

	QPainterPath shape() const {
		QPainterPath path;
		path.addEllipse(boundingRect());
		return path;
	}

	void paint(QPainter *painter, const QStyleOptionGraphicsItem *pOption, QWidget *pWidget) {
		pOption;
		pWidget;
		painter->setBrush(Qt::blue);
		painter->drawEllipse(boundingRect());
	}

	bool sceneEvent(QEvent* pEvent) {
			case QEvent::Gesture:
				std::cout << "Gesture Event Received from sceneEvent()" << std::endl;
		}

		return QGraphicsObject::sceneEvent(pEvent);
	}

	bool event(QEvent* pEvent) {
		switch (pEvent->type()) {
			case QEvent::Gesture:
				std::cout << "Gesture Event Received from event()" << std::endl;
		}

		return QGraphicsObject::event(pEvent);
	}

private:
	static const int WIDTH = 80;
	static const int HEIGHT = 80;
};

#endif

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[wysota]

Pan and swipe gestures don't require multi-touch.

[stretchtiberius]

I just tested using QGraphicObject with Qt 4.7.0 beta 1. Still did not work. I am beginning to think that this might be a complete oversight by the Qt developers. Maybe passing gesture events to a QGraphicsObject is unknowingly unfinished.