[Qt-interest] cannot grab gesture with qgraphicsobject

[Wathek LOUED]

Hi Till,

Thank you for your response I've already seen your bug post but unfortunatly
that doesn't help. Here are some part of my code :

*gesturerecognizer class :*
*
*
#ifndef GESTURERECOGNIZER_H
#define GESTURERECOGNIZER_H

#include "tapgesture.h"
#include "tapandholdgesture.h"

#include <QGestureRecognizer>
#include <QGesture>
#include <QEvent>
#include <QObject>
#include <QHash>

class TapGestureRecognizer: public QGestureRecognizer
{
public:
TapGestureRecognizer();
QGesture *create(QObject *target);
QGestureRecognizer::Result recognize(QGesture *state, QObject *watched,
QEvent *event);
void reset(QGesture *state);
private:
enum { TimerInterval = 400  };
enum { Delta = 20 };
QHash<long, TapGesture *> touchPoints;
};
#endif

#include "gesturerecognizer.h"

#include <QWidget>
#include <QTouchEvent>
#include <QDebug>
/*******************************************************
 * TapGesture Recognizer
 *******************************************************/
TapGestureRecognizer::TapGestureRecognizer()
{}

QGesture *TapGestureRecognizer::create(QObject *target)
{
if (target && target->isWidgetType())
static_cast<QWidget *>(target)->setAttribute(Qt::WA_AcceptTouchEvents);
return new TapGesture;
}

QGestureRecognizer::Result TapGestureRecognizer::recognize(QGesture *state,
QObject *, QEvent *event)
{
TapGesture *q = static_cast<TapGesture *>(state);
const QTouchEvent *ev = static_cast<const QTouchEvent *>(event);
QGestureRecognizer::Result result = QGestureRecognizer::CancelGesture;

switch (event->type()) {
case QEvent::TouchBegin: {
q->setPosition(ev->touchPoints().at(0).pos());
q->setHotSpot(ev->touchPoints().at(0).screenPos());
q->start();
result = QGestureRecognizer::MayBeGesture;
break;
}
case QEvent::TouchUpdate:
case QEvent::TouchEnd: {
if (ev->touchPoints().size() == 1) {
QTouchEvent::TouchPoint p = ev->touchPoints().at(0);
QPoint delta = p.pos().toPoint() - p.startPos().toPoint();
if (delta.manhattanLength() <= Delta && q->elapsed() <= TimerInterval &&
event->type() == QEvent::TouchEnd)
result = QGestureRecognizer::TriggerGesture;
else
result = QGestureRecognizer::CancelGesture;
}
break;
}
case QEvent::MouseButtonPress:
case QEvent::MouseMove:
case QEvent::MouseButtonRelease: {
result = QGestureRecognizer::Ignore;
break;
}
default: {
result = QGestureRecognizer::Ignore;
break;
}
}

return result;
}

void TapGestureRecognizer::reset(QGesture *state)
{
TapGesture *q = static_cast<TapGesture *>(state);
q->setPosition(QPointF());
QGestureRecognizer::reset(state);
}


*My QGraphicsView class :*
*
*
#ifndef FRMACCUEIL_H
#define FRMACCUEIL_H

#include "gesture/gesturerecognizer.h"

#include <QGraphicsView>
#include <QGraphicsScene>
#include <QGestureEvent>
#include <QEvent>
#include <QTouchEvent>
#include <QHash>

class FrmAccueil: public QGraphicsView
{
Q_OBJECT
public:
FrmAccueil(QGraphicsScene *scene=0, QWidget *parent=0);
bool viewportEvent(QEvent *event);

private:
void gestureEvent(QGestureEvent *event);
Qt::GestureType tapGesture;
TapGestureRecognizer *tapGestureRecognizer;
};

#endif

#include "frmaccueil.h"

#include <QDebug>
#include <QGestureRecognizer>

FrmAccueil::FrmAccueil(QGraphicsScene *scene, QWidget *parent)
   :QGraphicsView(scene, parent)
{
tapGestureRecognizer = new TapGestureRecognizer();

tapGesture = QGestureRecognizer::registerRecognizer(tapGestureRecognizer);

        viewport()->setAttribute(Qt::WA_AcceptTouchEvents);
viewport()->grabGesture(tapGesture);
}

bool FrmAccueil::viewportEvent(QEvent *event)
{
if (event->type() == QEvent::Gesture)
gestureEvent(static_cast<QGestureEvent*>(event));

return QGraphicsView::viewportEvent(event);
}

void FrmAccueil::gestureEvent(QGestureEvent *event)
{
if (event->gesture(tapGesture))
qDebug("TAP GESTURE");
}

*My QGraphicsScene class:*

#ifndef PUSHBUTTONITEM_H
#define PUSHBUTTONITEM_H

#include "gesture/gesturerecognizer.h"

#include <QGraphicsObject>
#include <QEvent>
#include <QGestureEvent>
#include <QPixmap>
#include <QPainter>

class PushButtonItem:public QGraphicsObject
{
Q_OBJECT
public:
enum ShapeMode {
MaskShape,
BoundingRectShape,
HeuristicMaskShape
};

PushButtonItem(QGraphicsItem *parent=0);
QPainterPath shape() const;

/* QGraphicsPixmapItem */
QPixmap pixmap() const;
void setPixmap(const QPixmap &pixmap);

Qt::TransformationMode transformationMode() const;
void setTransformationMode(Qt::TransformationMode transformation);

QRectF boundingRect() const;
 void paint(QPainter *painter, const QStyleOptionGraphicsItem *option,
QWidget *widget=0);

protected:
bool sceneEvent(QEvent *event);

private:
void gestureEvent(QGestureEvent *event);

ButtonType type;

QList<GraphicsLineItem *> edgeList;
TapGestureRecognizer *tapGestureRecognizer;
Qt::GestureType tapGesture;

// QGraphicsPixmapItem
QPixmap pix;
bool hasShape;
Qt::TransformationMode transfMode;
};

#endif

#include "pushbuttonitem.h"

#include <QPixmap>

#include <QDebug>
#include <QTouchEvent>
#include <QGestureRecognizer>

PushButtonItem::PushButtonItem(QGraphicsItem *parent)
       :QGraphicsObject(parent)
{
setFlags(QGraphicsItem::ItemIsMovable |
QGraphicsItem::ItemSendsGeometryChanges);

setTransformationMode(Qt::SmoothTransformation);
 setAcceptTouchEvents(true);

tapGestureRecognizer = new TapGestureRecognizer();
tapGesture = QGestureRecognizer::registerRecognizer(tapGestureRecognizer);

grabGesture(tapGesture);
}

QPainterPath PushButtonItem::shape() const
{ return QGraphicsItem::shape();     }

bool PushButtonItem::sceneEvent(QEvent *event)
{
qDebug("Event received");
if (event->type() == QEvent::Gesture)
gestureEvent(static_cast<QGestureEvent *>(event));
return true;

}

void PushButtonItem::gestureEvent(QGestureEvent *event)
{
if (event->gesture(tapGesture))
qDebug("button Tapped");
}

/***************************************************************
 * QGraphicsPixmapItem Reimplementation
 ***************************************************************/


I cannot really see where's the problem the QGraphicsView receive the
gestureEvent but not the QGraphicsObject.


Thank you so much

Sincerely
W.L

On Mon, Mar 7, 2011 at 11:02 PM, Till Oliver Knoll <
till.oliver.knoll at gmail.com> wrote:

> Am 07.03.11 19:31, schrieb Wathek LOUED:
>  > Hi,
>  >
>  > I got a problem with QGraphicsObject, I cannot grab gesture and I'm
>  > getting this message : QGestureManager::deliverEvent: could not find the
>  > target for gesture.
>
> My experience up to Qt 4.7.1 is that QGestures are not as "mature" as
> one would wish, especially on Mac.
>
> I had a somewhat similar issue that Pan gesture would not get through to
> QGraphicsObjects in a QGraphicsScene. It turned out that this is a
> "design issue" (how Gestures are implemented respective how items in a
> scene deal with events) and won't be fixed:
>
>   http://bugreports.qt.nokia.com/browse/QTBUG-16618
>
> There is an example attached which shows how gestures SHOULD work with
> QGraphicsObjects. Note that up to Qt 4.6.x also the QGraphicsView (the
> view widget thereof!) had to grab the same gestures as the item itself.
> This should not be necessary anymore with Qt 4.7.x.
>
> So in my case the QGraphicsObject did not receive Pan gesture events
> (only the "start" event, but never the "update" or "end" events). Never
> tried "Tab" events, but I got "pinch" (zoom/rotate) to work.
>
> But just now I am investigating another issue: it seems that the value of
>
>  http://doc.trolltech.com/4.7/qpinchgesture.html#scaleFactor-prop
>
> returns different signed values on Mac and Windows 7. I developped my
> app on Mac and implemented my "zoom" in such a way that when moving the
> fingers apart the object would get bigger.
>
> A quick test on some netbook and laptop running Windows 7 revealed that
> the "zoom" would work the other way (the object was scaled down instead
> of scaled up). So I assume it is the sign which is different on Mac and
> Windows 7 (= bug). But again, I did not have the opportunity yet to
> reproduce this behaviour with debugging possibilities.
>
>
> Hope that gives you some pointers,
>   Oliver
> _______________________________________________
> Qt-interest mailing list
> Qt-interest at qt.nokia.com
> http://lists.qt.nokia.com/mailman/listinfo/qt-interest
>
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