QCustomPlot and multitouch zoom

[Franckynos]

Hi everybody.

I use QCustomPlot library and I would like use my application on tablet.
But I have some trouble to interact with 2 touchs for zoom.

I try to write this:

bool CustomPlot::event(QEvent* event)
{
if(event->type() == QEvent::TouchBegin ||
event->type() == QEvent::TouchUpdate ||
event->type() == QEvent::TouchEnd ){
QTouchEvent *touchEvent = static_cast<QTouchEvent *>(event);
QListQTouchEvent::TouchPoint touchPoints = touchEvent->touchPoints();

    if(touchPoints.count() == 1 && touchEvent->touchPointStates().testFlag(Qt::TouchPointReleased))
        _release2touch = false;

    if (touchPoints.count() == 1 && !_release2touch)
    {
        switch (event->type()) {
        case QEvent::TouchBegin:
        {
            QTouchEvent *touchEvent = static_cast<QTouchEvent *>(event);
            QTouchEvent::TouchPoint touchPoints = touchEvent->touchPoints().first();
            QMouseEvent *e = new QMouseEvent(QEvent::MouseButtonPress,
                                             touchPoints.pos(), Qt::LeftButton, Qt::LeftButton, Qt::NoModifier);

            emit mousePressEvent(e);
            return true;

        }break;

        case QEvent::TouchUpdate:
        {
            QTouchEvent *touchEvent = static_cast<QTouchEvent *>(event);
            QTouchEvent::TouchPoint touchPoints = touchEvent->touchPoints().first();
            QMouseEvent *e = new QMouseEvent(QEvent::MouseMove,
                                             touchPoints.pos(), Qt::LeftButton, Qt::LeftButton, Qt::NoModifier);

            emit mouseMoveEvent(e);
            return true;

        }break;

        case QEvent::TouchEnd:{
            QTouchEvent *touchEvent = static_cast<QTouchEvent *>(event);
            QTouchEvent::TouchPoint touchPoints = touchEvent->touchPoints().first();
            QMouseEvent *e = new QMouseEvent(QEvent::MouseButtonRelease,
                                             touchPoints.pos(), Qt::LeftButton, Qt::LeftButton, Qt::NoModifier);

            emit mouseReleaseEvent(e);
            return true;

        }break;

        default:
            return false;
            break;
        }
    }else if (touchPoints.count() == 2) {
        _release2touch = true;
        // determine scale factor
        const QTouchEvent::TouchPoint &touchPoint0 = touchPoints.first();
        const QTouchEvent::TouchPoint &touchPoint1 = touchPoints.last();
        double currentScaleFactor =
                QLineF(touchPoint0.pos(), touchPoint1.pos()).length() /
                QLineF(touchPoint0.lastPos(), touchPoint1.lastPos()).length();

        QPointF centreZoom = QPointF((touchPoint0.pos().x()+ touchPoint1.pos().x())/2 ,
                                     (touchPoint0.pos().y()+ touchPoint1.pos().y())/2);
        QPointF lastCenterZoom = QPointF((touchPoint0.lastPos().x()+ touchPoint1.lastPos().x())/2 ,
                                         (touchPoint0.lastPos().y()+ touchPoint1.lastPos().y())/2);

        if (touchEvent->touchPointStates().testFlag(Qt::TouchPointReleased))
            currentScaleFactor = 1;

        if(currentScaleFactor<1)
            currentScaleFactor = currentScaleFactor + (1-currentScaleFactor)/8;
        else
            currentScaleFactor = currentScaleFactor+(currentScaleFactor-1)/8;

        currentScaleFactor =1/currentScaleFactor;

        double diffX = this->xAxis->pixelToCoord(lastCenterZoom.x())
                - this->xAxis->pixelToCoord(centreZoom.x());

        double diffY = this->yAxis->pixelToCoord(lastCenterZoom.y())
                - this->yAxis->pixelToCoord(centreZoom.y());

        if(!touchEvent->touchPointStates().testFlag(Qt::TouchPointReleased)){
            this->xAxis->moveRange(diffX);
            this->yAxis->moveRange(diffY);
            this->xAxis->scaleRange(currentScaleFactor,this->xAxis->pixelToCoord(centreZoom.x()));
            this->yAxis->scaleRange(currentScaleFactor,this->yAxis->pixelToCoord(centreZoom.y()));
            this->replot();
        }
        return true;
    }
}else{
    return QWidget::event(event);
}
return false;  // a ajouter ?

}

When I was in 32 bits on Qt 5.2 this code works fine...
I upgrade my code to 64 bits with Qt 5.4, and I have some trouble, the interaction is not running fluid.

Someone can hlep me ? I'm not sure with my methode?

[SGaist]

Hi,

The change of architecture should not have any influence on the matter but you might be hitting a regression. What difference are you seeing ?

[Franckynos]

@SGaist Hi, I think is come from Windows 8.
My tablet run under windows 8.1 and simulate the touch point by mouse action. I have make some modification like that :

if(_touchDevice)
{
if(event->type() == QEvent::MouseButtonDblClick ||
event->type() == QEvent::MouseButtonPress ||
event->type() == QEvent::MouseButtonRelease ||
event->type() == QEvent::MouseMove ||
event->type() == QEvent::MouseTrackingChange)
{
event->ignore();
return true;
}
}

And with this, it work very well and it's fluid. But now it doesn't work on PC ... Because I block mouse even .

[SGaist]

You should take a look at the bug report system to see if it's something known

[vishnu]

@Franckynos @SGaist
Hello,
I have used your function. I got these errors...

1. _release2touch was not declared in this scope...I hope it is of type bool ,so i have declared a member variable bool release2touch. May i know the use of it?
2. error: cannot call member function 'virtual bool QWidget::event(QEvent*)' without object
   return QWidget::event(event); ....At the return statement it is there...What should i do to remove this error?
3. How should i make use of this function ? I mean when does this function is called ?How can I call this function esp from QML if you don't know qml atleast give me an example in C+++.thanks a lot.

[Franckynos]

@vishnu said:

May i know the use of it?

1. yes it's a bool at false in constructor
2. you have forget event in prototype :
   'virtual bool QWidget::event(QEvent*)' without object in => 'virtual bool QWidget::event(QEvent* !!! event !!! )' without object

CustomPlot::CustomPlot(QWidget *parent)
    :QCustomPlot(parent)
{
    setAttribute(Qt::WA_AcceptTouchEvents);
    _release2touch = false;
    _touchDevice = false;
}

bool CustomPlot::event(QEvent* event)
{
    if(_touchDevice)
    {
        if(event->type() == QEvent::MouseButtonDblClick ||
                event->type() == QEvent::MouseButtonPress ||
                event->type() == QEvent::MouseButtonRelease ||
                event->type() == QEvent::MouseMove ||
                event->type() == QEvent::MouseTrackingChange)
        {
            event->ignore();
            return true;
        }

        if(event->type() == QEvent::Wheel)
            _touchDevice = false;
    }

    if(event->type() == QEvent::TouchBegin ||
            event->type() == QEvent::TouchUpdate ||
            event->type() == QEvent::TouchEnd ){

        if(!_touchDevice)
            _touchDevice = true;

        QTouchEvent *touchEvent = static_cast<QTouchEvent *>(event);
        QList<QTouchEvent::TouchPoint> touchPoints = touchEvent->touchPoints();

        if(touchPoints.count() == 1 && touchEvent->touchPointStates().testFlag(Qt::TouchPointReleased))
            _release2touch = false;

        if (touchPoints.count() == 1 && !_release2touch)
        {
            switch (event->type()) {
            case QEvent::TouchBegin:
            {
                QTouchEvent *touchEvent = static_cast<QTouchEvent *>(event);
                QTouchEvent::TouchPoint touchPoints = touchEvent->touchPoints().first();
                QMouseEvent *e = new QMouseEvent(QEvent::MouseButtonPress,
                                                 touchPoints.pos(), Qt::LeftButton, Qt::LeftButton, Qt::NoModifier);

                mousePressEvent(e); //==> meilleure methode
            }break;

            case QEvent::TouchUpdate:
            {
                QTouchEvent *touchEvent = static_cast<QTouchEvent *>(event);
                QTouchEvent::TouchPoint touchPoints = touchEvent->touchPoints().first();
                QMouseEvent *e = new QMouseEvent(QEvent::MouseMove,
                                                 touchPoints.pos(), Qt::LeftButton, Qt::LeftButton, Qt::NoModifier);

                mouseMoveEvent(e);
            }break;

            case QEvent::TouchEnd:{
                QTouchEvent *touchEvent = static_cast<QTouchEvent *>(event);
                QTouchEvent::TouchPoint touchPoints = touchEvent->touchPoints().first();
                QMouseEvent *e = new QMouseEvent(QEvent::MouseButtonRelease,
                                                 touchPoints.pos(), Qt::LeftButton, Qt::LeftButton, Qt::NoModifier);

                mouseReleaseEvent(e);
            }break;

            default:
                break;
            }
        }else if (touchPoints.count() == 2) {
            _release2touch = true;
            // determine scale factor
            const QTouchEvent::TouchPoint &touchPoint0 = touchPoints.first();
            const QTouchEvent::TouchPoint &touchPoint1 = touchPoints.last();//   touchPoints.last();

            double currentScaleFactor =
                    QLineF(touchPoint0.pos(), touchPoint1.pos()).length() /
                    QLineF(touchPoint0.lastPos(), touchPoint1.lastPos()).length();

            QPointF centreZoom = QPointF((touchPoint0.pos().x()+ touchPoint1.pos().x())/2 ,
                                         (touchPoint0.pos().y()+ touchPoint1.pos().y())/2);
            QPointF lastCenterZoom = QPointF((touchPoint0.lastPos().x()+ touchPoint1.lastPos().x())/2 ,
                                             (touchPoint0.lastPos().y()+ touchPoint1.lastPos().y())/2);

            if (touchEvent->touchPointStates().testFlag(Qt::TouchPointReleased))
                currentScaleFactor = 1;


            if(currentScaleFactor<1)
                currentScaleFactor = currentScaleFactor + (1-currentScaleFactor)/8;
            else
                currentScaleFactor = currentScaleFactor+ (currentScaleFactor-1)/8;

            currentScaleFactor =1/currentScaleFactor;

            double diffX = this->xAxis->pixelToCoord(lastCenterZoom.x())
                    - this->xAxis->pixelToCoord(centreZoom.x());

            double diffY = this->yAxis->pixelToCoord(lastCenterZoom.y())
                    - this->yAxis->pixelToCoord(centreZoom.y());

            if(!touchEvent->touchPointStates().testFlag(Qt::TouchPointReleased)){
                this->xAxis->moveRange(diffX);
                this->yAxis->moveRange(diffY);
                this->xAxis->scaleRange(currentScaleFactor,this->xAxis->pixelToCoord(centreZoom.x()));
                this->yAxis->scaleRange(currentScaleFactor,this->yAxis->pixelToCoord(centreZoom.y()));
                this->replot();
            }
        }
        return true;
    }
    return QWidget::event(event);
}