Is it possible to drag an item of a QComboBox?

[jjcarles]

Hi.

I'm trying to create a class that allows me to drag & drop items from a QComboBox.

class IndicatorComboBox : public QComboBox
{
    Q_OBJECT
 
protected:
    QPoint m_dragStartPosition;
 
    void mousePressEvent(QMouseEvent *pEvent);
    void mouseMoveEvent(QMouseEvent *pEvent);
 
public:
    IndicatorComboBox(QWidget *parent = 0);
 
signals:
 
public slots:
 
}

class IndicatorComboBox : public QComboBox
{
    Q_OBJECT

protected:
    QPoint m_dragStartPosition;

    void mousePressEvent(QMouseEvent *pEvent);
    void mouseMoveEvent(QMouseEvent *pEvent);

public:
    IndicatorComboBox(QWidget *parent = 0);

signals:

public slots:

}

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IndicatorComboBox::IndicatorComboBox(QWidget *parent) : QComboBox(parent)
{
}
 
void IndicatorComboBox::mousePressEvent(QMouseEvent *pEvent)
{
    if (pEvent->button() == Qt::LeftButton) {
        m_dragStartPosition = pEvent->pos();
    }
 
    QComboBox::mousePressEvent(pEvent);    
}
 
void IndicatorComboBox::mouseMoveEvent(QMouseEvent *pEvent)
{
    if (!(pEvent->buttons() & Qt::LeftButton)) {
        return;
    }
 
    if (currentIndex() < 0) {
        return;
    }
 
    if ((pEvent->pos() - m_dragStartPosition).manhattanLength() < QApplication::startDragDistance()) {
        return;
    }
 
    QDrag *drag = new QDrag(this);
    QMimeData *mimeData = new QMimeData;
 
    mimeData->setText(currentText());
    drag->setMimeData(mimeData);
 
    //drag->start();
    Qt::DropAction dropAction = drag->exec(Qt::CopyAction | Qt::MoveAction);
}

IndicatorComboBox::IndicatorComboBox(QWidget *parent) : QComboBox(parent)
{
}

void IndicatorComboBox::mousePressEvent(QMouseEvent *pEvent)
{
    if (pEvent->button() == Qt::LeftButton) {
        m_dragStartPosition = pEvent->pos();
    }
    
    QComboBox::mousePressEvent(pEvent);    
}

void IndicatorComboBox::mouseMoveEvent(QMouseEvent *pEvent)
{
    if (!(pEvent->buttons() & Qt::LeftButton)) {
        return;
    }

    if (currentIndex() < 0) {
        return;
    }

    if ((pEvent->pos() - m_dragStartPosition).manhattanLength() < QApplication::startDragDistance()) {
        return;
    }

    QDrag *drag = new QDrag(this);
    QMimeData *mimeData = new QMimeData;

    mimeData->setText(currentText());
    drag->setMimeData(mimeData);

    //drag->start();
    Qt::DropAction dropAction = drag->exec(Qt::CopyAction | Qt::MoveAction);
}

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My problem is that if there is the line "QComboBox::mousePressEvent(pEvent); " I can't drag the items. And, if I remove the line, the combobox will not open (but the drag works fine).

Thanks in advance.

[wysota]

Did you think about calling the base class implementation of the mouseMoveEvent as well?

[jjcarles]

Thanks for responding. I had not thought calling the base class implementation of the "mouseMoveEvent". I tried your idea, but has not worked.. I think the problem is in the event "mousePressEvent" but I don't know how to solve it. Or QComboBox works or works drag & drop, but not both. Any idea?