No drag target set ?

Nevez

MainWindow(0x550db4f6b0, name="MainWindow") : No drag target set.

Sometimes it gives this error when I drop a widget in a custom area set. I've looked on the net but couldn't find any documentation that directly explains this error.
Why am I getting this error?

SGaist

Hi,

How did you implement drag and drop ?

Nevez

Hello, of course, if we briefly summarize the code;
This is how I initiate a drag when the widget is clicked.

if(widget == Q_NULLPTR)
        return;
    QByteArray byteArray(reinterpret_cast<char*>(&widget),sizeof(QWidget*));
    QDrag *drag = new QDrag(this);
    QMimeData * mimeData = new QMimeData;
    mimeData->setData("Label",byteArray);
    drag->setMimeData(mimeData);
    QPoint globalPos = mapToGlobal(pos);
    QPoint p = widget->mapFromGlobal(globalPos);
    drag->setHotSpot(p);
    drag->setPixmap(widget->grab());
    drag->exec(Qt::CopyAction | Qt::MoveAction);

then I use dragenterevent and dropevent functions in the widget I will carry.
DropEvent:

if(event->mimeData()->hasFormat("Label") )   // in listwidget class
    {
        event->acceptProposedAction();
        QByteArray byteArray = event->mimeData()->data("Label");
        QWidget * widget = *reinterpret_cast<QWidget**>(byteArray.data());
        KrnLabel * new_label =  qobject_cast<KrnLabel *>(widget);
           
            QListWidgetItem *item = new QListWidgetItem();
            QSize size = QSize(new_label->sizeHint().width()+15,new_label->sizeHint().height());
            item->setSizeHint(size);
 
            addItem(item);
            setItemWidget(item,new_label );
          
        

    }
    else
        event->ignore();
}

It doesn't always give this error. It only happens at certain times. For example, when I drag 7-8 widgets, I only get this error on one of them.
Why am I getting this error randomly?

SGaist

The implementation itself does not look wrong although I wouldn't move pointers to widget pointers around.

Nevez

@SGaist said in No drag target set ?:

The implementation itself does not look wrong although I wouldn't move pointers to widget pointers around.

could this be a bug?

SGaist

I have a doubt that this is a bug.

Can you provide a minimal compilable example that reliably shows this message ?

By the way, which version of Qt are you using ?
On which platform ?