[Qt-interest] Drag and Drop when source is deleted

[Bo Thorsen]

Den 19-05-2011 17:54, Martin Grossberger skrev:
> Hello all,
>
> I have an issue with Drag&Drop, with which I hope you can help me:
> I have subclassed (twice) a QWidget and enabled dragging it. The widget
> also gets automatically deleted when an event hits.
> Now, if the widget gets deleted while I am dragging it, I can continue
> dragging, however once I drop it somewhere, the program crashes. The
> stacktrace from the debugger is:
> 0    QDrag::setMimeData    qdrag.cpp    145    0x047eb579
> 1    QDragManager::drag    qdnd_win.cpp    973    0x0484fa75
> 2    QDrag::start    qdrag.cpp    314    0x047eb8b6
> 3    MyCustomWidget::dragEvent    mycustomwidget.cpp    1285    0x0041ca80
> 4    MyWidget::mouseMoveEvent    mywidget.cpp    573    0x00526286
> 5    MyCustomWidget::mouseMoveEvent    mycustomwidget.cpp    1486
> 0x0041e814
> 6    QWidget::event    qwidget.cpp    7983    0x0482cee8
> 7    QApplicationPrivate::notify_helper    qapplication.cpp    4300
> 0x047e2520
> 8    QApplication::notify    qapplication.cpp    3865    0x047e0723
> 9    QCoreApplication::notifyInternal    qcoreapplication.cpp    704
> 0x6a1fd302
> 10    QCoreApplication::sendSpontaneousEvent    qcoreapplication.h
> 218    0x04e36eba
> 11    QApplicationPrivate::sendMouseEvent    qapplication.cpp    2963
> 0x047def40
> 12    QETWidget::translateMouseEvent    qapplication_win.cpp    3230
> 0x04847f10
> 13    QtWndProc at 16    qapplication_win.cpp    1623    0x0484309d
> 14    USER32!IsDialogMessageW    C:\Windows\syswow64\user32.dll    0
> 0x75fa6238
> 15    ??        0    0x00141dec
> 16    ??        0    0x00000200
> 17    USER32!AllowForegroundActivation
> C:\Windows\syswow64\user32.dll    0    0x75fa68ea
> 18    qt_is_translatable_mouse_event    qapplication_win.cpp    1395
> 0x04842675
> 19    USER32!GetMessageExtraInfo    C:\Windows\syswow64\user32.dll
> 0    0x75fa7d31
> 20    ??        0    0x00000000
> ...<Mehr>
>
> Is there something I can do to prevent the crash (other than deleting
> the widget)? Did I miss something?

It sounds like you are trying to drag the widget? If that's the case, 
you have to rewrite this. You have to drag only data, not active objects.

Bo Thorsen,
Fionia Software.

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