Details
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Bug
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Resolution: Unresolved
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P2: Important
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None
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5.5.1
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None
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Windows 8.1, VS2015, Qt 5.5.1 (Snapshot 153)
Description
This is not necessarily a bug as we're doing stuff that QtQuick isn't designed for, but I thought I'd bring it up anyway.
We do our own handling of drag/drop events as the current QtQuick implementation was/is full of blocker bugs (i.e. stickyness of the active property / dropping mimeData is problematic - https://bugreports.qt.io/browse/QTBUG-40773)
We essentially have the a qquickwidget inside a tabwidget (similar to a word processor setup). From a mousearea inside the quickwidget we handle the mouse press/move/release/enter/exit and send it to C++). On a text drag we start our own QDrag(). Unfortunately as this is an invokable, it's started in the QML thread. A user then pressed ctrl+w to close the current document (while still holding the mouse button down for the drag), which was handled as a global shortcut event. This was processed and the tab was closed and deleted (and the quickwidget->DeleteLater()). The QQuickWidget was therefore deleted while still waiting the QDrag to finish and died.
The assert is:
ASSERT: "context() && engine()" in file qml\qqmlboundsignal.cpp, line 183
The stack is as follows:
0 NtUserWaitMessage USER32 0x7ffbeec0104a 1 DialogBox2 USER32 0x7ffbeec35bc7 2 InternalDialogBox USER32 0x7ffbeec37732 3 SoftModalMessageBox USER32 0x7ffbeec399f2 4 MessageBoxWorker USER32 0x7ffbeec3918d 5 MessageBoxTimeoutW USER32 0x7ffbeec8812a 6 MessageBoxW USER32 0x7ffbeec8819e 7 __crtMessageBoxW crtmbox.c 250 0x7ffbbb017509 8 __crtMessageWindowW dbgrpt.c 391 0x7ffbbb00be1b 9 _VCrtDbgReportW dbgrptt.c 672 0x7ffbbb016b36 10 _CrtDbgReportWV dbgrpt.c 263 0x7ffbbb00b3b0 11 _CrtDbgReportW dbgrpt.c 279 0x7ffbbb00b340 12 qt_message_fatal qlogging.cpp 1567 0x6ee8a57a 13 QMessageLogger::fatal qlogging.cpp 781 0x6ee88de6 14 qt_assert qglobal.cpp 2967 0x6ee7e422 15 QQmlBoundSignalExpression::function qqmlboundsignal.cpp 183 0x69bdc005 16 QQmlBoundSignalExpression::sourceLocation qqmlboundsignal.cpp 155 0x69bdbcfd 17 QQmlData::destroyed qqmlengine.cpp 1710 0x69b9f06f 18 QQmlData::destroyed qqmlengine.cpp 675 0x69b9e907 19 QObject::~QObject qobject.cpp 917 0x6f28d2a9 20 QQuickItem::~QQuickItem qquickitem.cpp 2289 0x7ffbba88c43a 21 QQuickMouseArea::~QQuickMouseArea qquickmousearea.cpp 441 0x7ffbba99e6b2 22 QQmlPrivate::QQmlElement<QQuickMouseArea>::~QQmlElement<QQuickMouseArea> qqmlprivate.h 98 0x7ffbba915e2d 23 QQmlPrivate::QQmlElement<QQuickMouseArea>::`scalar deleting destructor' Qt5Quickd 0x7ffbba917d57 24 QObjectPrivate::deleteChildren qobject.cpp 1946 0x6f2935d6 25 QObject::~QObject qobject.cpp 1026 0x6f28d7c0 26 QQuickItem::~QQuickItem qquickitem.cpp 2289 0x7ffbba88c43a 27 QQuickRectangle::~QQuickRectangle Qt5Quickd 0x7ffbba8b8193 28 QQmlPrivate::QQmlElement<QQuickRectangle>::~QQmlElement<QQuickRectangle> qqmlprivate.h 98 0x7ffbba9163cd 29 QQmlPrivate::QQmlElement<QQuickRectangle>::`scalar deleting destructor' Qt5Quickd 0x7ffbba9182f7 30 QQuickWidget::~QQuickWidget qquickwidget.cpp 403 0x7ffbd5af2e26 31 QQuickWidget::`scalar deleting destructor' QQuickWidgetCrashWhileDragging 0x7ff7e3ac5c38 32 qDeleteInEventHandler qobject.cpp 4455 0x6f294f8a 33 QObject::event qobject.cpp 1231 0x6f28d908 34 QWidget::event qwidget.cpp 9105 0x6e45a51e 35 QQuickWidget::event qquickwidget.cpp 1170 0x7ffbd5af51d7 36 QApplicationPrivate::notify_helper qapplication.cpp 3716 0x6e3f1fb6 37 QApplication::notify qapplication.cpp 3681 0x6e3ef773 38 QCoreApplication::notifyInternal qcoreapplication.cpp 965 0x6f23c9a4 39 QCoreApplication::sendEvent qcoreapplication.h 224 0x6f246ff3 40 QCoreApplicationPrivate::sendPostedEvents qcoreapplication.cpp 1593 0x6f23de4d 41 QEventDispatcherWin32::sendPostedEvents qeventdispatcher_win.cpp 1242 0x6f2ee46a 42 QWindowsGuiEventDispatcher::sendPostedEvents qwindowsguieventdispatcher.cpp 84 0x7ffbba4b91b4 43 qt_internal_proc qeventdispatcher_win.cpp 416 0x6f2ebe78 44 UserCallWinProcCheckWow USER32 0x7ffbeec0250d 45 DispatchMessageWorker USER32 0x7ffbeec02367 46 CDragOperation::HandleMessages drag.cpp 2230 0x7ffbed1dc9a4 47 DoDragDrop drag.cpp 2632 0x7ffbed1ddba7 48 QWindowsDrag::drag qwindowsdrag.cpp 811 0x7ffbba507fe6 49 QDragManager::drag qdnd.cpp 135 0x7ffbbb1e5080 50 QDrag::exec qdrag.cpp 274 0x7ffbbb1e2831 51 QDrag::exec qdrag.cpp 231 0x7ffbbb1e26de 52 MouseHandler::HandleMouseMove mousehandler.cpp 39 0x7ff7e3ac63bf 53 MouseHandler::qt_static_metacall moc_mousehandler.cpp 85 0x7ff7e3ac6cdb 54 MouseHandler::qt_metacall moc_mousehandler.cpp 119 0x7ff7e3ac6a97 55 QMetaObject::metacall qmetaobject.cpp 297 0x6f24a724 56 QQmlObjectOrGadget::metacall qqmlpropertycache.cpp 1690 0x69c3c3b7 57 CallMethod qv4qobjectwrapper.cpp 1157 0x69b4dbf0 58 CallPrecise qv4qobjectwrapper.cpp 1404 0x69b4e8dd 59 QV4::QObjectMethod::callInternal qv4qobjectwrapper.cpp 1893 0x69b4b1db 60 QV4::QObjectMethod::call qv4qobjectwrapper.cpp 1829 0x69b4aba7 61 QV4::Object::call qv4object_p.h 305 0x698259f5 62 QV4::Runtime::callProperty qv4runtime.cpp 977 0x69b70a75 63 0x824c1d0ebb 64 0x824a364180 65 0x8200000031 66 0x824c2f10b8 67 malloc dbgmalloc.c 56 0x7ffbbb011e9a
We have since prevented the ctrl+w action from executing while a drag in in progress.
You may recreate the issue in the following program, by clicking and dragging the red square. While still holding down the drag, hold ctrl+w and move the mouse. The program will assert after some mouse movement.
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