Showing QDialog in eventFilter()

**JPNaude** · 29th November 2010, 09:28

Hi

I'm wondering if it is a good idea to show a QDialog() in an event filter. I've recently been seeing crashes as soon as I call exec() on a dialog. I show the dialog by simply calling exec() on it. The code below is called as the result of a drop operation on a QTreeView which I catch in the event filter:

Qt Code:

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if (d->name_dialog->exec()) { // Crashes here (line 58 in the stack trace below)
    if (d->name_dialog->selectedResolution() == Reject)
        return_value = false;
    else
        return_value = true;

if (d->name_dialog->exec()) { // Crashes here (line 58 in the stack trace below)
    if (d->name_dialog->selectedResolution() == Reject)
        return_value = false;
    else
        return_value = true;

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Is this a basic mistake? If so what is the correct way to show a dialog in a event filter?

Thanks,
Jaco

Qt Code:

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0	qt_blend_argb32_on_argb32_sse2	emmintrin.h	1239	0x5931e8	
1	QRasterPaintEnginePrivate::drawImage	qpaintengine_raster.cpp	1067	0x73117f	
2	QRasterPaintEngine::drawImage	qpaintengine_raster.cpp	2761	0x739db9	
3	QRasterPaintEngine::drawPixmap	qpaintengine_raster.cpp	2419	0x737a8c	
4	QPainter::drawPixmap	qpainter.cpp	5387	0x6c9051	
5	QPainter::drawPixmap	qpainter.h	847	0xd09223	
6	QPixmapIconEngine::paint	qicon.cpp	146	0x62bb61	
7	QIcon::paint	qicon.cpp	722	0x62e1dc	
8	QCommonStyle::drawControl	qcommonstyle.cpp	2194	0x8406b3	
9	QWindowsStyle::drawControl	qwindowsstyle.cpp	2560	0x90c907	
10	QStyleSheetStyle::drawControl	qstylesheetstyle.cpp	3979	0x8766a6	
11	QStyledItemDelegate::paint	qstyleditemdelegate.cpp	424	0xb1326f	
12	QListView::paintEvent	qlistview.cpp	1044	0xa9ef69	
13	QWidget::event	qwidget.cpp	8333	0x5f492d	
14	QFrame::event	qframe.cpp	557	0x96e6bc	
15	QAbstractScrollArea::viewportEvent	qabstractscrollarea.cpp	1043	0x9fbf0f	
16	QAbstractItemView::viewportEvent	qabstractitemview.cpp	1619	0xa85785	
17	QAbstractScrollAreaPrivate::viewportEvent	qabstractscrollarea_p.h	100	0xc56a13	
18	QAbstractScrollAreaFilter::eventFilter	qabstractscrollarea_p.h	116	0xc5506c	
19	QCoreApplicationPrivate::sendThroughObjectEventFilters	qcoreapplication.cpp	847	0x6a1ffc73	
20	QApplicationPrivate::notify_helper	qapplication.cpp	4392	0x5a96e5	
21	QApplication::notify	qapplication.cpp	4361	0x5a9586	
22	QCoreApplication::notifyInternal	qcoreapplication.cpp	732	0x6a1ff9dc	
23	QCoreApplication::sendSpontaneousEvent	qcoreapplication.h	218	0xc1d53e	
24	QWidgetPrivate::drawWidget	qwidget.cpp	5420	0x5ed460	
25	QWidgetPrivate::paintSiblingsRecursive	qwidget.cpp	5627	0x5ee176	
26	QWidgetPrivate::drawWidget	qwidget.cpp	5473	0x5ed8ab	
27	QWidgetPrivate::paintSiblingsRecursive	qwidget.cpp	5627	0x5ee176	
28	QWidgetPrivate::paintSiblingsRecursive	qwidget.cpp	5614	0x5ee036	
29	QWidgetPrivate::drawWidget	qwidget.cpp	5473	0x5ed8ab	
30	QWidgetPrivate::paintSiblingsRecursive	qwidget.cpp	5627	0x5ee176	
31	QWidgetPrivate::paintSiblingsRecursive	qwidget.cpp	5614	0x5ee036	
32	QWidgetPrivate::drawWidget	qwidget.cpp	5473	0x5ed8ab	
33	QWidgetBackingStore::sync	qbackingstore.cpp	1320	0x774a5d	
34	QWidgetPrivate::syncBackingStore	qwidget.cpp	1805	0x5e4f50	
35	QWidget::event	qwidget.cpp	8480	0x5f4e75	
36	QMainWindow::event	qmainwindow.cpp	1417	0x98d23a	
37	QApplicationPrivate::notify_helper	qapplication.cpp	4396	0x5a9706	
38	QApplication::notify	qapplication.cpp	4361	0x5a9586	
39	QCoreApplication::notifyInternal	qcoreapplication.cpp	732	0x6a1ff9dc	
40	QCoreApplication::sendEvent	qcoreapplication.h	215	0xc1d592	
41	sendUpdateRequest	qbackingstore.cpp	507	0x771578	
42	QWidgetBackingStore::markDirty	qbackingstore.cpp	683	0x7721ba	
43	QWidget::repaint	qwidget.cpp	10237	0x5f778d	
44	QWidget::repaint	qwidget.cpp	10193	0x5f75b3	
45	setDisabledStyle	qwidget.cpp	8106	0xbd8a3e	
46	QWidget::event	qwidget.cpp	8502	0x5f4f6d	
47	QMainWindow::event	qmainwindow.cpp	1417	0x98d23a	
48	QApplicationPrivate::notify_helper	qapplication.cpp	4396	0x5a9706	
49	QApplication::notify	qapplication.cpp	4361	0x5a9586	
50	QCoreApplication::notifyInternal	qcoreapplication.cpp	732	0x6a1ff9dc	
51	QCoreApplication::sendEvent	qcoreapplication.h	215	0xc1d592	
52	QApplicationPrivate::enterModal	qapplication.cpp	2906	0x5a5a45	
53	QWidgetPrivate::show_helper	qwidget.cpp	7372	0x5f271b	
54	QWidget::setVisible	qwidget.cpp	7589	0x5f2f2d	
55	QDialog::setVisible	qdialog.cpp	739	0xa37528	
56	QWidget::show	qwidget.h	487	0xd08378	
57	QDialog::exec	qdialog.cpp	543	0xa36bbf	
58	Qtilities::CoreGui::NamingPolicyFilter::validateNamePropertyChange	NamingPolicyFilter.cpp	679	0x9374d93	
59	Qtilities::CoreGui::NamingPolicyFilter::initializeAttachment	NamingPolicyFilter.cpp	282	0x93703e3	
60	Qtilities::Core::Observer::attachSubject	Observer.cpp	866	0x6d0d7df5	
61	FirmwareCore::Design::addDesignFile	Design.cpp	493	0x6fcd69e8	
62	FirmwareCore::DesignManager::addFileToDesign	DesignManager.cpp	711	0x6fcd0481	
63	FirmwareCore::DesignWidget::eventFilter	DesignWidget.cpp	352	0x6fce8980	
64	QCoreApplicationPrivate::sendThroughObjectEventFilters	qcoreapplication.cpp	847	0x6a1ffc73	
65	QApplicationPrivate::notify_helper	qapplication.cpp	4392	0x5a96e5	
66	QApplication::notify	qapplication.cpp	4202	0x5a89ed	
67	QCoreApplication::notifyInternal	qcoreapplication.cpp	732	0x6a1ff9dc	
68	QCoreApplication::sendEvent	qcoreapplication.h	215	0xc1d592	
69	QOleDropTarget::Drop	qdnd_win.cpp	819	0x617326	
70	ole32!StgGetIFillLockBytesOnFile	C:\WINDOWS\system32\ole32.dll	0	0x775f8ec6	
71	ole32!StgGetIFillLockBytesOnFile	C:\WINDOWS\system32\ole32.dll	0	0x775f9108	
72	ole32!CreateErrorInfo	C:\WINDOWS\system32\ole32.dll	0	0x775cfce8	
73	ole32!CreateErrorInfo	C:\WINDOWS\system32\ole32.dll	0	0x775cfb70	
74	QDragManager::drag	qdnd_win.cpp	942	0x617851	
75	QDrag::exec	qdrag.cpp	284	0x5b2b90	
76	QAbstractItemView::startDrag	qabstractitemview.cpp	3437	0xa8d56a	
77	QAbstractItemView::mouseMoveEvent	qabstractitemview.cpp	1700	0xa85f7f	
78	QTreeView::mouseMoveEvent	qtreeview.cpp	1902	0xabcc04	
79	QWidget::event	qwidget.cpp	8172	0x5f4164	
80	QFrame::event	qframe.cpp	557	0x96e6bc	
81	QAbstractScrollArea::viewportEvent	qabstractscrollarea.cpp	1043	0x9fbf0f	
82	QAbstractItemView::viewportEvent	qabstractitemview.cpp	1619	0xa85785	
83	QTreeView::viewportEvent	qtreeview.cpp	1256	0xab9aa3	
84	QAbstractScrollAreaPrivate::viewportEvent	qabstractscrollarea_p.h	100	0xc56a13	
85	QAbstractScrollAreaFilter::eventFilter	qabstractscrollarea_p.h	116	0xc5506c	
86	QCoreApplicationPrivate::sendThroughObjectEventFilters	qcoreapplication.cpp	847	0x6a1ffc73	
87	QApplicationPrivate::notify_helper	qapplication.cpp	4392	0x5a96e5	
88	QApplication::notify	qapplication.cpp	3959	0x5a7909	
89	QCoreApplication::notifyInternal	qcoreapplication.cpp	732	0x6a1ff9dc	
90	QCoreApplication::sendSpontaneousEvent	qcoreapplication.h	218	0xc1d53e	
91	QApplicationPrivate::sendMouseEvent	qapplication.cpp	3056	0x5a6118	
92	QETWidget::translateMouseEvent	qapplication_win.cpp	3317	0x60fc63	
93	QtWndProc@16	qapplication_win.cpp	1657	0x60aaa6	
94	USER32!GetDC	C:\WINDOWS\system32\user32.dll	0	0x7e418734	
95	??		0	0x26091e	
96	??		0	0x200	
97	USER32!GetDC	C:\WINDOWS\system32\user32.dll	0	0x7e418816	
98	qt_is_translatable_mouse_event	qapplication_win.cpp	1426	0x609fa5	
99	USER32!GetWindowLongW	C:\WINDOWS\system32\user32.dll	0	0x7e4189cd	
100	??		0

0	qt_blend_argb32_on_argb32_sse2	emmintrin.h	1239	0x5931e8	
1	QRasterPaintEnginePrivate::drawImage	qpaintengine_raster.cpp	1067	0x73117f	
2	QRasterPaintEngine::drawImage	qpaintengine_raster.cpp	2761	0x739db9	
3	QRasterPaintEngine::drawPixmap	qpaintengine_raster.cpp	2419	0x737a8c	
4	QPainter::drawPixmap	qpainter.cpp	5387	0x6c9051	
5	QPainter::drawPixmap	qpainter.h	847	0xd09223	
6	QPixmapIconEngine::paint	qicon.cpp	146	0x62bb61	
7	QIcon::paint	qicon.cpp	722	0x62e1dc	
8	QCommonStyle::drawControl	qcommonstyle.cpp	2194	0x8406b3	
9	QWindowsStyle::drawControl	qwindowsstyle.cpp	2560	0x90c907	
10	QStyleSheetStyle::drawControl	qstylesheetstyle.cpp	3979	0x8766a6	
11	QStyledItemDelegate::paint	qstyleditemdelegate.cpp	424	0xb1326f	
12	QListView::paintEvent	qlistview.cpp	1044	0xa9ef69	
13	QWidget::event	qwidget.cpp	8333	0x5f492d	
14	QFrame::event	qframe.cpp	557	0x96e6bc	
15	QAbstractScrollArea::viewportEvent	qabstractscrollarea.cpp	1043	0x9fbf0f	
16	QAbstractItemView::viewportEvent	qabstractitemview.cpp	1619	0xa85785	
17	QAbstractScrollAreaPrivate::viewportEvent	qabstractscrollarea_p.h	100	0xc56a13	
18	QAbstractScrollAreaFilter::eventFilter	qabstractscrollarea_p.h	116	0xc5506c	
19	QCoreApplicationPrivate::sendThroughObjectEventFilters	qcoreapplication.cpp	847	0x6a1ffc73	
20	QApplicationPrivate::notify_helper	qapplication.cpp	4392	0x5a96e5	
21	QApplication::notify	qapplication.cpp	4361	0x5a9586	
22	QCoreApplication::notifyInternal	qcoreapplication.cpp	732	0x6a1ff9dc	
23	QCoreApplication::sendSpontaneousEvent	qcoreapplication.h	218	0xc1d53e	
24	QWidgetPrivate::drawWidget	qwidget.cpp	5420	0x5ed460	
25	QWidgetPrivate::paintSiblingsRecursive	qwidget.cpp	5627	0x5ee176	
26	QWidgetPrivate::drawWidget	qwidget.cpp	5473	0x5ed8ab	
27	QWidgetPrivate::paintSiblingsRecursive	qwidget.cpp	5627	0x5ee176	
28	QWidgetPrivate::paintSiblingsRecursive	qwidget.cpp	5614	0x5ee036	
29	QWidgetPrivate::drawWidget	qwidget.cpp	5473	0x5ed8ab	
30	QWidgetPrivate::paintSiblingsRecursive	qwidget.cpp	5627	0x5ee176	
31	QWidgetPrivate::paintSiblingsRecursive	qwidget.cpp	5614	0x5ee036	
32	QWidgetPrivate::drawWidget	qwidget.cpp	5473	0x5ed8ab	
33	QWidgetBackingStore::sync	qbackingstore.cpp	1320	0x774a5d	
34	QWidgetPrivate::syncBackingStore	qwidget.cpp	1805	0x5e4f50	
35	QWidget::event	qwidget.cpp	8480	0x5f4e75	
36	QMainWindow::event	qmainwindow.cpp	1417	0x98d23a	
37	QApplicationPrivate::notify_helper	qapplication.cpp	4396	0x5a9706	
38	QApplication::notify	qapplication.cpp	4361	0x5a9586	
39	QCoreApplication::notifyInternal	qcoreapplication.cpp	732	0x6a1ff9dc	
40	QCoreApplication::sendEvent	qcoreapplication.h	215	0xc1d592	
41	sendUpdateRequest	qbackingstore.cpp	507	0x771578	
42	QWidgetBackingStore::markDirty	qbackingstore.cpp	683	0x7721ba	
43	QWidget::repaint	qwidget.cpp	10237	0x5f778d	
44	QWidget::repaint	qwidget.cpp	10193	0x5f75b3	
45	setDisabledStyle	qwidget.cpp	8106	0xbd8a3e	
46	QWidget::event	qwidget.cpp	8502	0x5f4f6d	
47	QMainWindow::event	qmainwindow.cpp	1417	0x98d23a	
48	QApplicationPrivate::notify_helper	qapplication.cpp	4396	0x5a9706	
49	QApplication::notify	qapplication.cpp	4361	0x5a9586	
50	QCoreApplication::notifyInternal	qcoreapplication.cpp	732	0x6a1ff9dc	
51	QCoreApplication::sendEvent	qcoreapplication.h	215	0xc1d592	
52	QApplicationPrivate::enterModal	qapplication.cpp	2906	0x5a5a45	
53	QWidgetPrivate::show_helper	qwidget.cpp	7372	0x5f271b	
54	QWidget::setVisible	qwidget.cpp	7589	0x5f2f2d	
55	QDialog::setVisible	qdialog.cpp	739	0xa37528	
56	QWidget::show	qwidget.h	487	0xd08378	
57	QDialog::exec	qdialog.cpp	543	0xa36bbf	
58	Qtilities::CoreGui::NamingPolicyFilter::validateNamePropertyChange	NamingPolicyFilter.cpp	679	0x9374d93	
59	Qtilities::CoreGui::NamingPolicyFilter::initializeAttachment	NamingPolicyFilter.cpp	282	0x93703e3	
60	Qtilities::Core::Observer::attachSubject	Observer.cpp	866	0x6d0d7df5	
61	FirmwareCore::Design::addDesignFile	Design.cpp	493	0x6fcd69e8	
62	FirmwareCore::DesignManager::addFileToDesign	DesignManager.cpp	711	0x6fcd0481	
63	FirmwareCore::DesignWidget::eventFilter	DesignWidget.cpp	352	0x6fce8980	
64	QCoreApplicationPrivate::sendThroughObjectEventFilters	qcoreapplication.cpp	847	0x6a1ffc73	
65	QApplicationPrivate::notify_helper	qapplication.cpp	4392	0x5a96e5	
66	QApplication::notify	qapplication.cpp	4202	0x5a89ed	
67	QCoreApplication::notifyInternal	qcoreapplication.cpp	732	0x6a1ff9dc	
68	QCoreApplication::sendEvent	qcoreapplication.h	215	0xc1d592	
69	QOleDropTarget::Drop	qdnd_win.cpp	819	0x617326	
70	ole32!StgGetIFillLockBytesOnFile	C:\WINDOWS\system32\ole32.dll	0	0x775f8ec6	
71	ole32!StgGetIFillLockBytesOnFile	C:\WINDOWS\system32\ole32.dll	0	0x775f9108	
72	ole32!CreateErrorInfo	C:\WINDOWS\system32\ole32.dll	0	0x775cfce8	
73	ole32!CreateErrorInfo	C:\WINDOWS\system32\ole32.dll	0	0x775cfb70	
74	QDragManager::drag	qdnd_win.cpp	942	0x617851	
75	QDrag::exec	qdrag.cpp	284	0x5b2b90	
76	QAbstractItemView::startDrag	qabstractitemview.cpp	3437	0xa8d56a	
77	QAbstractItemView::mouseMoveEvent	qabstractitemview.cpp	1700	0xa85f7f	
78	QTreeView::mouseMoveEvent	qtreeview.cpp	1902	0xabcc04	
79	QWidget::event	qwidget.cpp	8172	0x5f4164	
80	QFrame::event	qframe.cpp	557	0x96e6bc	
81	QAbstractScrollArea::viewportEvent	qabstractscrollarea.cpp	1043	0x9fbf0f	
82	QAbstractItemView::viewportEvent	qabstractitemview.cpp	1619	0xa85785	
83	QTreeView::viewportEvent	qtreeview.cpp	1256	0xab9aa3	
84	QAbstractScrollAreaPrivate::viewportEvent	qabstractscrollarea_p.h	100	0xc56a13	
85	QAbstractScrollAreaFilter::eventFilter	qabstractscrollarea_p.h	116	0xc5506c	
86	QCoreApplicationPrivate::sendThroughObjectEventFilters	qcoreapplication.cpp	847	0x6a1ffc73	
87	QApplicationPrivate::notify_helper	qapplication.cpp	4392	0x5a96e5	
88	QApplication::notify	qapplication.cpp	3959	0x5a7909	
89	QCoreApplication::notifyInternal	qcoreapplication.cpp	732	0x6a1ff9dc	
90	QCoreApplication::sendSpontaneousEvent	qcoreapplication.h	218	0xc1d53e	
91	QApplicationPrivate::sendMouseEvent	qapplication.cpp	3056	0x5a6118	
92	QETWidget::translateMouseEvent	qapplication_win.cpp	3317	0x60fc63	
93	QtWndProc@16	qapplication_win.cpp	1657	0x60aaa6	
94	USER32!GetDC	C:\WINDOWS\system32\user32.dll	0	0x7e418734	
95	??		0	0x26091e	
96	??		0	0x200	
97	USER32!GetDC	C:\WINDOWS\system32\user32.dll	0	0x7e418816	
98	qt_is_translatable_mouse_event	qapplication_win.cpp	1426	0x609fa5	
99	USER32!GetWindowLongW	C:\WINDOWS\system32\user32.dll	0	0x7e4189cd	
100	??		0

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**wysota** · 29th November 2010, 09:45

Yes, I think that's something you shouldn't do. I don't know what you are doing but probably you can do it outside an event filter.

**franz** · 29th November 2010, 19:23

If you really think you have to, you should call open() on the dialog, not exec(). exec() starts another event loop leading to all kinds of unpredictable behavior.