QPrintPreviewDialog crashes on selecting print button.
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@Kenchan Will post the debugging result once I am able to reproduce. It is Sporadic. It happens only once in a while. In last 10 days it happened only 2-3 times. That is the problem.
call stack when last time it crashed. This may not help as it is not full call stack. But still.
Thu Nov 30 18:59:44 2017 Logger.cpp logStackTrace : 670 Stack Trace: Segmentation Fault
/usr/local/qt/lib/libQt5PrintSupport.so.5(+0x38a62) [0x7fa8d35b1a62]
/usr/local/qt/lib/libQt5PrintSupport.so.5(+0x4f563) [0x7fa8d35c8563]
/usr/local/qt/lib/libQt5Core.so.5(_ZN11QMetaObject8activateEP7QObjectiiPPv+0x2c1) [0x7fa8d23bf521]
/usr/local/qt/lib/libQt5Widgets.so.5(_ZN9QLineEdit13focusOutEventEP11QFocusEvent+0x89) [0x7fa8d31b8189]
/usr/local/qt/lib/libQt5Widgets.so.5(_ZN7QWidget5eventEP6QEvent+0x57c) [0x7fa8d30c7cfc]
/usr/local/qt/lib/libQt5Widgets.so.5(_ZN9QLineEdit5eventEP6QEvent+0x65) [0x7fa8d31b7ba5]
/usr/local/qt/lib/libQt5Widgets.so.5(_ZN7QWidget5eventEP6QEvent+0x57c) [0x7fa8d30c7cfc]
/usr/local/qt/lib/libQt5Widgets.so.5(_ZN9QComboBox5eventEP6QEvent+0x76) [0x7fa8d31783b6]
/usr/local/qt/lib/libQt5Widgets.so.5(_ZN19QApplicationPrivate13notify_helperEP7QObjectP6QEvent+0x9c) [0x7fa8d308632c]
/usr/local/qt/lib/libQt5Widgets.so.5(_ZN12QApplication6notifyEP7QObjectP6QEvent+0x3fa) [0x7fa8d308a98a] -
@Sheetal OK, i can't see anything in the code that will directly cause a crash. I would be concerned about keeping the m_printer in sync with what the preview dialog settings. Since you are not using the pointer that gets passed into the print function from the print preview dialog your member function will not get updated with those setting. As you are forcing it to print to a pdf file maybe this is not so important.
I have been using the QPrintPreviewWidget in my own dialog since before 5.6.0 an have not seen intermittent crashes. I only ever had problems with the printer object not being valid in some way but I make sure that does not happen any more.
I only use the printer pointer passed into the print function and sync my current printer and it's settings from the one currently managed by the widget, which may or may not be the one I passed to it in the first place.
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@Kenchan Will post the debugging result once I am able to reproduce. It is Sporadic. It happens only once in a while. In last 10 days it happened only 2-3 times. That is the problem.
call stack when last time it crashed. This may not help as it is not full call stack. But still.
Thu Nov 30 18:59:44 2017 Logger.cpp logStackTrace : 670 Stack Trace: Segmentation Fault
/usr/local/qt/lib/libQt5PrintSupport.so.5(+0x38a62) [0x7fa8d35b1a62]
/usr/local/qt/lib/libQt5PrintSupport.so.5(+0x4f563) [0x7fa8d35c8563]
/usr/local/qt/lib/libQt5Core.so.5(_ZN11QMetaObject8activateEP7QObjectiiPPv+0x2c1) [0x7fa8d23bf521]
/usr/local/qt/lib/libQt5Widgets.so.5(_ZN9QLineEdit13focusOutEventEP11QFocusEvent+0x89) [0x7fa8d31b8189]
/usr/local/qt/lib/libQt5Widgets.so.5(_ZN7QWidget5eventEP6QEvent+0x57c) [0x7fa8d30c7cfc]
/usr/local/qt/lib/libQt5Widgets.so.5(_ZN9QLineEdit5eventEP6QEvent+0x65) [0x7fa8d31b7ba5]
/usr/local/qt/lib/libQt5Widgets.so.5(_ZN7QWidget5eventEP6QEvent+0x57c) [0x7fa8d30c7cfc]
/usr/local/qt/lib/libQt5Widgets.so.5(_ZN9QComboBox5eventEP6QEvent+0x76) [0x7fa8d31783b6]
/usr/local/qt/lib/libQt5Widgets.so.5(_ZN19QApplicationPrivate13notify_helperEP7QObjectP6QEvent+0x9c) [0x7fa8d308632c]
/usr/local/qt/lib/libQt5Widgets.so.5(_ZN12QApplication6notifyEP7QObjectP6QEvent+0x3fa) [0x7fa8d308a98a] -
Thanks for the reply @kenchan . Will definitely try changing the m_printer to the one passed in the print() slot. (In this case "p")
Will post the results.@Sheetal Another thing that concerns me is keeping the painter as a class member. Looking at the code you could create it on each call in the print function and pass it as a pointer to the other functions that need it when they are called from the print function. The painter would go out of scope at the end of the print function. I am not used to using a painter in any other way, I believe there are restrictions on how and when a painter can be used.
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@Sheetal OK, i can't see anything in the code that will directly cause a crash. I would be concerned about keeping the m_printer in sync with what the preview dialog settings. Since you are not using the pointer that gets passed into the print function from the print preview dialog your member function will not get updated with those setting. As you are forcing it to print to a pdf file maybe this is not so important.
I have been using the QPrintPreviewWidget in my own dialog since before 5.6.0 an have not seen intermittent crashes. I only ever had problems with the printer object not being valid in some way but I make sure that does not happen any more.
I only use the printer pointer passed into the print function and sync my current printer and it's settings from the one currently managed by the widget, which may or may not be the one I passed to it in the first place.
@kenchan said in QPrintPreviewDialog crashes on selecting print button.:
I only use the printer pointer passed into the print function and sync my current printer and it's settings from the one currently managed by the widget, which may or may not be the one I passed to it in the first place.
I did not get "sync my current printer and it's settings from the one currently managed by the widget, which may or may not be the one I passed to it in the first place."
U mean , I should have a m_printer pointer as class member and pass it to QPrintPreviewDialog(), and then in print(QPainter p) slot I should assign p=m_printer?
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@kenchan said in QPrintPreviewDialog crashes on selecting print button.:
I only use the printer pointer passed into the print function and sync my current printer and it's settings from the one currently managed by the widget, which may or may not be the one I passed to it in the first place.
I did not get "sync my current printer and it's settings from the one currently managed by the widget, which may or may not be the one I passed to it in the first place."
U mean , I should have a m_printer pointer as class member and pass it to QPrintPreviewDialog(), and then in print(QPainter p) slot I should assign p=m_printer?
@Sheetal Well, As it tells you in the docs for the QPrintPreviewDialog, you can let the dialog provide a printer or you provide it with one.
You can have a printer member as a pointer or as you have it now, but you must know that the user can change the printer and or it settings using the dialog. This means the type of printer and or its settings may change between when the dialog is created and when the print function is called. You must allow for that by and make sure the printer is what you expect when you do the drawing on it.When I use my dialog I do the following:
I get a pointer to the default printer make any settings I want to set then pass it to the dialog in its constructor.
I make the connection to the print function.
I call exec on the dialog.
The print function is called.
I use the printer pointer passed in and create a painter with it.
I draw on the painter.
The dialog shows the user the preview.
The user may change the paper size or even the printer etc. The print function can be called again when a change is made.
The user clicks the print button.
The pages get printed to the printer or pdf file whichever the case maybe.
The dialog closes.
I delete the printer.I hope this helps.
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I am able to get the complete call stack when it crashed. It is as below.
There is no problem with painter & printer objects (I have corrected my code as per our previous discussion ). When I debug all calls are made correctly. Nothing suspicious .
But, looks like when QPrintPreviewDialog is getting destroyed by Qt at the end of printing there is a problem. or Maybe some events are getting generated after preview dialog is closed.
1 CLogger::handleSignal Logger.cpp 618 0x7fe3529e1f27
2 __restore_rt 0x7fe34d06e250
3 ?? 0x180a090
4 QPrintPreviewWidgetPrivate::setZoomFactor(double) 0x7fe34f87fa65
5 QPrintPreviewDialogPrivate::_q_zoomFactorChanged() 0x7fe34f896563
6 QMetaObject::activate(QObject *, int, int, void * *) 0x7fe34e68d521
7 QLineEdit::focusOutEvent(QFocusEvent *) 0x7fe34f486189
8 QWidget::event(QEvent *) 0x7fe34f395cfc
9 QLineEdit::event(QEvent *) 0x7fe34f485ba5
10 QWidget::event(QEvent *) 0x7fe34f395cfc
11 QComboBox::event(QEvent *) 0x7fe34f4463b6
12 QApplicationPrivate::notify_helper(QObject *, QEvent *) 0x7fe34f35432c
13 QApplication::notify(QObject *, QEvent *) 0x7fe34f35898a
14 OdvApplication::notify OdvApplication.cpp 53 0x63d13d
15 QCoreApplication::notifyInternal2(QObject *, QEvent *) 0x7fe34e663a75
16 QApplicationPrivate::setFocusWidget(QWidget *, Qt::FocusReason) 0x7fe34f3565c3
17 QApplication::setActiveWindow(QWidget *) 0x7fe34f356c14
18 QApplicationPrivate::notifyActiveWindowChange(QWindow *) 0x7fe34f356cc3
19 QGuiApplicationPrivate::processActivatedEvent(QWindowSystemInterfacePrivate::ActivatedWindowEvent *) 0x7fe34e9b4635
20 QGuiApplicationPrivate::processWindowSystemEvent(QWindowSystemInterfacePrivate::WindowSystemEvent *) 0x7fe34e9b498d
21 QWindowSystemInterface::sendWindowSystemEvents(QFlagsQEventLoop::ProcessEventsFlag) 0x7fe34e99696b
22 userEventSourceDispatch(_GSource *, int ( *)(void *), void *) 0x7fe34e2d9cb0
23 g_main_context_dispatch 0x7fe3470b5d7a
24 g_main_context_iterate.isra.24 0x7fe3470b60b8
25 g_main_context_iteration 0x7fe3470b616c
26 QEventDispatcherGlib::processEvents(QFlagsQEventLoop::ProcessEventsFlag) 0x7fe34e6b3a9c
27 QEventLoop::exec(QFlagsQEventLoop::ProcessEventsFlag) 0x7fe34e661c1b
28 QCoreApplication::exec() 0x7fe34e669956
29 main SVGViewMain.cpp 283 0x66a54d