Qtwebengineprocess is not closed after application closing

Question

I have an application that uses Qt WebEngine. But I found that after closing my application or after crashing it "Qtwebengineprocess" still stays on. My app is too big to show it here, but here is a little example which also demostrates the problem:

#include <QApplication>
#include <QWebEngineView>
#include <QProcess>
#include <QTimer>


int main(int argc, char **argv)
{
    QApplication app(argc, argv);
    QWebEngineView* viewer = new QWebEngineView(NULL);
    viewer->show();
    viewer->load(QUrl("https://www.telegraph.co.uk/content/dam/Pets/spark/royal-canin/tabby-kitten-small.jpg?imwidth=1400"));
    QTimer::singleShot(2000, []() {
        exit(-1);
    });
    app.exec();
    delete viewer;

    return 0;
}

Did I forget to set up some thing? Or this is a Qt bug? Thanks in advance.

UPD: Qt 5.11, Win10

@eyllanesc, because it still remains. I can find it in the task manager — user2123079, Jul 27 '18 at 13:35
I just tried it in linux and the process disappears when the window closes. Does the process remain forever or does it die after a while? — eyllanesc, Jul 27 '18 at 13:37
@eyllanesc, process remain forever consuming CPU. I forgot to say, that I'm doing this on Windows — user2123079, Jul 27 '18 at 13:42
I recommend you to indicate the version of Qt, what is the version of your OS, etc, but it smells like a bug, report it. — eyllanesc, Jul 27 '18 at 13:49

Natsukane · Answer 1 · 2018-10-10T10:18:43.067

2

This seems to be a bug in PyQt 5.11 and above. After reinstalling my OS and installing the latest version of PyQt (5.11.3) I experienced this and other issues with QWebEngineView not resizing properly in layouts. Downgraded to PyQt 5.10.1 and everything ran properly again. If using Python, just run:

pip uninstall PyQt5
pip install PyQt5==5.10.1

edited Oct 10 '18 at 10:18

answered Oct 10 '18 at 04:00

Natsukane

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Thank's, but I use C++, not python. But I will test this bug on another versions of Qt – user2123079 Oct 10 '18 at 08:07
Yeah, my bad, didn't read the tags. But the same concept applies, downgrade to 5.10.1 and let us know how it goes. – Natsukane Oct 10 '18 at 10:14

score 2 · Accepted Answer · answered Oct 18 '18 at 15:21

2

I found actual issue and solution - here . This is Qt 5.11 bug that describes exactly this problem.

And one of the comments had solution that worked for me:

When running with QCoreApplication::setAttribute(Qt::AA_UseOpenGLES); 
at the top of the main() function, I'm observing that the qtwebengine process closes correctly, 
both when stopping the debugger and when the release exe crashes.

Just added that line before creation of my qApp and saw no crash whatsoever. Of course this comes with benefits and disadvantages of using ANGLE vs dynamic GPU on Qt, more details here.

answered Oct 18 '18 at 15:21

Shf

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It is strange, but I tried this solution for second time and it work now :/ Indeed, there are no WebEngine processes left anymore. This solution is fine for me, thank you! – user2123079 Jan 09 '19 at 14:47
1

note, that it should be fixed in Qt 5.12 as noted in bug url i linked in answer – Shf Jan 09 '19 at 15:44

score 0 · Answer 3 · answered Jul 28 '18 at 02:30

0

With reference to this post , when exit() is called in main(), no destructor will be called for locally scoped objects! exit() does not return.

Any code placed after app.exec(), (in your case delete viewer;), would be executed ONLY after main eventloop quits/exits and returns to caller, Your timer is calling (stdlib) exit() from within main loop, which means: you are exiting execution without return to caller, AND, none of your code placed AFTER app.exec() would be executed, if you want your code to run correctly and execute delete viewer;, then timer should quit main event loop thus you need to call app.quit() or app.exit(-1).

answered Jul 28 '18 at 02:30

Mohammad Kanan

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Yes, I know It. But the problem is that even without exit(-1) it sometimes have same behaviour as in the question. And also in linux this process is closed in any way. – user2123079 Jul 28 '18 at 06:47
@user2123079, this is almost waste of time. I run the corrected snippet on (win10/64 and Qt5.11/msvc2017 kit) and no bug is observed. – Mohammad Kanan Jul 28 '18 at 10:03
strange.. have the same environment.. I will make more experiments – user2123079 Jul 28 '18 at 13:07
process named "Qtwebengineprocess" which consumes CPU – user2123079 Jul 28 '18 at 13:20
@user2123079 How do run the application? – Mohammad Kanan Jul 28 '18 at 13:20
Double click on it or from Visual Studio - there is no difference – user2123079 Jul 28 '18 at 13:22
@user2123079, are you aware that `QWebEngine` should run only in `release` mode? – Mohammad Kanan Jul 28 '18 at 13:29
Problem remains for both debug and release builds – user2123079 Jul 29 '18 at 08:51
I observe same problem in qt 5.11 / vs 17 only if you terminate app sooner then page correctly loads. Try to load instead of jpg some heavy page that takes time to load and quit app. Webengine process will not be terminated. This is even worse if you have several QWQebengineviews running at the same time in app and user terminate app prematurely. – Shf Sep 06 '18 at 12:26
In qt 5.7 such issue was not present – Shf Sep 06 '18 at 12:45
@Shf, I will experiment with Qt versions and this bug. As soon as it will be done, I'll reply here about results – user2123079 Oct 10 '18 at 08:06

Qtwebengineprocess is not closed after application closing

3 Answers3