Who closes application on Escape?

[django.Reinhard]

Hi,

I accidently hit Escape and the application was closed as fast as possible.
I was astonished, as I did not code that feature.

And as I don't want that feature, I tried to find the source of it.
Adding keyPressEvent to MainWindow did not work.
So I started Application in debugger and put a breakpoint at QApplication::event() but debugger did not stop at Escape.

According Qt documentation of QKeySequence there's no standard shortcut bound to Escape-key beside QKeySequence::Cancel but I could not find the source, where Escape should close the application.

Debugger just says that application has finished with exit-code 0.

How can I find out, who is responsible for closing application?

[JonB]

@django-Reinhard
If you have an application consisting of just a QMainWindow I do not believe Escape will close/exit it. Maybe you have something else, I don't know.

[Pl45m4]

@django-Reinhard

Every QDialog subclass will receive a reject on ESC-key and close afterwards (or whatever you do when it got rejected).

Edit:

And even if you have a QMainWindow but it's hidden at this moment, the dialog will receive a reject and your QApp will exit properly.

• https://doc.qt.io/qt-5/qguiapplication.html#quitOnLastWindowClosed-prop

Damn @J-Hilk, I was editing my post, when you wrote the same I was about to write :)

[J.Hilk]

to add to @Pl45m4
if you have a QDialog open, and all other widgets are hidden, and you press esc, than due to
https://doc.qt.io/qt-5/qguiapplication.html#quitOnLastWindowClosed-prop property, that is by default set to true, your whole program should close

---

@Pl45m4 great minds think alike 😎

[JonB]

I'm sure the OP would have said if he had a QDialog open and was pressing the Escape key there.....

[Pl45m4]

@JonB said in Who closes application on Escape?:

I'm sure the OP would have said if he had a QDialog open and was pressing the Escape key there.....

There is no other possibility than this... A QMainWindow never closes on ESC by default unless you modify key- and closeEvents.

Edit:
It's more likely our 2nd guess... Maybe the QMainWindow was hidden and some dialog the last visible widget.

[JonB]

@Pl45m4
I agree, which is what I said. Just I'm sure the OP would have mentioned this vital piece of information if he were using a dialog, another window, or the main window was closed/hidden.... :)

[J.Hilk]

@JonB said in Who closes application on Escape?:

I'm sure the OP would have said if he had a QDialog open and was pressing the Escape key there.....

your faith in humanity is adorable 😘

[Pl45m4]

@JonB said in Who closes application on Escape?:

Just I'm sure the OP would have mentioned this vital piece of information if he were using a dialog

Haha. What I've learned from almost 3 years of being active here: Never trust OP's description of any issue :))

[django.Reinhard]

Thank you all for your attention!

... and no! I'm not using or talking about any dialog.

I'm talking about QMainWindow.
A dialog closing on escape wouldn't have surprised me at all.

Just to be detailed and clear:
I have only QMainWindow open. This window is enriched by lots of dockables and several widgets have keyPressed overridden.

When I close the application by menu action or by titlebar button, a messagebox pops up to ask, whether I wonna close the app.

When I hit escape, the application shuts down that fast as if I would throw an exception. That has surprised me.
If I debug the app and an exception is thrown, the debugger tells me, that it had received a kill signal and I see the stack, so I can investigate what happened.
In this case, the debugger says nothing and there's no stacktrace.

The app has just terminated as intended.

I added a debug message to main after application::exec and that message is printed. So Escape terminates the eventloop and the main function ends normally.

[JonB]

@django-Reinhard said in Who closes application on Escape?:

and several widgets have keyPressed overridden.

I can only think that somehow this is relevant. Remove all of this, or better still create a standalone 4-line program which just opens a QMainWindow and verify that Escape does not end the application. Then work back/forward from there, because the way you describe it sounds like the Qt app is indeed exiting "cleanly" if it returns from QApplication::exec().

[Pl45m4]

@django-Reinhard said in Who closes application on Escape?:

Debugger just says that application has finished with exit-code 0.

A crash would not result in exit code 0.
Probably there is something wrong with your keyHandler

[django.Reinhard]

Hi,

thanks to your numerous "Qt won't do that" it was easy to me to find the culprit.

@JonB said in Who closes application on Escape?:

I can only think that somehow this is relevant.

You're right.
I use an opencascade widget, which I didn't spend much time for investigation. I just used it as is. And that widget killed the app at Escape key press.

Anyway - with this lesson I learned a lot about event-handling in Qt.