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.