[Development] A new approach for Qt main()

Lars Knoll lars.knoll at qt.io
Fri Dec 9 11:44:24 CET 2016

Well, the problem is that the main() entry point is causing huge amounts of issues on at least Android and iOS. We’d help those platforms a lot if we didn’t support this kind of entry point (on those platforms) anymore. But I agree that we can’t break this in Qt 5, but we can prepare for Qt6.

I’d propose to define a new entry point that works better on these platforms and offering that as the recommended way for new apps. The best solution is probably a static library that provides callbacks that can be used to initialize things.

When we then come to Qt6, we could deprecate using main() as the entry point, and remove support for it at least on the platforms where this is problematic.


From: Development <development-bounces+lars.knoll=qt.io at qt-project.org> on behalf of Simon Hausmann <Simon.Hausmann at qt.io>
Date: Friday, 9 December 2016 at 11:17
To: Friedemann Kleint <Friedemann.Kleint at qt.io>, Qt development mailing list <development at qt-project.org>
Subject: Re: [Development] A new approach for Qt main()

Yes, and we will forever (?) support that kind of main function and application entry point. I don't think that we can break that.

I'm all interested in supporting a second supported way of describing an entry point that more closely matches today's semantics

of graphics applications on the underlying operating/windowing systems.

Oddly, I do like the way that we're doing this on Windows and have been doing it forever, by shoehorning main() into WinMain()

through a static library. I'm not suggesting to replace QtMain, but I wonder if we could offer a cross-platform QtMain (with a different

name that doesn't clash with the existing one) that requires the programmer to supply a _two_ (or more?) functions instead of one function. No

macros involved then.


From: Development <development-bounces+simon.hausmann=qt.io at qt-project.org> on behalf of Friedemann Kleint <Friedemann.Kleint at qt.io>
Sent: Friday, December 9, 2016 11:00:00 AM
To: development at qt-project.org
Subject: Re: [Development] A new approach for Qt main()


 > Q_GUI_MAIN(appInit, appExit);

Magic macros for main should be avoided, IMO.

A typical application main() can look like

     QApplication a();

     Initialization code for other libraries

     parseArguments(), return if failed

     show some FileDialog prompting for argument if sth was missing

     try {
     } catch (exception) {
     De-Initialize something

There is no way to shoehorn this into some macro; this can already be
observed when trying to adding some initialization to a test.



Friedemann Kleint
The Qt Company GmbH

Development mailing list
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