Qt6 ports of applications

[Marius Kittler]

Hi,

let me share my experience as a KDE user and Qt programmer.

I've already started porting my non-KDE Qt apps (e.g. Syncthing Tray and Tag 
Editor) to Qt 6 while it hasn't even been released yet. In fact I'm actually 
already done with that apart from optional features which depend on KDE 
libraries or Qt WebEngine. It was not hard to make them compatible with both 
Qt versions at the same time but I was also not using much deprecated features 
anymore anyways (while actually still partially supporting Qt 5.6). To ease 
testing I also took care that the version linked against Qt 6 can be installed 
alongside the version linked against Qt 5. That includes of course underlying 
libraries.

When using the apps linked against Qt 6 under KDE it is of course apparent 
that KDE's platform integration and styling is missing. I've looked at the 
relevant source code but Qt's and KDE's major versions were hardcoded all over 
the place making it hard to port it to Qt 6 while retaining support for Qt 5. 
I've noticed the same when looking into Kirigami's build scripts. Due to this 
I didn't attempt to port any of these libraries at this point.

But wouldn't it make sense to support both versions at the same time and avoid 
the hardcoding? And maybe this counts for other "framework" libraries as well? 
Even if KDE has ported everything to Qt 6 we'd likely want the platform 
integration and styling for other applications which have not been ported to 
Qt 6 yet. And likely KDE itself will not be able to port everything at once 
(as many applications it is comprised of).

Best Regards
Marius