Qt6 Was: nearly 100% graphics pipe of Rx570 usage ...

[Duncan]

René J.V. Bertin posted on Mon, 04 Jul 2022 13:26:04 +0200 as excerpted:

> On Monday July 04 2022 10:09:50 Duncan wrote:

> I was surprised to see the other day that Qt is already at 6.2 or so.
> Definitely worth checking that version out, too!

Kinda OT for the thread so retitling for a new subthread.  Anyway, qt6...

Summary: the latest is actually 6.3, tho 6.2 is upstream LTS with a 3-year 
standard support term (for commercial users anyway, see below for further 
discussion), while 6.3 is only a standard 1-year-std-support release.

>From what I've read 6.0 was not really a practical "full" release, with 
many qt modules not yet ready and apparently, no API stability 
guarantees.  So in many ways it was a 6.x-developer-preview, hardly 
anything devs even wanted to port to yet.

Meanwhile, 5.15 LTS went commercial-only, from qt, leaving community/FLOSS 
users high and dry without a supported stable qt either old or new.  
That's why kde ultimately forked 5.15 and now they supply the 5.15 series 
community updates -- they really weren't left with much of a choice by qt 
upstream!  (Actually, kinda reminds me of the kde3->kde4 upgrade fiasco, 
the lessons of which kde at least seems to have taken to heart, which 
probably has a lot to do with them taking over 5.15 community maintenance 
rather than allowing themselves to be prematurely forced to the still very 
unstable early 6.0.)

But the 5.15 LTS (commercial release) got an extra two years of standard 
support for a total of five, which puts it ending in May of 2025, which 
means kde community 5.15 support will likely be ending around then as 
well.

Which in turn means kde really needs to have their 6.x-based stuff out 
there in 2023, giving people two years to get on qt6-based-kde before qt 
5.15 support goes dry in 2Q2025.

Meanwhile, back to 6.1, which ended up being in practice what arguably 
should have been was the .0 release.  Wikipedia says it was released May 
of 2021, with standard support lasting a year, to May of 2022, so it's 
already out of standard support.  But with only a year of standard support 
and being the first most devs even really started porting, it probably got 
only a very few user-level users, the reason it wasn't much on the radar, 
at least for users, either.

6.2 was the first 6.x LTS.  Released at the end of Sept 2021, being an LTS 
it has three years of standard support (commercially, anyway), so until 
the end of Sept 2024.

And if I'm not mistaken, this is where kde must have started getting 
serious with its porting.

Current is actually 6.3, now.  It's not LTS so only a year of standard 
support, but the focus is quality and bugfixes (many of which could make 
it into 6.2 LTS as well), and kde porting is coming along, so despite the 
non-LTS status it may be the first qt6 very early qt6-kde users see.  6.3 
was released in April 2022 so it'll be standard upstream qt supported 
until April 2023.

I don't actually know what the kde-targeted qt6 minimum is.  It may be 
they'll target 6.2 for its LTS, but I'm guessing they'll not actually 
consider anything qt6-kde-based stable for users until 6.4 (which 
following the 6-month-release-cadence should be later this year), thus 
allowing the possibility of requiring it for its presumable newer 
features, as well as allowing cutting out having to carry earlier 6.x 
compatibility backports by the time of actual release.

I think it's pretty safe to say, however, that particularly enterprise and 
long-term-support distros may not want to carry anything qt6-kde-based 
unless a qt-LTS is supported, and the next LTS is scheduled to be 6.5, so 
if kde folks don't target 6.2 LTS for support the enterprise-linux users 
are unlikely to get a qt6 kde until it can base on qt 6.5 LTS, which would 
be 2Q2023 and thus supported until 2Q2026.

And it's likely that in practice people (beyond "crazy" people like me 
that very well might be doing git-master kde on qt6 before the end of the 
year) won't be switching to qt6-based-kde until 1H2023 anyway, in which 
case going with the new 2Q2023 qt 6.5 LTS (which will presumably have a 
kde community supported LTS again as well) might be the best choice in any 
case.

As for kde qt6 status, from what I've seen running git-master and 
following the git logs (some more closely than others), I believe most 
(all?) of frameworks is ported and has running CI (constant integration) 
tests now.  Plasma and apps/gear are in process, tho I doubt any devs 
would consider even their "working-on-qt6" apps anything close to stable 
yet, and I think many that are "ported" to the extent that they build and 
may even run the CI, likely aren't practically /usable/ yet, as in some 
(many?) cases they've simply had the still-broken-on-qt6-bits IFDEFed out 
in ordered to just get something that builds and can pass enough tests to 
be worth running them to be sure what they've already done doesn't get 
broken by continuing changes.

IOW it's /well/ behind kde wayland support.  For those not yet running on 
wayland, then, qt6-kde is likely to be sometime next year (likely late 
next year) at the very earliest, while those running plasma on wayland 
might at least consider that it's an upcoming change, perhaps maybe worth 
testing later this year, tho early next is I think a bit more realistic.  
(Except that I'm speculating that with qt6 being the first qt developed 
/after/ wayland instead of with wayland support added /after-the-fact/, 
qt6 wayland support may be enough better than that of qt5, that for those 
on wayland, qt6 may be runnable, at least in a trade some qt5-wayland bugs 
for different qt6-general-bugs kind of way, somewhat earlier.)

In any event I'm sure it'll depend on the specific app, much as it did in 
the early qt4->qt5 upgrade era, when some apps were ready on qt5 months 
before others, which were only stable on qt4 for sometime longer.

But back to the original topic... There's probably not a lot of 
/independent/ qt6 software out there yet, but for the testing purposes of 
this thread the suggestion was upstream-distributed utilities in any case, 
and a 6.2/6.3 version of them should be available and usable.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman