[libcamera-devel] [PATCH v2 1/3] apps: qcam: Port to Qt 6

[Neal Gompa]

On Mon, Jan 22, 2024 at 5:31 PM Kieran Bingham
<kieran.bingham at ideasonboard.com> wrote:
>
> Quoting Neal Gompa (2024-01-22 19:55:20)
> > On Mon, Jan 22, 2024 at 11:02 AM Kieran Bingham
> > <kieran.bingham at ideasonboard.com> wrote:
> > >
> > > > > > > > > So it's just Ubuntu/Canonical holding us back here ...
> > > > > > > > >
> > > > > > > > > Any thoughts anyone?
> > > > > > > >
> > > > > > > > I was hoping jammy-backports would help us, but that doesn't seem to be
> > > > > > > > the case :-(
> > > > > > > >
> > > > > > > > As there doesn't seem to be an urgency to switch to Qt 6 (unless I'm
> > > > > > > > missing something), I'm tempted to propose waiting until Ubuntu 24.04
> > > > > > > > gets released.
>
> Is there an urgency? Is there a requirement to move to QT6 for Fedora or
> otherwise?
>
> > > > > > >
> > > > > > > Noble (24.04) will have either 1.2.1 or 1.3.1 (there are different
> > > > > > > versions in proposed and Release). Either way it will be > 1.2! :
> > > > > > >   https://launchpad.net/ubuntu/noble/+package/meson
> > > > > > >
> > > > > > > I would propose that the meson version update is separated from the
> > > > > > > patch as a preceeding commit, and could already be resent. Then we can
> > > > > > > simply pick these in April. I'd probably say we could merge this in
> > > > > > > early April, such that we can make a release of libcamera with that
> > > > > > > support merged soon after Ubuntu 24.04 is released on April 25th.
> > > > > > >
> > > > > >
> > > > > > On the flip side, if it's merged and released into Debian before the
> > > > > > Ubuntu freeze on Feb 29[1], then it would be part of Ubuntu 24.04
> > > > > > itself.
> > > > >
> > > > > That's an interesting take too.
> > > > >
> > > > > Which one is the chicken and which one is the egg?
> > > > >
> > > > > Our early requirement for meeting the dependencies in the distributions
> > > > > was because the distributions themselves were not including libcamera.
> > > > > Therefore, users of libcamera /had/ to be able to build libcamera.
> > > > >
> > > > > Now that things can be included, perhaps that's reason enough to say
> > > > > aiming for integration is better.
> > > > >
> > > > > > [1]: https://discourse.ubuntu.com/t/noble-numbat-release-schedule/35649
> > > > >
> > > > > It looks like libcamera-0.2 is already included in the noble release, so
> > > > > package updates into debian look like they get into Ubuntu quite 'fast'.
> > > > >
> > > > > I feel like targetting getting /into/ the next Ubuntu LTS with updates
> > > > > is better than working on /top/ of it.
> > > > >
> > > > > The expense/cost is that in between we would no longer support compiling
> > > > > the master branch (or intermediate releases) with the 'current' LTS of
> > > > > Ubuntu.
> > > > >
> > > > > I could say "Oh well, that probably doesn't matter" ... except ... I use
> > > > > Ubuntu-22.04 as my main distro ... and I would plan to upgrade at the
> > > > > next release.
> > > > >
> > > > > I'm aware that I can work around this issue by upgrading meson myself.
> > > > > The question is what will happen to others ... and maybe it's just
> > > > > something we should bite and help them upgrade meson in the interim.
> > > > >
> > > >
> > > > Well, in a previous life I used to maintain Meson backports for Ubuntu.
> > > >
> > > > I'm happy to provide a package (based on the CentOS 9 one) for Ubuntu
> > > > 22.04 until 24.04 is released if it would help you:
> > > > https://software.opensuse.org//download.html?project=home%3APharaoh_Atem%3AMeson&package=meson
> > >
> > > Is there an official Ubuntu channel for that? If you can make
> > > 'ubuntu-22.04' support a later meson - I have no argument to prevent this
> > > being merged already!
> > >
> >
> > No. At this point, it would be unlikely to get updated unless you know
> > someone who can ship something in jammy-backports. But even then, with
> > 24.04 coming in a few months, 22.04 has been in its zombie period for
> > a while now. Typically, the expectation is that you either use later
> > Ubuntu STS releases (23.10 is a perfectly fine release, as an example)
> > or backport what you need while you wait for the next LTS.
> >
> > If you intend to hold back the patch until after 24.04 releases, then
> > there is no chance for this to be part of Ubuntu 24.04 itself, which I
> > think would be a shame. I prepared a backport for meson for Ubuntu
> > 22.04 because you said it would help you for developing on 22.04. I am
>
> I myself am quite capable of updating meson. I was highlighting that
> there are 'users' of Ubuntu 22.04. Our aim for libcamera has always been
> to make sure that libcamera can be built on the 'main distributions'.
> For which we define that as 'the latest LTS of the big distros'.
>
> My question above was because it sounded like you could get that solved
> by fixing the one remaining stuck-in-the-past distro which is blocking
> us.
>
> "> Well, in a previous life I used to maintain Meson backports for Ubuntu."
>
> And if you could do that - there would be nothing blocking the patch!
>

Unfortunately, not in Ubuntu proper. I did it outside of the distribution.

It's actually very hard to get a backport of Meson through because it
is not behavior-stable across releases. This is incredibly important
for Debian and Ubuntu, which is likely why Meson almost never sees
official backports. Even CentOS Meson upgrades required a lot of work
to bend new releases to be more backward compatible so nothing would
break.

> > not about to ask you to move to Fedora (which is what I use) or CentOS
> > Stream 9 (which would be an analogous LTS that does have a recent
> > enough Meson).
> >
> > My only argument at this point is that you can choose to include the
> > patch now and make a release so it can land in Debian sid now, and
> > thus make it into Ubuntu 24.04 so that Ubuntu users will benefit from
> > it. From my perspective, I want this so that Fedora users and later
> > CentOS 10 users will benefit from it. I also think that Debian/Ubuntu
>
> The question for us though is how many people's set ups will we break by
> updating and merging this patch? I don't know the answer - it could be a
> handfull or less, which may be worth the 'short term' support cost.
> Maybe its none (one including me?) Or maybe its more? We don't have a
> way to know until they shout angrily ...
>
>

I think realistically most people use libcamera from the distributions
themselves. And in Debian and Ubuntu, libcamera is not updated in
stable releases at all. If people are trying to use updated libcamera
on those distributions, then they are either 1) building from source
or 2) installing a third party build. In both scenarios, handling a
meson upgrade is probably reasonable.

> > folks would benefit from it because it's one less thing depending on
> > essentially unsupported versions of Qt.
>
> I don't disagree. Hence earlier - which is the chicken, and which is the
> egg ...

🤷‍♂️



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