[Interest] [Development] Qt 6.5 Is Irrelevant for More than 95% of Mac Desktops

[Tuukka Turunen]

Hi,

Most of the macOS users are quite quick to take on new OS versions and this is true also for adoption of macOS versions with the new numbering scheme. Apple hardware is also rather good in keeping support for new OS versions and at least between versions 10.15 and 11 there does not seem to be a major drop in what HW is supported.

The challenge we have with supporting macOS versions is that some users migrate really quickly, so we need to work a lot with the unreleased (developer beta) versions in order to ensure Qt works well with the new macOS version optimally before it is even released for production. We also aim to keep supporting older versions and the ones in between. This means quite a lot of CI system load – especially as we now have both Intel and ARM architectures to test on.

There is also positive development happening. With the latest versions the virtualization support is improving so that we are hopeful to be able to use the hardware more efficiently (by running two virtual machines in each physical HW). So while macOS is still far from the convenience we have with Linux and Windows that support sever grade hardware, things are getting better with Macs as well going forward (not for 10.15, though).

Related to the usage of 10.15 one indication comes from Creator telemetry. Based of this roughly 8% of the macOS users this year have version 10.15. Of course, this is not a direct indicator for how many end users of Qt based apps there are with macOS 10.15, just how much of the developers using Creator have it. Telemetry is fully optional, but I think it is reasonable accurate for this type of data point as the OS version is unlikely to greatly affect sending or not sending the telemetry data. Note also that we have a lot of different Qt versions supporting macOS 10.15, and many applications are still using Qt 5.

Yours,

                Tuukka

From: Interest <interest-bounces at qt-project.org> on behalf of Thiago Macieira <thiago.macieira at intel.com>
Date: Saturday, 17. December 2022 at 1.20
To: development at qt-project.org <development at qt-project.org>, interest at qt-project.org <interest at qt-project.org>
Subject: Re: [Interest] [Development] Qt 6.5 Is Irrelevant for More than 95% of Mac Desktops
On Friday, 16 December 2022 18:15:11 -03 Alexander Dyagilev wrote:
> But why did you do this? Does the supporting of 10.15 really increase
> the development cost for Qt Company?

I can't speak for the Qt Company costs, particularly for the fact that this is
one of their LTS releases.

But in general, it does increase the costs overall. There are new APIs that we
can use if we don't have to keep 10.15 compat, there's one fewer platform to
test on (usually with a virtual machine) before release, and so on. The
benefits may not be realised now, but they will come in the future.

For me specifically, what matters is that 11.0 dropped support for Intel Macs
that don't have AVX2 support, meaning that I can now assume that all machines
running Qt 6.5 natively have it. We had further changes based on this
assumption ready to go for 6.5, but they got removed at the last minute due to
unexpected side-effects and the feature freeze being too close.

On Friday, 16 December 2022 19:44:16 -03 Michael Jackson wrote:
> I agree here. Is Qt 6.5 now using an API or a compiler feature that macOS
> 10.15 does not support?

As of *today*, no. This may change tomorrow, as developers continue to do
their work. That means that, as of *today*, Qt 6.5 *could* be compiled to run
on 10.15, by just lowering the default minimum version somewhere in a config
file. But we are not promising that this will remain true and especially we are
not testing that it works.

We had to make a call and following Apple's own support lifetime makes sense.
If you want to stay on an OS that is not receiving important fixes, then you
can also stay on a Qt that is not receiving fixes. Though unlike Apple, you can
backport fixes to 6.4 yourself or remove the new requirements from 6.5 yourself
(or contract someone to do it for you).

Moreover, there's a time delay. This affects Qt 6.5, which will be released in
March 2023, which means it probably affects applications released in May 2023
and later.

>  Is there a security library that Qt 6 depends on (OpenSSL is my guess) that
>  10.15 isn't now updating? Is Qt 6 using the new APIs from that version of
>  OpenSSL (or what ever library broke)? Is there a graphics API that Qt 6
>  now depends on that is macOS 11.0 and greater? Maybe that is the reason?

Any of the above or others may become another reason. The point is that we
need to officially drop the platform first, before we can depend on and require
some of those APIs. It's not the other way around.

--
Thiago Macieira - thiago.macieira (AT) intel.com
  Cloud Software Architect - Intel DCAI Cloud Engineering



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