[Development] Windows 7 support will be dropped in Qt 6

[Edward Welbourne]

Edward Welbourne wrote:
>> If we *never* allow ourselves breaking changes, we'd still have a
>> nice stable product that worked great on an O/S or two from the last
>> century.  Qt would thus be irrelevant.

Kevin Kofler (16 June 2020 01:36)
> Nonsense. We would have a nice stable product that just works on old
> and new operating systems alike. New operating systems are either
> supported out of the box thanks to backwards compatibility, or support
> can be added without any breaking changes.

Oh yes, we could indeed have a product with a last-century feature-set
that still works on all the legacy operating systems and is completely
irrelevant on any modern operating system where that feature-set would
utterly fail to live up to the expectations of users of those more
modern operating systems.  Qt would still be irrelevant in this case.

So my bad, I said our product would only work on an ancient O/S or two,
when it could indeed to made to work on a whole bunch of more modern
systems *on which it would be irrelevant* - and thus not worth the
significant effort of porting to, because anyone developing apps for
those newer systems would look at our feature set and decide to use
something that actually makes good use of the shiny new features of the
O/S they're targeting.  So, same difference, sorry about phrasing it
from the premise that no-one would bother porting to a newer O/S that
makes the twentieth-century feature-set archaic and worthless.

> Supporting a new operating system version does not require dropping
> support for older versions, and most definitely does not require the
> other (entirely unrelated) breaking changes (deprecations etc.) that
> are being implemented in Qt 6.

Sure, supporting new operating system versions doesn't require dropping
support for older ones; but adding new features that make good use of
what the new operating system offers - that the old did not - and
enables developers to write apps that integrate with other things on the
new system - in ways the old did not support - is necessary if your
framework is to actually still be relevant in a few years' time, when
making the most of what the O/S of the day offers is required if you're
to be of any real use to the developers of new apps.  If you stop being
relevant to those developers, the time until you become irrelevant has
started ticking down.

In particular, where an old O/S doesn't support some feature present in
a newer O/S, a cross-platform toolkit that tries to provide the same
features everywhere is left with an uncomfortable choice between
kludging together for the old system some kind of emulation of what the
new provides, or having a limited feature-set on the old system.  At
some point - instead of claiming to be cross-platform but failing to
have the full feature-set on a nominally supported platform, while also
supporting a mess of kludges to implement, for that platform, features
every newer the O/S provides for us - it becomes more sensible (and more
honest) to own up to not really supporting that platform any more.

>> Just had a quick look at that issue [QTBUG-74687]; and I note that it
>> *didn't* ask your opinion, it set out to evaluate how practical it
>> would be to drop Win 7.

For reference, the actual title is: "Investigate effort/pros/cons of
discontinuing Windows 7 support in Qt 6 [Spike]".  Which I imagined you
knew, since you first mentioned the bug, so forgive my paraphrase, I
didn't see the need to repeat such a long title.

> Huh? How do you "evaluate how practical it would be to drop Win 7"
> WITHOUT listening to those who would actually be affected by it?

While evaluation of the pros and cons does involve garnering information
about how users shall be affected, the means of doing that is not - nor
should it be - having the highly self-selecting group of folk who notice
the evaluation task "vote" on whether it's worth it or not.  A broader
overview of users is required, without the *huge* bias against change
that this would entail.  Better for those working on the issue to
consult sales and product managers, who routinely talk to a somewhat
broad cross-section of users.  Not a perfect sample, but statistically
less biased than those watching Jira closely enough to notice this
task.  To be sure, "some folk aren't going to like this" is one of the
cons, and surely was taken into account as such; but that gets to be
balanced against the diverse pros - notably including: deleting old code
that's specific to one platform reduces maintenance burden.

So sure, we need to listen to those who'll be affected; but we need to
listen to a broad cross-section of those affected (including those who
aren't using Win 7 any more and would only gain the benefits of our
development effort not being spread as thin as they would be while still
trying to support Win 7 - and probably only partially support it at that,
due to not managing to work out how to implement, on it, some of the
shiny new things we're adding at Qt 6).  In particular, those given this
evaluation task should not listen to "whoever shouts loudest and in
their face" in preference to the many other users out there.

	Eddy.