ubuntu-app-platform updated to Qt 5.6.2

[Timo Jyrinki]

2017-01-31 10:23 GMT+02:00 Alberto Mardegan <alberto.mardegan at canonical.com>:
> Do we have a clear understanding of why this happens? Qt apps are
> supposed to be binary compatible against newer releases.
> One exception could be if the app itself is shipping some plugins,
> because in that case I believe that these plugins are somehow bound to a
> specific Qt version.

Yes, it seems snaps like ubuntu-terminal-app and dekko ship their on
Qt version which should not be the case when the platform snap is
used.

Qt detects loading of modules with different versions and throws the
error message. Technically we could patch Qt to not do this maybe over
enthusiastic detection (Qt 5.6 point releases should naturally be 100%
forward and backward compatible sans fixed bugs), but then again it's
good that we detected these extra libraries being shipped.

> And I wonder, maybe we should think of a different versioning scheme for
> the interface? Otherwise, we should have a documentation page which maps
> the snap version numbers to the Qt version contained within them.

I think it's ok for now to keep the version "1" in the content field
and not introduce a new package version or a package rename. I
understood there are new features in development that could allow
multiple releases to be available from the store at the same time, and
maybe that would mean that package requiring content:
ubuntu-app-platform1 could continue to get the last one with that
version while developers could move to ubuntu-app-platform2 when such
is decided to be released eventually.

> Given that Qt is at the core of ubuntu-app-platform and that a change of
> the Qt version is something we want all developers to be aware of, maybe
> the snap (and the "content" interface field) should contain also an
> indication of the Qt version they provide?

The platform snap's description does contain the version of Qt
included. However, the snap also contains lots of other libraries and
more transparency would be useful. Certainly some documentation will
be needed.

-Timo