[SailfishDevel] qt upgrade

Martin Kolman martin.kolman at gmail.com
Sun Feb 10 20:56:41 UTC 2019

Sun, 10 Feb 2019 09:56:06 +0200 Rinigus <rinigus.git at gmail.com>:
> Morning,
> suggestion to consider Qt 5.12 in /opt comes from the following:
> * newer web engine
> * we can use and contribute to the code written for Plasma with its 
> Kirigami
> It will not bring native new applications, we don't have Silica for 
> it. However, I personally think it makes more sense to use and help 
> out with the development of Linux-based solutions than to use 
> Android-provided web browsers through SFOS Android compatibility layer.
> This would not to be intended to be installed in /usr and having 
> platform supporting multiple Qt versions at once. I have no idea 
> whether its possible and no desire to get into messing up the system 
> layer.
> Dmitriy: I don't know whether you can mix different Qt versions in the 
> same application. In this respect, yes, you could probably ship Qt 512 
> stack fully, but would probably have to stay away from the 
> system-provided Qt.
> Leszek: fragmentation is to be considered, indeed. But, as far as I 
> understood, it makes sense to develop browser against the last version 
> of Qt. In some aspect, using Qt59 on SFOS contributes to fragmentation 
> in a way that we, on SFOS, will be using the version that is slowly 
> phased out already. At present, Kirigami is developed using Qt512, 
> with Qt511 version having at least one bug that will never be fixed. 
> Not sure whether Kirigami runs against Qt59. So, if we would like to 
> run Kirigami apps, Qt 5.12 is most probably needed.

I hope eventually support for using Flatpak for package distribution is 
added to Sailfish OS, as that would make it possible to decouple the 
"system" Qt version from the "application" Qt version. Updating the 
system version would not longer risk breakage in third party 
applications and could be done on it's own, likely slower, pace. On the 
other hand updating the "application" Qt would mean just releasing a new 
Flatpak runtime with the updated Qt version. Old application would 
continue working with old runtime/-s while new apps would be able to use 
all the new goodies available via the new runtime. IIRC this is already 
being done for Qt on the desktop via the Flatpak runtimes maintained by 
the KDE project.

Of course there are some trade-offs and things to consider - you would 
have to, in some capacity, maintain multiple versions of Qt and system 
libraries in parallel. On the other hand, each Qt version would be 
either a "system" only one or "application" one. Not one that needs to 
be perfect or else both the system and apps will stop working. This 
could help to reduce the maintenance burden somewhat.

Also, even if it would be nice to keep all older runtimes around so that 
all old (and likely abandoned) apps continue working, it would be likely 
prudent to stop maintaining old runtimes after a while to keep the 
maintenance burden reasonable.

There is also a question if this is something that community can at 
least start or Jolla involvement is needed. As already mentioned in the 
thread, due to Silica still being closed source a community only Flatpak 
effort likely could not support running Silica applications. A Jolla 
provided runtime - or open source Silica - would be needed for that.

> Cheers,
> Rinigus
> On Sun, Feb 10, 2019 at 8:55 AM Dmitriy Purgin <dpurgin at gmail.com 
> <mailto:dpurgin at gmail.com>> wrote:
>     Hi all,
>     if there are some parts of the newer Qt you need in your app, you
>     can always compile it yourself, link your app against the newer
>     version and ship these libraries with your app.
>     Cheers
>     Dmitriy
>     On Sat, Feb 9, 2019 at 6:44 PM rinigus <rinigus.git at gmail.com
>     <mailto:rinigus.git at gmail.com>> wrote:
>         Hi,
>         sounds like there are porting and licensing issues on the way
>         of getting qt 5.9 for SFOS (see logs from the last
>         #mer-meeting). Its all understandable, but it would be great
>         to get a way forward. Not sure whether it has been considered
>         by others and I wonder whether we can make a separate Qt 5.12
>         packages for /opt/qt512?
>         From a quick test, it is possible to run non-silica
>         applications as well (tested with qmlscene and QML with plain
>         Window). In that test, even keyboard worked as expected. Look
>         was non-native, but let it be for now.
>         So, I wonder, whether its possible to get Qt 5.12 compiled
>         with /opt/qt512 prefix and then use it for development using
>         the latest libs (new web browser?) and collaborate with other
>         mobile Linux'es out there. As far as I remember, Wayland was
>         rather old and, maybe, it will preclude Qt 5.12 compilation.
>         @mal, though, had a newer version around and it may serve a
>         purpose for such project. Is there anything else that should
>         be considered?
>         Cheers,
>         Rinigus
>         PS: Please consider it as request-for-comment and not as any
>         kind of statement nor call-for-action :)
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