[QGIS-Developer] QGIS 3.46 builds to use Qt6?

[Julien Cabieces]

Hi,

I'm also in favor of switching to Qt 6 builds and the timeline you
propose Martin seems reasonnable to me.

However, I think we should increment the QGIS major version to 4.0 in order
to stongly advertise our users and plugin developers that there is an
API break. If we are not doing now, when do we plan to increment the
major and clean the code from all deprecated content?

Regarding the proposal of having 2 versions (Qt 5 and Qt 6), I'm not
completely sure this is a good idea. I'm afraid that plugin developer
would delay the plugin migration if this is still possible to run a QGIS
with Qt 5. It also muddy the download process for users with a technical question (Qt 5 or 6) he
is not fully skilled to answer.

I would be more in favor of clearly state that the last version (3.46 or
4.0) is not able to run non migrated plugin and if you're using this
plugins, you should stick to the previous one. It would also be
interesting to display on the plugins platform which are compatible with
Qt 6 and which are not.

Regards,
Julien



> On Tue, 17 Dec 2024 at 10:48, Greg Troxel via QGIS-Developer <qgis-developer at lists.osgeo.org> wrote:
>
>> I wonder about "less stable" qt5 and "more stable" qt6.  Do we really
>> believe that qgis built on qt6, with no plugins will have fewer crashes
>> and quirks, than the qt5 build?
>
> Yes, I do. Because Qt 5 is not improving any more, but Qt 6 is. An example would be when running under Wayland environments on
> linux -- it's a very broken mess on Qt 5 and will never be fixed. On Qt 6 it's only a slightly-broken mess, and will likely be non-broken within
> the next 12 months. There's a similar situation for apple processors, which never had full official support on Qt 5 but ARE fully supported
> on Qt 6. This gap is only getting wider as newer operating system updates and corresponding changes break things underneath Qt 5.
>
> There's also a limited stream of bug fixes getting ported back to Qt 5.15, vs those flowing into the supported Qt 6 releases.
>
>>  That is surprising to me at this point.
>> Do we still believe that if one assumes "qgis with N random plugins that
>> claim to support qt6"?
>
> (Well, QGIS + **ANY** plugin = a less stable QGIS. 🤣 But that's a completely different point)
>
>> I expect a qt6 build is kind of like a .0 release, and we would want to
>> have qt6 builds widel avaialable and time for feedback before saying
>> it's stable.
>
> I'd say we're well past the ".0" stage of Qt 6 support. Almost all the core functionality is quite well tested at this stage, and third party
> clients (like Mergin and QField) switched to Qt 6 based QGIS builds earlier this year. I'm confident that by the time we hit a (potential)
> October 2025 milestone that we'll have a very stable Qt 6 build available.
>
> Nyall
>
>>
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-- 

Julien Cabieces
Senior Developer at Oslandia
julien.cabieces at oslandia.com