[QGIS-Developer] Backward compatibility for style in project files between QGIS versions

[Denis Rouzaud]

Hi Alain,

Yes, the backward compatibility to 3.16 has been removed in 3.28,
considering there was a LTR in between and that 3.16 was not maintained for
more than a year.

The PR is here https://github.com/qgis/QGIS/pull/45143

I am not sure if it's possible to do it with a plugin.
An approach would be to revert this in the 3.28 branch to give more time. I
have no strong opinion here. The main motivation to drop compatibility was
the size of the project file and redundancy of information (manually
editing the file gets harder).

Denis


Le jeu. 27 avr. 2023, 09:08, FERRATON Alain (Adjoint au chef de groupe) -
SG/DNUM/MSP/DS/GSG via QGIS-Developer <qgis-developer at lists.osgeo.org> a
écrit :

> Hi
>
> A polygon layer saved in a project file with QGIS 3.28 is systematically
> opened in blue in QGIS 3.16 (the style is lost).
>
> There has been a change in the storage of style in project files
> introduced in QGIS 3.22.
>
> QGIS 3.22 save the style in both formats (<Option.../>
>
> and <prop k=.../>
>
> (see the attachment)
>
> This is no longer the case in QGIS 3.28
>
> We have a heterogeneous QGIS version park. The non backward compatibility
> of style is an important brake to migrate progressively our services to
> QGIS 3.28
>
> We could consider developing or having developed a plugin to ensure this
> backward compatibility.
> Is this possible? What would be the best way to proceed? Can we find
> documentation on the storage of styles in QGIS project files and on its
> evolution?
> (I didn't find anything relevant by searching on the internet).
>
> Sincerely,
> --
>
> *Alain FERRATON*
> Adjoint au chef de groupe
> MSP/DS/GSG
> Direction du numérique | Secrétariat général
>
> MAN 7, rue René Viviani 44200 NANTES
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