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

[FERRATON Alain (Adjoint au chef de groupe) - SG/DNUM/MSP/DS/GSG]

Hi Denis, 

Thanks for your feedback. 

I think that re-introducing backwards compatibility in QGIS 3.28 would
be valuable for our services. The size of the project files is not too
critical in my opinion compared to the size of the data files, which are
usually much larger. 

Is this possible for QGIS 3.28.7? 

Alain

---
Alain FERRATON

Adjoint au chef de groupe
MSP/DS/GSG
Direction du numérique | Secrétariat général 

MAN 7, rue René Viviani 44200 NANTES
Bureau : MAN étage 1 plateau B
Tel : +33 240128408 - Mobile : +33 671794593
www.ecologie.gouv.fr [1]

 		Secrétariat général

 MINISTÈRES
TRANSITION ÉCOLOGIQUE
COHÉSION DES TERRITOIRES
TRANSITION ÉNERGÉTIQUE
MER 

Le 28/04/2023 10:02, > denis.rouzaud a écrit :

> 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
>> Bureau : MAN étage 1 plateau B
>> Tel : +33 240128408 - Mobile : +33 671794593
>> www.ecologie.gouv.fr [1]
>> 
>> Secrétariat général
>> 
>> MINISTÈRES
>> TRANSITION ÉCOLOGIQUE
>> COHÉSION DES TERRITOIRES
>> TRANSITION ÉNERGÉTIQUE
>> MER 
>> 
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Links:
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