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

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

Hello all

A polygon layer saved in a project file with QGIS 3.28 systematically
opens in blue in QGIS 3.16 (style is lost).

There has been a change in the way style is saved in project files
introduced in QGIS 3.22.

QGIS 3.22 seems to save the style in both formats (<Opt (<Option.../>)

and <prop k=.../>)

(see attachment)

This is no longer the case in QGIS 3.28.

We have a heterogeneous QGIS version park. The lack of style backward
compatibility is a major constraint on the gradual migration of our
services to QGIS 3.28.

We could consider developing or having a plugin developed to provide
this backward compatibility.
Is this possible? What would be the best way to go about it? Can we find
documentation on storing styles in QGIS project files and their
evolution?
(I haven't found anything on the web).

A possible solution might be to automate the QGIS 3.28 -> QGIS 3.16
conversion using QGIS 3.22.
What do you think about this? What is the best way to do it?

Best regards

-- 
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

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TRANSITION ÉCOLOGIQUE
COHÉSION DES TERRITOIRES
TRANSITION ÉNERGÉTIQUE
MER 

 

Links:
------
[1] https://www.ecologie.gouv.fr
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