Hi PSC, devs, I'd like to kick start some discussion on how best to handle the situation with upstream Qt and their (lack of) support for Qt 5. As a quick summary of the situation:
- Qt Co effectively ended open source support of Qt 5 at the 5.15.2 release, and have moved all focus to Qt 6. - While some preliminary work has been done, QGIS doesn't currently support Qt 6 based builds, and likely won't be ready for this for some time (even completely ignoring all the stable API questions a Qt 6 build raises entirely!) - QGIS often depends on fixes and enhancements which need to be made upstream in Qt, and can't be resolved or worked-around in QGIS alone - KDE and other open source projects forked Qt 5.15 at https://invent.kde.org/qt/qt/qtbase/-/commits/dev/, and are actively backporting fixes from Qt6 to that branch. Fedora recently started using the KDE branch for Qt 5 library builds, so users of that platform once again are getting bug fixes deployed [1]. I'm unaware if other distributions or builds of Qt are using this currently. - Similarly, there's a KDE fork of Qt 3d at https://invent.kde.org/qt/qt/qt3d/-/commits/kde/5.15/ Right now, there's a number of very frustrating issues that Qt 5.15.2 has which impact our users. An example is #44876, which results in very large PDF exports from QGIS with broken hairline line rendering [2]. In the past QGIS has contracted KDAB as part of the QGIS bug fixing efforts to directly fix issues which affect QGIS users upstream, with good results. Unfortunately, given that we are stuck on Qt 5.15.2 and upstream won't release any more 5.15.x versions, we can't just do that same approach again to get fixes into Qt. So I'd like to raise discussions about the best way we can handle this situation as a downstream project. My thoughts/questions: - Are we free to change the Windows builds to use the KDE backports fork of 5.15 instead of the official 5.15.2 releases? (Or does that change lots of osgeo4w packaging things?). Similarly, are we free to move the MacOS builds to the KDE branch too? - Could we also move the Windows/MacOS builds of Qt 3d to use the KDE fork? - Does anyone know if Debian have plans to migrate to the KDE backports fork? (Last I heard, the debian Qt maintainers stepped down and the package is currently lacking a maintainer!) - If we can get the majority of our users onto builds which use the KDE backports branch (i.e. Windows/mac users), could we re-start the relationship with KDAB and contract them for bug fixes again for 3.22? (with the arrangement explicitly requiring them to backport fixes to Qt 5 via KDE's fork). Nyall [1] https://src.fedoraproject.org/rpms/qt5-qtbase/c/400d49b3925dc2852218289310674abd3950b4e0?branch=rawhide [2] https://github.com/qgis/QGIS/issues/44876 _______________________________________________ QGIS-Developer mailing list [email protected] List info: https://lists.osgeo.org/mailman/listinfo/qgis-developer Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-developer
