Packages that can target either Qt5, or Qt6, but not both at the same time

[hmaarrfk]

Comment:

I got a question from @looooo about how to package a feedstock they cared about for qt6.
conda-forge/soqt-feedstock#18

This kinda brought up some issues I've had on OpenCV.

In short:

• It would be desirable to provide a flag to allow users to install the package for qt6.
• The library can be built with qt5, or qt6
• We would like to prefer the version of qt that the user currently has installed. that is qt-main or qt6-main, but we would like to avoid having to install a new version of qt if one of them is already present

Is there a way to achieve this with the current semantics?

Do we need a CONDA_QT or __qt metapackage?

List of packakges

• opencv supports qt6
• paraview supports qt6 in 5.12
• soqt supports qt6 on master development branch

[jschueller]

I dont know if its possible.
But if both are available, does conda pick the one matching with the qt version already installed ?
Do we have a list of qt packages somewhere ? Maybe we can assess the status of each to see if all can be migrated to qt6, for example I know paraview 5.12 will support qt6.

[hmaarrfk]

But if both are available, does conda pick the one matching with the qt version already installed ?

conda ends up picking a random one (or the one with the higher build number), since for all it knows the packages are pretty much equivalent.

[hmaarrfk]

Trying to address this:
conda-forge/staged-recipes#25688

[jschueller]

Maybe we should try to begin switching to qt6 ; I already moved paraview
are there still packages left that can only target qt5 ?

[hmaarrfk]

Spyder. Needs qt webengine

And napari, pyside6 still causes some segfaults

[hmaarrfk]

Do we have pyqt6 yet? I couldn't find a package. that one might be critical for some projects like spyder.