Make the Ubuntu build with Qt6 successfully and easily

[tai271828]

Update

Ubuntu 22.04 (Jammy Jellyfish) is expected to ship with qt6 so this thread should not be an issue unless we would like to support qt5 in earlier Ubuntu versions.

# rmadison libqt6core6
 libqt6core6 | 6.2.2+dfsg-6ubuntu2 | jammy/universe          | amd64, arm64, armhf, ppc64el, riscv64, s390x
 libqt6core6 | 6.2.4+dfsg-1ubuntu1 | jammy-proposed/universe | amd64, arm64, armhf, ppc64el, riscv64, s390x

Original Description

So far building with Qt6 is not a must but a bit pesky for Ubuntu users. Is it worthy to make a better build experience for Ubuntu users? Not limited to modmesh itself, for example, add build scripts to devenv to include the expected Qt configuration and libs?

This topic is inspired by this issue.

[yungyuc]

Why building with Qt is an issue on Ubuntu?

[tai271828]

Ah, I should have said "build with Qt6". I updated my description and the thread title.

Currently debian/ubuntu (and their package archive) does not ship with Qt6. Build Qt6 from source for debian/ubuntu users seem essential.

[yungyuc]

jammy seems to have qt6 being packaged and it will be released later this month. That might be an option for Ubuntu users who do not want to build from source.

It might be an option to back-port the code to use Qt5. I am not sure how easy it is, though. I just started to learn Qt(6).

[tai271828]

Oooops! You are right. The package is in the "universe" repository and I missed to check it. My bad.

If qt6 is available in Jammy and I think it is good enough because Jammy is a LTS.

I don't think we need to back-port to use Qt5 unless we urge to have this feature in Ubuntu 20.4 (Focal Fossa).

[yungyuc]

If you have not been able to make it run, perhaps #61 can help you.

[tai271828]

fwiw, Ubuntu 22.04 (Jammy) is able to build modmesh with Qt6 lib enabled. #28 (comment)

[yungyuc]

Please use cmake to build and try again. Do not use setup.py. The problem is that setup.py can only build Python extension module. However, the viewer is an application embeds Python interpreter. It is not a Python extension module.

You can find how to use cmake in the root Makefile. setup.py was only created to make package manager happy with the Python extension module part.

[tai271828]

make viewer works. Now ./modmesh/cpp/binary/viewer/viewer will show up!

[tai271828]

The viewer binary is launched. However, when clicking run, I got

$ ./modmesh/cpp/binary/viewer/viewer
Loading _modmesh_view ... succeeds
Loading modmesh ... succeeds
AttributeError: module 'modmesh' has no attribute 'StaticMesh'

At:
  <string>(6): make_2d
  <string>(29): <module>

I will check my build environment variable to figure if it is a bug or my environment issue.

[yungyuc]

This seems to be a symptom that you only build the viewer target but not the buildext. The viewer needs both to work. This may use an enhancement in the embedded Python code, but at the time being building both targets works around it.

[tai271828]

Thanks for the tip @yungyuc . make buildext does help. Now the viewer and REPL work for me ...via ssh X forwarding! I think my next step will be finding out a local machine shipped with Qt6 lib to make my development environment friendly if I would like to participate the viewer development further.

Nevertheless, I would like to prioritize my task to be 1) #75 and then 2) #28 first. Let me back to the Qt6 lib in my Linux distro issue later.

[tai271828]

Jim told us that we can download qt6 deb here (by filling your contact information) https://www.qt.io/download