qownnotes: build with Qt6

[totoroot]

Description of changes

• Build qownnotes with Qt6

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 23.05 Release Notes (or backporting 22.11 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

[pbek]

You can drop qtxmlpatterns altogether, I removed the need for that dependency when porting the app to Qt6.

[totoroot]

Rebased onto master after version update got merged.
Removed dependency qtxmlpatterns.

[SuperSandro2000]

@SuperSandro2000 Can you please review and let me know whether adding support for Qt6 like this is alright? Per default qownnotes would still be built using Qt5.

Why do we need both options? If qt6 just works, we can only offer that.

[pbek]

@SuperSandro2000 Can you please review and let me know whether adding support for Qt6 like this is alright? Per default qownnotes would still be built using Qt5.

Why do we need both options? If qt6 just works, we can only offer that.

Yeah, I was asking the same in #227301 (comment).
Would there be an advantage in keeping both, e.g. Better integration or disk space?

[totoroot]

I saw this merged PR and the comment by @peterhoeg and thought that Qt6 might not be usable for some, so I wanted to be on the safe side like they did with zeal.

If there is no advantage in keeping both, then I will happily adapt the PR to only use Qt6.

[pbek]

And 32bit isn't supported by Qt6 any more...

The issue with qt6 is that the applications look like crap under KDE because the theme isn't picked up automatically.
#202103 (comment)

Yes, I feared as much.
In KDE Neon I had no UI issues with the Qt6 version of QOwnNotes.

[pbek]

qownnotes-qt6 builds and works nice. I coudn't find any issues.

[wegank]

Needs rebase at least.

[totoroot]

Since the consensus seems to be that there is no real problem in moving to building with Qt6, I changed the PR to only build with Qt6.
I guess we'll see whether someone complains about this move breaking something.

On NixOS with KDE Plasma QOwnNotes built with Qt6 looks just fine. I've also successfully built it on x86_64-darwin, and the only issue I've seen, is that the title bar is not adapting to my dark system theme, but I guess that's manageable.

[totoroot]

Not relevant to this PR, but I'm getting a bunch of warnings like this for these two plugins.

Warning: In /nix/store/milahyvgak2ym1d5hk2zyl7pbljljjs7-qtwayland-5.15.8-bin/lib/qt-5.15.8/plugins/wayland-shell-integration/libwl-shell.so:
  Plugin uses incompatible Qt library (5.15.0) [release] ((null):0, (null))   nqqjc2vn-systemd-253.3-dev
...
Warning: In /nix/store/milahyvgak2ym1d5hk2zyl7pbljljjs7-qtwayland-5.15.8-bin/lib/qt-5.15.8/plugins/wayland-graphics-integration-client/libxcomposite-glx.so:
  Plugin uses incompatible Qt library (5.15.0) [release] ((null):0, (null))   1.29-dev/include -I/nix/st

@pbek are you aware of this?

[totoroot]

Result of nixpkgs-review pr 227301 run on x86_64-linux 1

1 package built:

• qownnotes

[totoroot]

Result of nixpkgs-review pr 227301 run on x86_64-darwin 1

1 package built:

• qownnotes

[wegank]

Result of nixpkgs-review pr 227301 run on aarch64-darwin 1

1 package built:

• qownnotes

[wegank]

Not relevant to this PR, but I'm getting a bunch of warnings like this for these two plugins.

Warning: In /nix/store/milahyvgak2ym1d5hk2zyl7pbljljjs7-qtwayland-5.15.8-bin/lib/qt-5.15.8/plugins/wayland-shell-integration/libwl-shell.so:
  Plugin uses incompatible Qt library (5.15.0) [release] ((null):0, (null))   nqqjc2vn-systemd-253.3-dev
...
Warning: In /nix/store/milahyvgak2ym1d5hk2zyl7pbljljjs7-qtwayland-5.15.8-bin/lib/qt-5.15.8/plugins/wayland-graphics-integration-client/libxcomposite-glx.so:
  Plugin uses incompatible Qt library (5.15.0) [release] ((null):0, (null))   1.29-dev/include -I/nix/st

@pbek are you aware of this?

This is not specific to qownnotes, see #227795.

[pbek]

Thank you!

[pbek]

I got similar (but different) warnings:

[08:52:26] [warning] In /nix/store/dlqrinrvpw234k2q1hsb5x4y0k90jw46-qtdeclarative-5.15.8-bin/lib/qt-5.15.8/qml/QtQml/Models.2/libmodelsplugin.so: Plugin uses incompatible Qt library (5.15.0) [release]
[08:52:26] [warning] In /nix/store/dlqrinrvpw234k2q1hsb5x4y0k90jw46-qtdeclarative-5.15.8-bin/lib/qt-5.15.8/qml/QtQml/WorkerScript.2/libworkerscriptplugin.so: Plugin uses incompatible Qt library (5.15.0) [release]