qutebrowser: downgrade Qt to 5.14

[rnhmjoj]

Motivation for this change

There are a number of unresolved issues with Qt 5.15, the most
important one being the inability to properly restore sessions1.
For now it's better to stay at the earlier version.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using (qutebrowser)
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

[woffs]

This is related to #97586 2daf570 #98885 and others. I'm fine with 5.15, but as long as qutebrowser has issues with 5.15, it may be better to run under 5.14. This patch works.

[rnhmjoj]

Backport: 3bef864

[The-Compiler]

FWIW other than the session support, I think all of those issues are either fixed in Qt 5.15.1 (or .2), or just not relevant outside of qutebrowser development. The only other remaining issue with Qt 5.15.1 are renderer process crashes which can be fixed by backporting this patch: [Backport] Fix for bug 1071327 (Icf418990) · Gerrit Code Review

As for the session support, the choice is between being able to fully restore sessions or having security patches:

• Qt 5.14.2: Based on Chromium 85.0.4183.83 (~2019-10-10) with security patches up to 80.0.3987.132 (2020-03-03)
• Qt 5.15.1: Based on Chromium 80.0.3987.163 (2020-04-02) with security patches up to 85.0.4183.83 (2020-08-25)

IMHO, for a web browser, lagging behind more than absolutely necessary with security patches is a bigger problem than not getting back-/forward history after restoring sessions.

[rnhmjoj]

Hi, thank you for chiming in. I didn't most of the issue were already resolved, I'll take a look at the patch and consider porting it.

[FRidh]

Intention to "revert" to 5.15 in 902c567 as part of #99956.

[doronbehar]

I'm working on a PR to add that patch to our qt5.15

[doronbehar]

qtwebengine PR: #100041