Make the config editor symlink friendly

[bonecountysheriff]

When you change a setting, lxqt-config seems to delete any existing config, then make a new one, rather than editing the existing config file in place. Even if the file is a symlink, the editor replaces the symlink rather than following it and replacing the file.

I am using a symlink manager (GNU stow) in order to sync my desktop configuration across the devices I use. So the above behavior is a problem.

❯ lxqt-config --version
lxqt-config 0.16.1
liblxqt   0.16.0
Qt        5.15.1

I am testing this on archlinux.

Expected Behavior

Follow the symlink, replace the actual file with the new config file.
Both the initial and the final structure must look like this.

~/.config/lxqt/lxqt.conf -> ~/.dotfiles/.config/lxqt/lxqt.conf (symlink)
~/.dotfiles/.config/lxqt/lxqt.conf (actual file)

Current Behavior

The symlink is being replaced instead.
This is how it looks after the replacement.

~/.config/lxqt/lxqt.conf (new config file)
~/.dotfiles/.config/lxqt/lxqt.conf (old config file)

Possible Solution

Follow the symlink chain, then replace the actual file (either in-place or by replacing).

Steps to Reproduce (for bugs)

1. Change a setting in lxqt-config and save.

Context

Using dotfiles to sync config across linux machines.

System Information

• Distribution & Version: Archlinux, rolling
• Kernel: 5.11.11
• Qt Version: 5.15.1
• liblxqt Version: 0.16.0
• lxqt-build-tools Version: 0.8.0
• Package version: 0.16.1

[palinek]

Well, this should probably be reported upstream as we don't manipulate config files directly but using the Qt's QSettings...

[tsujan]

lxqt-config seems to delete any existing config, then make a new one

lxqt-config or LXQt doesn't; QSettings does.

[tsujan]

As far as I remember, when writing to a config file, QSettings uses QSaveFile, which guarantees not losing data if writing fails (that's especially important on quitting). QSaveFile writes to a temporary file and then moves that file to the original file; hence the removal of symlinks.

[bonecountysheriff]

Alright, thanks for giving me a start.

@tsujan, I just want to confirm.
Is this the file?
https://code.qt.io/cgit/qt/qtbase.git/tree/src/corelib/io/qsavefile.cpp

[tsujan]

Is this the file?

Yes.

What I said was in my memory; didn't check Qt's source. If you want to know exactly what happens, you'll need to read Qt → src/corelib/io/qsettings.cpp and its related files.

Anyway, LXQt doesn't reinvent the wheel. In most places, it uses QSettings, whether directly or indirectly. In a few places — especially in libfm-qt — it uses GLib's GKeyFile, which does the same thing, more or less.

[bonecountysheriff]

Too bad they decided not to go with it.
https://bugreports.qt.io/browse/QTBUG-93085

[tsujan]

I think config files are too important to depend on arbitrary files (symlinks). Although I've seen that Qt devs have sometime made bad decisions, IMO, this isn't one of them: it's the best way of handling config files.

[QiangF]

symlinks seem to work for me now. I am using Arch linux.