Agreed. I really think that we can drop the default-settings file and then can run octave with a non-readable/writable settings file. But this is not really highest priority.

> I don't think having a non-writable qt-settings should make Octave inoperable.

I agree with that. I discussed with Torsten on another bug report (bug #52090) about trying to make the GUI less dependent on the default settings being set correctly, use default values declared in a single place in the code, and not break if the settings file is unreadable or can't be created for any reason.

Do you want to make this bug be about that?

I have known about this for quite a while, and IMHO I don't see anything that Octave needs to fix. Obviously if someone runs a program as root, and HOME is set to your user's home directory, then some files may be created owned by root.

Ideally, if you actually do run Octave as root, then you would be sure that HOME is set to /root, with 'sudo -H' or 'sudo env HOME=/root octave --gui'.

I was testing some installation issues (Documentation QHC) and ran Octave using "sudo" to see if the feature would work correctly and where a hidden directory goes to.  In the process, I discovered that doing this writes a settings file that is owned by root:

sebald@linux ~/octave/bug/53006 $ ls -la /home/sebald/.config/octave/qt-settings -l
-rw-rw-r-- 1 root root 46722 Mar 29 12:01 /home/sebald/.config/octave/qt-settings

Subsequently, on a follow up non-sudo launch Octave complains

Octave Critical Error

The settings file
/home/sebald/.config/octave/qt-settings
does not exist and can not be created.
Make sure you have read and write permissions to
/home/sebald/.config/octave

Octave GUI must be closed now.

Two things about this are

1) This shouldn't be a critical error, but perhaps put up a warning dialog that settings will be default (can't read) and will not be saved (can't write).  However, I know that this is a critical error, because Octave GUI docked-widget/float-window will use the settings file as an intermediate storage area.  Hence, Octave GUI can't possibly function.  On the other hand, I've recently created a changeset

https://savannah.gnu.org/bugs/?53276

that doesn't use the settings as in intermediate (i.e., save then read), but instead only saves to settings and keeps an internal record of both docked and float positions.

2) There should be special care about writing settings files that are of different ownership than the original settings file.  Either don't overwrite, or put up a dialog box at exit (or wherever) warning about the overwrite and whether Octave should do so.