QSettings deleted by singleton-cleanup mechanism

[Daniel J Sebald]

Currently the GUI's QSettings are instantiated and deleted by the Octave 
worker thread using the singleton-cleanup mechanism.  Can that be 
changed?  Was there a reason to have the worker, which is in another 
thread, do this?

According to the Qt documentation:

http://doc.qt.io/qt-4.8/qsettings.html#sync

the QSettings are periodically saved and saved when the object is 
deleted.  It seems to me rather straightforward for the main window to 
create a QSettings object when it is created.  The QSettings will be 
automatically deleted when the main window is deleted and consequently 
save the settings to permanent storage then.  Or, another approach would 
be to create a QSettings locally, save any changes in the QSettings and 
delete the QSettings locally.

The problem with having some other thread save the settings is if that 
thread is interrupted abruptly (say with a force close, which I'm trying 
to fix at the moment), it can remove the QSettings or incompletely save 
settings.

Dan