[Interest] Best practices for settings

[Philipp Kursawe]

> The mechanism to be notified would be different depending on where the
settings are stored.  E.g. if they are stored in a file, you could try
using a QFileSystemWatcher (although I haven't tried that myself), but you
still wouldn't know > which setting changed.  (Although maybe
QConfFileSettingsPrivate::syncConfFile is in a position to emit signals for
each changed property, it doesn't.)  Whereas I think Windows has a more
fine-grained way of notifying about > registry changes.  So you could argue
that Qt should abstract it… but adding features to QSettings (or even
fixing bugs) is unpopular because of its design flaws.  The biggest problem
is that the API is stateful, with begin/end setters > to control which
section you are looking at, etc.  That can also be fixed in your subclass
or wrapper, at a cost in performance: pass the section name to each
accessor, so the accessor will do the beginGroup, read/write setting, >
endGroup.

As you say, this would not allow to participants to know which setting
changed, only that some settings changed. Under Win32 there is a way to
monitor registry changes, yes. But what of you are using ini files, as we
do?

Of course we could make the policy, that whoever changes a setting needs to
post an event to QApplication.
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