Delay initialization of the UserPreferencesManager.

[rhwood]

Allow the InstanceManager to initialize the default instance of the UserPreferencesManager after it has created the default instance.

Fixes #3999.

The problem here was that, in the absence of per-profile/per-computer stored user preferences, and in the presence of the older-style per-profile/all-computers stored user preferences, creating and initializing the default instance before registering it was causing the infinite looping. The solution was to implement the InstanceManagerAutoInitialize interface for JmriUserPreferencesManager and to move its initialization into the initialize method(). This allows the InstanceManager to register and create the default and then initialize it.

[rhwood]

@bobjacobsen Does this look like an acceptable fix to #3999?

[bobjacobsen]

This looks good, both from a code point reading and from running it with my updated #3963 that starts PanelPro with a profile that currently hangs.

I think it's ready to be merged.

One question: If we have multiple sets (old and new) present, do we really want to create both in memory? Or should the older one be ignored and not loaded? Or am I misunderstanding what's happening here?

[rhwood]

One question: If we have multiple sets (old and new) present, do we really want to create both in memory? Or should the older one be ignored and not loaded? Or am I misunderstanding what's happening here?

Assuming a "set" is stored user preferences, the logic is:

• If newer set exists, use it, ignoring any possible older set.
• If newer set does not exist, but older set does, read older set to populate newer set.
• If neither set exists, create a new set and use it.
  It is entirely possible that the middle path creates, uses, and unnecessarily retains objects in memory during that one session, but I don't think it does (I have not done a memory analysis on this).

Or am I misunderstanding the question?

[bobjacobsen]

Or am I misunderstanding the question?

No, that was a nice answer, quite on point.

In some deep way, I don't have an understanding of how the preference system works within the profile-tree system. I had gone looking for some indication of how those interacted without success. Your description above is certainly a good way to handle it, I just couldn't see that's what it was doing.