managing project changes

[garfieldnate]

I have conflicting complaints from two users:

1. If VisualSoar crashes, project changes are lost.
2. VisualSoar always saves the project (op. hierarchy + DM) on exit, and there's no undo functionality for project changes, making it difficult to back out of regretted changes. It essentially requires the user to ensure the project is backed up elsewhere (e.g. git) before opening in V-S.

1 can be alleviated with #23, though I wonder if we should also save the project file to disk after every change, rather than once every 3 minutes.

For 2, implementing undo/redo functionality would not be difficult, but I'm not sure about the UX; ctrl-z/ctrl-y are used for undo/redo in the text editors, and I don't want to confuse users by mixing project changes into the same undo stack. We could just have a menu item with a list of actions to undo/redo.

2 would also be resolved by simply asking the user if they want to save the project before doing so, but that conflicts with 1.

What I suggest we do:

• add a new preference, "auto-save project", that saves the project after changes to the DM or operator hierarchy.
• If the preference has never been set, we ask the user in a dialog box whether they want to activate it.
• If the project has been changed but not saved, indicate this with a visual marker somewhere.
• At exit time, if the project is not saved, confirm with the user before saving it.
• We should also implement Visual Soar should warn user when auto-backup file is newer than main file #23 to help with lost changes to .soar files.