[sugar] Implicit saving

[Eben Eliason]

> The implicit saving on activity close gets in the way of how etoys
> traditionally worked. If I create, say, a simulation, I will arrange
> everything and then save that project, so when I later open it for
> demonstration, it is in a state ready to be started. But when I then
> run the simulation and quit, it will not be in the ready-to-run state
> anymore.
>
> Any idea how that problem should be tackled in Sugar?

Hmmm, that's a little tricky.  The implicit saving is designed to
track versions naturally and to prevent data loss, but it does seem to
get in the way in this case. I don't know the APIs myself, but I
assume the activity gets prompted to save upon close and then handles
the save itself.  It seems you could keep track of "read" vs "write"
actions, where pressing "run" or "reset" buttons (basically a revert
button) wouldn't count as "write" modifications.  You would only need
to save upon close if code or graphics were actually changed during
the session.

In any case, you might actually think of this to your advantage.
Since the files are (will be) properly versioned, this implicit save
hasn't actually erased your default simulation setup, which will still
live in the Journal as an entry from yesterday when you set it all up.
 Instead, you now have that "starting state" entry and one or more
"experiment" entries which represent the results of running that
simulation.  With randomness this could actually create a series of
interesting results that would be useful for learning.

- Eben