[imp] remember expanded folders

[Chuck Hagenbuch]

Quoting Jan Schneider <jan@horde.org>:

> 1) Size
> We only store the names of the folders that are expanded. Most of the folders
> are leafes of the folder tree, only some are branches, t.i. expandable. And
> probably not all branches are expanded if you really have a large tree.
> We already have the nav_poll preference that stores folder names, so why
> should an expanded folders preference not work accordingly.

Maybe. Read through the IMP_Tree class some; we get a lot of information from 
the level of hierarchy _below_ what is being displayed (i.e., currently 
expanded).

> 2) Other clients
> We just check if the folder is in the stored preference while building the 
> tree. That should prevent us from problems if a folder is removed in the 
> meantime. This is something we also do with nav_poll.

And folders that are added?

-chuck

--
Charles Hagenbuch, <chuck@horde.org>
"What was and what may be lie, like children whose faces we cannot see, in 
the arms of silence. All we ever have is here, now." - Ursula K. Le Guin