Path: utzoo!utgpu!watmath!uunet!tut.cis.ohio-state.edu!UUNET.UU.NET!mcvax!emeraude.dedlpr.bull.fr!macrakis
From: mcvax!emeraude.dedlpr.bull.fr!macrakis@UUNET.UU.NET (Stavros Macrakis)
Newsgroups: gnu.emacs.bug
Subject: Outline and undo
Message-ID: <8812281146.AA30417@emeraude.dedlpr.bull.fr>
Date: 28 Dec 88 11:46:55 GMT
Sender: daemon@tut.cis.ohio-state.edu
Distribution: gnu
Organization: GNUs Not Usenet
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GNU Emacs 18.50.3 of Wed Aug 17 1988 on rigel (usg-unix-v)

It might be nice if outline show/hide actions were undoable.
Obviously, no information is lost by these actions, so undo is not
needed to save the user from errors, however undo has another useful
property: it reassures users.  Especially for novices, knowing that
any action can be undone encourages experimentation.  (Of course,
there's always show-all in the outline case...)

In looking at the code, I noticed that undo records are always in the
form of characters saved.  If this is not considered efficient enough,
it might be useful to have the equivalent of unwind-protect, that is,
to allow an action to specify its own undo action.  Such a mechanism
could be useful in other cases where little information is lost but
many characters in the buffer are changed.

Note also that undoability and bf_modified should probably be
decoupled.