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Date: Wed, 19 Mar 1997 12:29:28 -0500 (EST)
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From: Kyle Jones <kyle_jones@wonderworks.com>
To: XEmacs Beta Mailing List <xemacs-beta@xemacs.org>
Subject: RFC undo changes
In-Reply-To: <199703191545.AAA00194@Pentagana.sonic.jp>
References: <199703191545.AAA00194@Pentagana.sonic.jp>
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P E Jareth Hein writes:
 > While working on input systems, I've come across a need/desire to add
 > to the classes of things that can be in buffer-undo-list. I'd like to
 > propose adding a way to put a function on the list, so that when hit
 > it could put several things like translation states, etc back in one
 > foop. Of course, I'm proposing to do most of the work (although I'm
 > not adverse to help... ;-) ) but I was wondering if anyone would get
 > all fired up screaming upset at this, which is probably yet another
 > way XEmacs will diverge from FSFmacs.

When I last looked at the undo code (recently), it was not safe
to run Lisp code in Fprimitive_undo.  What is done instead is to
encode actions in some way that Fprimitive_undo understands and
Fprimitive_undo calls internal functions to perform the undo
action.

I would only get screaming upset if the things placed on the undo
list are unrelated to buffer modification.

