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Re: Advice on troubleshooting function to "unscroll"

From: Will Monroe
Subject: Re: Advice on troubleshooting function to "unscroll"
Date: Sun, 25 Jan 2015 15:43:52 -0600
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Thanks for your quick and friendly response!

On 01/25/2015 03:35 PM, Marcin Borkowski wrote:

On 2015-01-25, at 21:52, Will Monroe <> wrote:


I'm studying Emacs Lisp so that I can become more proficient at
customizing GNU Emacs for purposes, mainly using org-mode.  I'm studying
alone using Bob Glickstein's *Writing GNU Emacs Extensions*.  So far,
the book has been a terrific guide to basic concepts.  But I've run into
a problem that I can't seem to troubleshoot any further and I'd
appreciate advice on: 1) the best way to troubleshoot this problem
(e.g., other forums, listservs, or IRC channels that might be more
appropriate) and 2) troubleshooting the problem itself.  I apologize in
advance if this query has failed to take into account any basics or if
it would be better posed elsewhere.  I welcome your on the best way to

Welcome to the land of Elisp.  (I'm also a relative newcomer here.)

BTW, I looked at the free sample of Glickstein's book in the Amazon
Kindle store (not that I recommend it -- in fact, it is seemingly
prohibited to recommend things like that here), and got the impression
that it is a nice book -- something to read right after the "Emacs Lisp
Intro" by Robert J. Chassell -- but it might be a bit outdated.

Thanks for this suggestion!

instance, the early part about problems with C-h and backspace seem to
be irrelevant nowadays.)

You know, I wondered about the backspace and C-h too. But then I heard an interview RMS did on some podcast recently and he mentioned some early design differences between Emacs developers on this point. Perhaps intended as a humorous anecdote? ; )

A question to more knowledgeable people: is
that impression correct?

So, following Glickstein's advice in Chapter 3, I'm trying to create a
function that will allow me to create an "unscroll" function that will
allow me to return to a prior buffer position after (inadvertently)
pressing C-v a few times.  The code to do this defines three new
variables, defines advice for an extant Emacs function, scroll-up, and
then defines a new function, unscroll.  The code is below.

Please note that there is new syntax for advising functions in Emacs
24.4 (or 25, I'm not sure).  The old one should work, but the new one is
much simpler.

Thanks for this tip. In the first three chapters, I recall seeing a few references that were a bit dated but I just worked around them. But your mentioning this brings to mind the possibility that code provided in the book is so dated that it might explain why it fails to work as I expect. But knowing so little about lisp, It's hard to say.
"DePaul Online Teaching Series: Facilitating effective online learning

The test was just opening a lengthy file, usually an info page or an
existing org-mode file, pressing C-v a few times, and then using M-x
unscroll.  In all cases, I found that M-x unscroll would return to the
position just before the last C-v but not to the original position.  In
other words, if I pressed C-v two times and then pressed M-x unscroll,
in would only go back one C-v.  My intent, and that of the example in
the book, is to return the point the position before any C-v key
sequences were pressed.

I could move one but I suspect that the mistake I've made will come up
again.  I'd really welcome your (gentle) feedback!

I would strongly advise (no pun intended) to read the Emacs Lisp
reference, section about Edebug.

Thanks for the advice about Edebug. It's definitely something that is on my mind. But over the last day or so, I've hesitated from diving into Edebug because there was no "error" as such. That is, the code "worked" it just didn't do what I intended. Wasn't sure Edebug would help in a case like that...but your point is well taken. Thank you!

All the best,


The same to you,

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