bug#9324: 24.0.50; Movement past end of screen causes weird jump

[Ivan Andrus]

On Aug 19, 2011, at 12:41 PM, Eli Zaretskii wrote:
>> From: Ivan Andrus <darthandrus@gmail.com>
>> Date: Fri, 19 Aug 2011 12:02:58 +0200
>> Cc: Antoine Levitt <antoine.levitt@gmail.com>,
>> 9324@debbugs.gnu.org
>> 
>> I just noticed something.  I use `hl-sexp-mode' from 
>> http://edward.oconnor.cx/elisp/hl-sexp.el to highlight the current sexp that 
>> I am in (or touching if at the top level).  This means when point is right 
>> after a top level sexp that sexp is highlighted.  Immediately after running 
>> the forward-sexp the defadvice sexp is highlighted.
> 
> Didn't you say that all this happens in "emacs -Q"?  Then how come
> hl-sexp happens to be loaded?

Sorry for the confusion.  Of course this doesn't happen with emacs -Q, only 
when running it with my .emacs.  I just thought it might be helpful.

>> Of course, any sort of movement changes the highlighting, but it seems to 
>> indicate that:
>> 
>> 1. it moves point correctly
>> 2. realizes that it has to recenter
>> 3. recenters the cursor but not the buffer display.
> 
> With your original recipe, and without loading hl-sexp in any way,
> what does "C-x =" say about point, after running forward-sexp?


Ah.  Well today starting from emacs -Q I can't reproduce it.  However, if I 
load my .emacs I still can't reproduce it in that same emacs.  One difference 
that I notice today is that after running the progn I can read the top line 
namely "208. ..." instead of only the continuation of that line.  I swear it 
worked yesterday, that is that I saw the bug in emacs -Q.

In case you are interested in what happens in my contaminated emacs, if I run 
C-x = after (forward-sexp) then it says a left parenthesis, but if I use 
`(progn (forward-sexp)(what-cursor-position))` then it says the next character 
is C-j.  Furthermore, changing it to (prog2 (forward-sexp) 
(what-cursor-position) (redisplay)) causes it to work properly (i.e. no bug).

I guess I'm probably on my own on this one, since even I can't reproduce it 
reliably in emacs -Q, so what functions that I should start debugging?

Thanks,
Ivan