bug#10195: 24.0.92; M-w may no longer provide visual feedback

[Michael Welsh Duggan]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Michael Welsh Duggan <md5i@md5i.com>
>> Cc: Jay Berkenbilt <ejb@ql.org>,  10195@debbugs.gnu.org
>> Date: Sat, 03 Dec 2011 00:31:36 -0500
>> 
>> >> Type some text.  Save it in the kill ring with
>> >> 
>> >> C-a C-SPC M-f M-w
>> >> 
>> >> Then do this again:
>> >> 
>> >> M-w
>> >> 
>> >> In emacs 23, the cursor would bounce between the point and the mark the
>> >> second time M-w was pressed, since the highlighting of the region turned
>> >> off after the first time.  Or, if transient-mark-mode is nil, then the
>> >> first M-w would bounce the cursor between the point and mark.  In
>> >> emacs24, M-w seems to never cause the cursor to bounce between the point
>> >> and mark.
>> >
>> > It still does that to me, in the current trunk tip.
>> >
>> > Does it work in "emacs -Q" for you?
>
> For the record, Jay replied off-list that "emacs -Q" has the same
> problem for him.
>
>> It appears to be inconsistent.  Sometimes it will happen, sometimes it
>> will not.  I first noticed this many months ago, but at the time
>> couldn't cause it to happen on command, and as such forgot about it for
>> a while.  Today, I tried again with emacs -Q built from bzr revno
>> 106562.  I definitely see this behavior, without fail.
>> 
>>   emacs -Q
>>   (In *scratch* buffer)
>>   C-p C-p C-p C-SPC C-e M-w
>
> This is not the right recipe.  The first M-w does NOT show the region
> by momentarily moving point to its other end, because the default is
> to have transient-mark-mode on, which already shows the region.  You
> need to type M-w twice or more in a row to see point move.

Sorry, I forgot to type the second M-w.  I usually use emacs without
tmm, and that is why I made that error.

> Anyway, I don't see it on any machine to which I have access, FWIW.  I
> tried both unoptimized and optimized builds, on Windows and on
> GNU/Linux, and they all behave as expected.

I just tried this again in a random buffer in my running non -Q emacs.
The first M-w caused the cursor to bounce, the second did not, the third
did, the fourth and fifth did not.  This is why I called the behavior
inconsistent.  I just tried it in emacs -Q again, and had it bounce
three times out of 15 tries.  When it does bounce, and the mark and
point are on different lines, I also see the line indicator change along
with the bounce.  When it does not bounce, the line indicator does not
change.

I am running in an unoptimized debug build with assertions turned on,
and am familiar with gdb.  If there is any way I can help debug this,
please let me know.

-- 
Michael Welsh Duggan
(md5i@md5i.com)