From: Dmitry Kurochkin <dmitry.kurochkin@gmail.com>
To: Eli Zaretskii <eliz@gnu.org>
Cc: emacs-devel@gnu.org
Subject: Re: `vertical-motion', `goto-line' set point to invisible text
Date: Sun, 03 Jul 2011 11:31:23 +0400 [thread overview]
Message-ID: <87liwf4y7o.fsf@gmail.com> (raw)
In-Reply-To: <E1QdGaZ-0003T2-4z@fencepost.gnu.org>
Hi Eli.
On Sun, 03 Jul 2011 02:55:31 -0400, Eli Zaretskii <eliz@gnu.org> wrote:
> > From: Dmitry Kurochkin <dmitry.kurochkin@gmail.com>
> > Date: Sun, 03 Jul 2011 06:59:49 +0400
> >
> > While working on notmuch [1] emacs client, I stumbled upon an unexpected
> > behavior: `beginning-of-visual-line' places point to invisible text in
> > the beginning to the line. I.e. you have:
> >
> > line1
> > line2 <--- this line is not visible
> > line3 <--- point is on this line
> >
> > in this case, `beginning-of-visual-line' will set the position to start
> > of line2 (which is invisible), not line3. It differs from what
> > `move-beginning-of-line' and even does not match
> > `line-beginning-position'. `beginning-of-visual-line' uses
> > `vertical-motion' to do the job. `goto-line' has a similar behavior. I
> > believe there are more functions like this.
>
> See the node "Invisible Text" in the ELisp manual. Some functions are
> explicitly programmed to special behavior in the vicinity of invisible
> text, others aren't.
>
Thanks for the hint.
> > This does not look right to me. I expect these functions never set
> > point inside invisible text and there should be some general way to
> > protect from this.
>
> Are you sure you don't mix invisible with intangible?
Yes, I know invisible is not the same as intangible.
> Invisible means
> just that: not shown on the screen. It doesn't mean point cannot
> enter the invisible portion. Emacs does try to move point out of
> invisible range of text, but it does so in its command loop, _after_
> the cursor motion functions and the display engine did their job.
I guess that explains why in notmuch (which has multiple lines hidden,
i.e. email body) I hit C-a, then M-: "(point)" I get X, then if I do M-:
"(point)" again, I get Y. Is there a way to ask Emacs to sync point to
visible position, so that I do not have to do it by hand?
> So
> your test program just shows that cursor motion has no problem getting
> into the invisible region, which I think is not a bug.
>
> > But perhaps I am wrong and we have to manually skip
> > all invisible text forward after any point move?
>
> Yes.
>
Thanks for your answers.
> There is something strange in how we behave in this example, though.
> To see it, modify your test program to make each line's 1st character
> different from other lines. Then, after the program ends, C-a on the
> 3rd line and type "C-x =": Emacs says the character at point is the
> first character of the invisible line 2, which seems wrong, as the
> display shows line 3. In fact, you cannot place point on the 1st
> character of line 3: C-b from the 2nd character of line 3 gets you to
> the 1st character of line 2! I think this happens because the range
> of invisible characters includes the newline of line 2.
Indeed, I did not notice that when testing in notmuch (I guess because
there are many lines hidden).
`backward-char' steps 1 position as expected. I.e. M-: (progn
(backward-char) (point)) works fine. But after that M-: (point) returns
another position which corresponds to the beginning of the hidden line.
I guess this has to do command loop I know nothing about. IMO Emacs
should not touch the point in this case, because it is already visible.
Sounds like a bug to me.
Regards,
Dmitry
next prev parent reply other threads:[~2011-07-03 7:31 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-07-03 2:59 `vertical-motion', `goto-line' set point to invisible text Dmitry Kurochkin
2011-07-03 6:55 ` Eli Zaretskii
2011-07-03 7:31 ` Dmitry Kurochkin [this message]
2011-07-03 13:33 ` Eli Zaretskii
2011-07-04 2:08 ` Dmitry Kurochkin
2011-07-03 14:50 ` Stefan Monnier
2011-07-03 15:14 ` Eli Zaretskii
2011-07-04 14:01 ` Stefan Monnier
2011-07-04 15:14 ` Eli Zaretskii
2011-07-04 18:10 ` Stefan Monnier
2011-07-04 20:06 ` Eli Zaretskii
2011-07-04 20:06 ` Eli Zaretskii
2011-07-05 2:22 ` Dmitry Kurochkin
2011-07-05 2:55 ` Eli Zaretskii
2011-07-05 3:52 ` Dmitry Kurochkin
2011-07-05 7:56 ` Eli Zaretskii
2011-07-09 13:13 ` Dmitry Kurochkin
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