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Re: `vertical-motion', `goto-line' set point to invisible text
From: |
Dmitry Kurochkin |
Subject: |
Re: `vertical-motion', `goto-line' set point to invisible text |
Date: |
Sun, 03 Jul 2011 11:31:23 +0400 |
User-agent: |
Notmuch/0.5-321-g41686e2 (http://notmuchmail.org) Emacs/23.3.1 (x86_64-pc-linux-gnu) |
Hi Eli.
On Sun, 03 Jul 2011 02:55:31 -0400, Eli Zaretskii <address@hidden> wrote:
> > From: Dmitry Kurochkin <address@hidden>
> > 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
- `vertical-motion', `goto-line' set point to invisible text, Dmitry Kurochkin, 2011/07/03
- Re: `vertical-motion', `goto-line' set point to invisible text, Stefan Monnier, 2011/07/03
- Re: `vertical-motion', `goto-line' set point to invisible text, Eli Zaretskii, 2011/07/03
- Re: `vertical-motion', `goto-line' set point to invisible text, Stefan Monnier, 2011/07/04
- Re: `vertical-motion', `goto-line' set point to invisible text, Eli Zaretskii, 2011/07/04
- Re: `vertical-motion', `goto-line' set point to invisible text, Stefan Monnier, 2011/07/04
- Re: `vertical-motion', `goto-line' set point to invisible text, Eli Zaretskii, 2011/07/04
- Re: `vertical-motion', `goto-line' set point to invisible text, Eli Zaretskii, 2011/07/04
- Re: `vertical-motion', `goto-line' set point to invisible text, Dmitry Kurochkin, 2011/07/04