From: Eli Zaretskii <eliz@gnu.org>
To: Dmitry Gutov <dgutov@yandex.ru>
Cc: 18285@debbugs.gnu.org
Subject: bug#18285: 24.3.92; A combination of `display' on text and `invisible' and `before/after-string' leads to the before/after string being displayed twice
Date: Fri, 22 Aug 2014 09:41:25 +0300 [thread overview]
Message-ID: <83bnrdauwa.fsf@gnu.org> (raw)
In-Reply-To: <53F695CF.1040606@yandex.ru>
> Date: Fri, 22 Aug 2014 04:58:55 +0400
> From: Dmitry Gutov <dgutov@yandex.ru>
> CC: 18285@debbugs.gnu.org
>
> On 08/21/2014 08:06 PM, Eli Zaretskii wrote:
>
> >> If the `invisible' starts even one character earlier, it *is* the other
> >> way around.
> >
> > Yes, because then there's no doubt about the order of evaluating the
> > various properties and acting upon them. By contrast, when they all
> > begin at the same buffer position, the order is
> > implementation-defined. The code is written to examine display
> > properties before the invisible properties.
>
> Okay, but I'll take this to mean that hitting the changed behavior in
> existing code would be pretty rare.
I have no idea how rare it will be. FWIW, for the past year, all the
display-related bugs are for pretty rare cases. What does that tell
you about user expectations?
> Anyway, how about the other way around? I'll like this less, but why not
> make `invisible' inactive when `display' is set?
That's what Emacs does already. The only place where invisible still
matters in this situation is when deciding how and where to display
overlay strings. I thought I explained that earlier in this thread.
> >> Maybe. But at least it's consistent with the overlay priority rules.
> >
> > The priority is _per_buffer_position_. We tend to forget that text
> > properties and overlays in Emacs are _character_ properties, but the
> > display engine is designed and implemented to support that, and in
> > some obscure cases, like this one, it is impossible to understand its
> > logic, unless one remembers this simple fact.
>
> I'm just quoting Stefan from that discussion:
>
> """
> Same problem: for two overlays of equal `priority', the shorter one has
> higher priority, so your original example is already one of those
> cases, AFAIC.
> """
This again omits the basic fact that properties and overlays are per
character.
> (let ((pt (point)))
> (insert "aaa")
> (let ((o (make-overlay pt (point))) (v (make-overlay (1+ pt) (1-
> (point)))))
> (overlay-put o 'face 'bold)
> (overlay-put v 'face 'default)))
>
> the middle character has normal weight, even though it's also covered by
> an outer overlay that sets `face' to `bold'.
>
> So, if I had to pick which single string to show (STRING1 or STRING2),
> the latter seems to be the more consistent choice.
My opinion is that users and Lisp programmers should not enter these
dark corners.
next prev parent reply other threads:[~2014-08-22 6:41 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-17 22:35 bug#18285: 24.3.92; A combination of `display' on text and `invisible' and `before/after-string' leads to the before/after string being displayed twice Dmitry
[not found] ` <handler.18285.B.140831493931056.ack@debbugs.gnu.org>
2014-08-18 1:06 ` bug#18285: Acknowledgement (24.3.92; A combination of `display' on text and `invisible' and `before/after-string' leads to the before/after string being displayed twice) Dmitry Gutov
2014-08-18 15:07 ` bug#18285: 24.3.92; A combination of `display' on text and `invisible' and `before/after-string' leads to the before/after string being displayed twice Eli Zaretskii
2014-08-21 14:07 ` Dmitry Gutov
2014-08-21 14:57 ` Eli Zaretskii
2014-08-21 15:40 ` Dmitry Gutov
2014-08-21 16:06 ` Eli Zaretskii
2014-08-22 0:58 ` Dmitry Gutov
2014-08-22 6:41 ` Eli Zaretskii [this message]
2014-08-22 11:41 ` Dmitry Gutov
2014-08-22 13:31 ` Eli Zaretskii
2014-08-22 20:01 ` Dmitry Gutov
2014-08-22 20:55 ` Eli Zaretskii
2014-08-24 1:28 ` Dmitry Gutov
2014-08-24 2:44 ` Eli Zaretskii
2014-08-23 23:21 ` Dmitry Gutov
2014-08-24 2:40 ` Eli Zaretskii
2014-08-24 2:48 ` Dmitry Gutov
2022-04-18 11:39 ` Lars Ingebrigtsen
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