GNU bug report logs - #33664
26.1; Document vars and functions in `cursor-sensor.el'

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Package: emacs;

Reported by: Drew Adams <drew.adams <at> oracle.com>

Date: Fri, 7 Dec 2018 15:16:02 UTC

Severity: wishlist

Found in version 26.1

Done: Lars Ingebrigtsen <larsi <at> gnus.org>

Bug is archived. No further changes may be made.

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Message #44 received at 33664 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> IRO.UMontreal.CA>
To: Drew Adams <drew.adams <at> oracle.com>
Cc: 33664 <at> debbugs.gnu.org, Eli Zaretskii <eliz <at> gnu.org>
Subject: Re: bug#33664: 26.1; Document vars and functions in `cursor-sensor.el'
Date: Sun, 09 Dec 2018 14:35:42 -0500

> Specifically, I'd like to know some behavior
> differences - examples of when `intangible' text

With `intangible` you can have a situation where a chunk of code does

    (goto-char POS)
    BLAH
    BLAH
    BLAH

and it misbehaves because BLAH BLAH BLAH expects to run with point at POS,
but some other package added an `intangible` property so the goto-char
actually ended up putting point somewhere else.

IOW `intangible` breaks all kinds of invariants like

    (point) == (progn (forward-char N) (forward-char -N) (point))
    (+ N (point)) == (progn (forward-char N) (point))

[ Admittedly these invariants aren't true when you bump into EOB but
  a lot of code is prepared to deal with odd cases at EOB but is not
  prepared for such surprises happening virtually anywhere.  ]


        Stefan
This bug report was last modified 5 years and 224 days ago.

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