From: Stephen Berman <stephen.berman@gmx.net>
To: Stefan Monnier <monnier@IRO.UMontreal.CA>
Cc: 13648@debbugs.gnu.org
Subject: bug#13648: 24.3.50; remove-overlays bugs
Date: Thu, 07 Feb 2013 20:16:07 +0100 [thread overview]
Message-ID: <87y5f09bpk.fsf@rosalinde.fritz.box> (raw)
In-Reply-To: <jwvhalocckh.fsf-monnier+emacs@gnu.org> (Stefan Monnier's message of "Thu, 07 Feb 2013 11:42:46 -0500")
On Thu, 07 Feb 2013 11:42:46 -0500 Stefan Monnier <monnier@IRO.UMontreal.CA> wrote:
>> The reason for the first problem is that remove-overlays tests the
>> overlay value with eq, which fails for all strings [...]
>
> No, it won't fail on all strings. You just need to pass it the same
> string you added to the overlay, rather than a copy of it.
> I.e. this is not a bug.
Damn, I get tripped up by that a lot. And the fact that the empty
string is an exception doesn't help to keep the difference in mind.
Still, it is rather cumbersome to include appropriate let-bindings or
calls to overlay-get for each string value in each use of
remove-overlays, as opposed to adding a single equal-check to that.
>> invocation of remove-overlays is legitimate), the logic of the code is
>> that the NAME and VAL arguments are either both nil or both non-nil,
>
> Indeed.
>
>> which conflicts with the semantics of the &optional keyword.
>
> Right. We should document it in the docstring.
>
>> This means that the last call of remove-overlays in the above sexp
>> would clear any after-string overlays, regardless of their value.
>
> Normally we don't distinguish "an property FOO of value nil" and "no
> property FOO". So I think what would make sense is to say that if VAL
> is nil, then we remove any overlay whose NAME property is non-nil
> (i.e. the exact inverse from what we currently do).
>
> This said, the reason why I have not implemented this case of NAME being
> specified while VAL is left unspecified is because I haven't come up
> with a need for it. So I'd be interested to hear the backstory of
> why/where you need it.
To be honest, I'm not sure I do need it. I have code that inserts
before-string overlays with different values, some fixed and some
dynamically generated, and when these overlays need to be cleared, it
would be easier to just refer to the before-string property. But the
way I use the overlays, it actually suffices to leave out both the
property and the value, i.e. just remove all overlays in the region. At
first I thought that's not safe enough, because there could be other
other overlays at the same locations but with different properties, but
in fact I haven't needed that yet. But I guess the main thing that
confused me was the conflict with the semantics of &optional, and since
it seems easy enough to avoid, I think it would be better than just
documenting the conflict.
Steve Berman
next prev parent reply other threads:[~2013-02-07 19:16 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-07 15:09 bug#13648: 24.3.50; remove-overlays bugs Stephen Berman
2013-02-07 16:42 ` Stefan Monnier
2013-02-07 19:16 ` Stephen Berman [this message]
2013-02-08 1:45 ` Stefan Monnier
2013-02-08 14:50 ` Stephen Berman
2020-08-25 11:44 ` Lars Ingebrigtsen
2020-08-25 13:02 ` Eli Zaretskii
2020-08-25 13:55 ` Stefan Monnier
2020-08-25 14:23 ` Lars Ingebrigtsen
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