How to remove a property from an overlay?

How to remove a property from an overlay?

[Marcin Borkowski]

Hi all,

is there any way I can remove property `prop' from overlay `ovl' besides

(overlay-put ovl 'prop nil)

which does not really remove it, only sets it to nil?

TIA,

-- 
Marcin Borkowski
http://mbork.pl

Re: How to remove a property from an overlay?

[Eli Zaretskii]

> From: Marcin Borkowski <mbork@mbork.pl>
> Date: Fri, 30 Jul 2021 20:31:35 +0200
> 
> is there any way I can remove property `prop' from overlay `ovl' besides
> 
> (overlay-put ovl 'prop nil)
> 
> which does not really remove it, only sets it to nil?

What's the difference?

Re: How to remove a property from an overlay?

[Marcin Borkowski]

On 2021-07-30, at 20:48, Eli Zaretskii <eliz@gnu.org> wrote:

>> From: Marcin Borkowski <mbork@mbork.pl>
>> Date: Fri, 30 Jul 2021 20:31:35 +0200
>> 
>> is there any way I can remove property `prop' from overlay `ovl' besides
>> 
>> (overlay-put ovl 'prop nil)
>> 
>> which does not really remove it, only sets it to nil?
>
> What's the difference?

When I say `(overlay-properties ovl)', I can see `prop' set to nil.
Before setting it, I couldn't.

-- 
Marcin Borkowski
http://mbork.pl

Re: How to remove a property from an overlay?

[Eli Zaretskii]

> From: Marcin Borkowski <mbork@mbork.pl>
> Cc: help-gnu-emacs@gnu.org
> Date: Fri, 30 Jul 2021 21:12:26 +0200
> 
> >> (overlay-put ovl 'prop nil)
> >> 
> >> which does not really remove it, only sets it to nil?
> >
> > What's the difference?
> 
> When I say `(overlay-properties ovl)', I can see `prop' set to nil.
> Before setting it, I couldn't.

And why is that difference important?

Overlay properties exist to search for them with the likes of
next-single-char-property-change, and those don't distinguish between
the two.

But if you must remove the property, I think the only way is to make
another overlay with all the properties except the one you want to
remove.

Re: How to remove a property from an overlay?

[Stefan Monnier via Users list for the GNU Emacs text editor]

Marcin Borkowski [2021-07-30 20:31:35] wrote:
> is there any way I can remove property `prop' from overlay `ovl' besides
> (overlay-put ovl 'prop nil)
> which does not really remove it, only sets it to nil?

The recommendation is to try and make sure you always give semantics to
those properties such that nil behaves the same as the absence of
the property.


        Stefan

Re: How to remove a property from an overlay?

[Marcin Borkowski]

On 2021-07-30, at 21:47, Eli Zaretskii <eliz@gnu.org> wrote:

>> From: Marcin Borkowski <mbork@mbork.pl>
>> Cc: help-gnu-emacs@gnu.org
>> Date: Fri, 30 Jul 2021 21:12:26 +0200
>> 
>> >> (overlay-put ovl 'prop nil)
>> >> 
>> >> which does not really remove it, only sets it to nil?
>> >
>> > What's the difference?
>> 
>> When I say `(overlay-properties ovl)', I can see `prop' set to nil.
>> Before setting it, I couldn't.
>
> And why is that difference important?

Because of my OCD, perhaps?

> Overlay properties exist to search for them with the likes of
> next-single-char-property-change, and those don't distinguish between
> the two.

I see.

> But if you must remove the property, I think the only way is to make
> another overlay with all the properties except the one you want to
> remove.

I see.  Not worth it, of course.

Thanks!

-- 
Marcin Borkowski
http://mbork.pl

Re: How to remove a property from an overlay?

[Marcin Borkowski]

On 2021-07-30, at 22:02, Stefan Monnier via Users list for the GNU Emacs text editor <help-gnu-emacs@gnu.org> wrote:

> Marcin Borkowski [2021-07-30 20:31:35] wrote:
>> is there any way I can remove property `prop' from overlay `ovl' besides
>> (overlay-put ovl 'prop nil)
>> which does not really remove it, only sets it to nil?
>
> The recommendation is to try and make sure you always give semantics to
> those properties such that nil behaves the same as the absence of
> the property.

Could that be put in the manual?

-- 
Marcin Borkowski
http://mbork.pl

Re: How to remove a property from an overlay?

[Fu Yuan]

> 在 2021年7月31日，上午4:46，Marcin Borkowski <mbork@mbork.pl> 写道：
> 
> 
>> On 2021-07-30, at 22:02, Stefan Monnier via Users list for the GNU Emacs text editor <help-gnu-emacs@gnu.org> wrote:
>> 
>> Marcin Borkowski [2021-07-30 20:31:35] wrote:
>>> is there any way I can remove property `prop' from overlay `ovl' besides
>>> (overlay-put ovl 'prop nil)
>>> which does not really remove it, only sets it to nil?
>> 
>> The recommendation is to try and make sure you always give semantics to
>> those properties such that nil behaves the same as the absence of
>> the property.
> 
> Could that be put in the manual?

Reminds me of the similar property of plists, we could also add to plist’s manual.

Yuan