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From: Stefan Monnier <monnier@iro.umontreal.ca>
To: emacs-devel@gnu.org
Subject: Re: Difficulties with `purecopy' discarding text properties from strings
Date: Fri, 19 May 2017 15:22:50 -0400	[thread overview]
Message-ID: <jwvo9uohczs.fsf-monnier+gmane.emacs.devel@gnu.org> (raw)
In-Reply-To: 20170519185508.GA5330@acm.fritz.box

> Presumably there are good reasons for discarding text properties when
> purecopying strings.

I don't think so.

> Or, maybe, there was just no particular reason to amend the workings
> of `purecopy' when text properties came into existence.

I think that's what happens.

But wait a minute:
> I naively constructed such a defcustom, with text properties on the
> value option strings.

How exactly did you do that?  Using #("..." ...)
or using (propertize "..." ...)?

> After some debugging, I discover that defcustom strips those text
> properties off the strings.  It does this by using `purecopy' on these
> strings (in the function `custom-declare-variable').

But AFAICT custom-declare-variable only applies purecopy to its
`default` argument which is supposed to be an expression (which
evaluates to the intended value) rather than a value.  So if you use the
(propertize "..." ...)  form, the properties should not be stripped.

Or am I missing something?


        Stefan




  parent reply	other threads:[~2017-05-19 19:22 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-05-19 18:55 Difficulties with `purecopy' discarding text properties from strings Alan Mackenzie
2017-05-19 19:11 ` Daniel Colascione
2017-05-19 20:04   ` Alan Mackenzie
2017-05-19 19:22 ` Stefan Monnier [this message]
2017-05-19 19:54   ` Alan Mackenzie
2017-05-19 21:04     ` Eli Zaretskii
2017-05-20 10:29       ` Alan Mackenzie
2017-05-20  2:58     ` Stefan Monnier
2017-05-20 10:40       ` Alan Mackenzie

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