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From: Eli Zaretskii <eliz@gnu.org>
Newsgroups: gmane.emacs.devel
Subject: Re: prettify-symbols-mode, derived modes, and compose-region
Date: Fri, 05 Mar 2021 17:20:46 +0200
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To: Stefan Monnier <monnier@iro.umontreal.ca>
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In-Reply-To: <jwvk0qlhbxt.fsf-monnier+emacs@gnu.org> (message from Stefan
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> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: d.williams@posteo.net,  emacs-devel@gnu.org
> Date: Fri, 05 Mar 2021 10:14:50 -0500
> 
> > If the width of the additional space is known, there's also the :width
> > display property.
> 
> Indeed, there's `:width` but in the case under discussion the desired
> with of the space is something like `1 - width-of-previous-char`, IOW
> something ELisp can't know when it puts the text property.

Yes, it can: shr.el uses these capabilities.

> I think it would take something like a `width` property that is
> non-replacing (i.e. can be applied to non-spaces and doesn't hide the
> text to which it's applied).

Yes, that's what I had in mind in my other message.