Re: High-res Customize icons

[Eli Zaretskii]

> From: Richard Stallman <address@hidden>
> Cc: address@hidden, address@hidden, address@hidden,
>       address@hidden, address@hidden, address@hidden,
>       address@hidden
> Date: Fri, 24 Apr 2020 23:30:53 -0400
> 
>   > That's not exactly why I asked whether it's a good idea.  I'm asking
>   > whether it's a good idea to use characters as if they were small
>   > images.
> 
> Could you state the issue more clearly?

I think I did, in several messages posted since the one to which you
are responding.  I prefer to wait for you to read them, before we
continue this line of discussion, because I think I already explained
everything in those followup messages, and have nothing to add to that
on this general level.

>            That is not what fonts were designed for,
> 
> If lots of programs use fonts for that job, I think we can
> conclude their design is suitable for it.

I asked whether other programs do that, and if that is considered a
good idea.  The only reply I got seemed to suggest this is not
something program usually do or consider a good idea.  Which is what
I'd expect.

>                                                      and that is
>   > definitely not what font-selection code in Emacs was designed for.
> 
> That could be an important issue.  I think it would depend on
> just where Emacs would display the images, and for what purpose.

As I said elsewhere, Emacs doesn't have such distinction.  Wherever a
character with a certain codepoint is needed, Emacs looks for a font
that can display that character.

> If they would appear within lines of text, I think it would not be
> hard to change Emacs to display them more or less as if they were
> characters.  That doesn't mean they have to be like characters at the
> level of strings or buffers.
> 
> However, if they are not like characters at that level, we would
> need to design some other Lisp-level spec for them.

AFAIU, they are indeed "not like characters".

>   > > To conform to the standard, glyphs that are not in Unicode would be
>   > > put into the PUA (Private User Area), again ensuring that there are no
>   > > conflicts with other applications.
> 
> At what levels in the code of Emacs would it be necessary to use the PUA?

I don't think I understand the question.  What are the "levels" to
consider in this context?

> Would this be limited to communication with other components of the
> operating system, such as Xlib or GTK?  If so, I think it would not
> be a problem for Emacs to do this, if it is commonplace for other
> programs to do this.
> 
> Or would this have to extend up into other levels of Emacs?

Again, I don't understand well what you mean by "levels" in this
context, but in a nutshell we will have to use these codepoints
everywhere where we use characters.

>   > I'm very much against using PUA codepoints for this purpose (or any
>   > purpose, really) in Emacs.
> 
> Could you explain?

Which part?