Re: High-res Customize icons

[Eli Zaretskii <eliz@gnu.org>]

> Date: Thu, 23 Apr 2020 07:14:48 +0000
> From: ndame <ndame@protonmail.com>
> 
> > It should be straightforward to take a free font family, strip all
> > other glyphs, and modify the remaining symbols to make them fit.
> 
> Actually, there is an emacs package already which collects fonts
> with free license to provide icons:
> 
> https://github.com/domtronn/all-the-icons.el
> 
> Check out the screenshot, e.g. the mode line at the bottom which looks quite nice:
> 
> https://raw.githubusercontent.com/domtronn/all-the-icons.el/master/logo.png
> 
> It would be nice if emacs shipped with these fonts and actually used the icons at various
> places like on the screenshot.

Sorry, I cannot say I like this.  AFAIU, it uses Private Use Area
(PUA) codepoints to produce the icons with a specially-prepared font.
But the fonts it provides declare support for portions of Unicode
where they have glyphs for only one or a small number of characters.
So if this font is installed and available to the Emacs font-selection
routines, it will at best make the search for a font slower, and at
worst might cause some characters be displayed as boxes with hex
codes, although some other font on the system could have displayed
that character.

I'm especially alarmed to see advice like this:

  . If you don't see the font family in question in the list of
    fontspecs (i.e. [-*-file-icons-...]) below the range, or some
    other fontspecs in front of the one in question, you will have to
    add the families back to the fontset (scroll to the top to see
    which one is in effect), or arrange the fontspec order. For
    example:

     (set-fontset-font t 'unicode (font-spec :family "all-the-icons") nil 'append)

This in effect tells Emacs that the font in question covers the entire
Unicode code-space, which is definitely far from the truth.

From my POV, this has trouble written all over it.  We have enough
font-related issues reported on the bug tracker, and zero people who
know this area of Emacs well enough to respond to those bugs
efficiently.  Using tricks like the above will make a difficult
situation much more so, and for no good reason.