bug#57113: 29.0.50; Confusing icon customization interface

[Po Lu via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Lars Ingebrigtsen <larsi@gnus.org> writes:

> See icons.el.

That doesn't help, since I want to change an existing icon, not
introduce a new one.

> You've probably never seen another system that had just introduced a new
> language level mechanism for icons a couple weeks earlier, either?

Language-level mechanism?

> Like I said, fixing Customize to be less awful would be very welcome.

It's not a problem with Customize.  Customize is for customizing faces
and variables.  `customize-icon' is something new, so the problem is
there.

> Please go ahead.

I'm afraid I don't understand how icons.el is supposed to work, and it
seems overcomplicated.

How about replacing it with something straightforward, such as a single
function insert-icon, which inserts the appropriate icon according to a
list of image specs?  Then, the first image in the list that can be
displayed is inserted into the buffer.

Fallback text can also be supplied as the last element of the list, and
is displayed on terminals that do not support images.