bug#27122: 26.0.50; [PATCH] Add customizable to display unprintables as hex

[Eli Zaretskii]

> From: Robert Cochran <robert+Emacs@cochranmail.com>
> Cc: Eli Zaretskii <eliz@gnu.org>,  27122@debbugs.gnu.org
> Date: Mon, 29 May 2017 11:46:03 -0700
> 
> what is wrong with adding what is clearly an option, so it can be
> changed in one place and be done with it?

Complexity and maintainability.  The code which handles special
characters is already almost 140 lines of terse C, controlled by 2
obscure variables (ever heard of printable-chars, for example?) and 2
special faces.  And that's excluding the glyphless-char-display stuff,
which adds even more.  It's almost impossible to tell in advance how
will some specific codepoint be displayed if the terminal cannot
handle it "normally".  At least I need to read the involved code every
time I have to answer such questions.

I'd rather not add to this any more complexity, unless it's really
needed.  That is why I'd like to understand the details of the use
case: to see whether we already have a reasonable solution for it.