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

[Vasilij Schneidermann <v.schneidermann@gmail.com>]

> 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.

While this is unfortunate, I find it more instructive to look at it in
terms of how much complexity is added (an extra conditional and a
customizable), not how much lurks in the existing code.  If you
constantly went by that argument, you would have to refrain from any
kind of Emacs hacking given its impenetrable code base.

The easiest way to solve this without adding any extra complexity would
be simply replacing the format string by the hex one.  I wouldn't want
to be involved in the ensuing discussion though...