Re: On the masking of undisplayable characters

[Juri Linkov]

>> Emacs always
>> displayed special characters specially.  Think about the ^X control
>> characters,
>
> That's fine. When I see a blue ^X, I know that's a control character, it's
> very clear that it's not a ^ with an X.

Highlighted using the ‘escape-glyph’ face.

>> the glyphless-char-display feature,

The ‘glyphless-char’ face.

>> composed characters,
>
> You mean like a non-spacing ` and a looking like an à? The non-spacing
> characters are specifically designed to do that, it's not the same as
> displaying one quote as another quote.

Another face intended to highlight confusable characters is ‘nobreak-space’.
But note how ‘gnus-article-mode’ uses

  (set (make-local-variable 'nobreak-char-display) nil)

to prevent Gnus from displaying non-break space with `nobreak-space' face
because usually in view modes users don't want displaying special characters
specially.

>> even the newline.
>
> You mean that \n and \r\n are displayed the same way? Yeah, I've been bit
> several times by it, but at least it's indicated in the mode line.

I've been bit more by indicating different codings in the mode line
with the same code letter, e.g. using the same letter ‘U’ for
utf-8, utf-16le, utf-16be, etc.  Better would be to display coding systems
as full names but this makes the mode line wider.