bug#35797: 26.2; Adaptive Wrap does not respect Whitespace Mode faces

[Andrew T]

> So, AFAIU, your problem is that you don't like whitespace-mode
> displaying the whitespace in the wrap-prefix as "normal" space
> characters, i.e. as "dots", and not as whitespace in
> indentation.  And the exact face in which these "dots" are displayed
> is not the issue. Is my understanding correct?

Technically, the wrap prefix is *not* being displayed like normal space
characters. The wrap prefix gets displayed in the buffer's default
foreground and background colors, even though *none* of the configured
Whitespace faces use this these colors.

> If my understanding is correct, then whitespace.el cannot do that: it
> only recognizes indentation by looking at characters in the buffer
> that follow a newline.  By contrast, wrap-prefix doesn't come from
> the buffer, and doesn't follow a newline.  So whitespace-mode simply
> doesn't understand that the wrap-prefix is indentation of sorts.

That's a plausible theory. Adaptive Wrap doesn't actually modify the
buffer contents, so Whitespace Mode doesn't see the wrap prefix...
Except then it seems odd to me that the dots appear at all, instead of
merely using the default (wrong) colors.

Like, I would expect the opposite situation: Say, if I left the special
colors representing indentation or mid-line spaces enabled, I might
expect Whitespace Mode *not* to apply those at all to the wrap prefix,
so that they appear as regular unhighlighted spaces even if I did want
them highlighted. Yet even when testing from `emacs -Q`, where all I do
is disable long lines in Whitespace Style, the Adaptive Wrap prefix
still shows in the buffer default colors, which matches none of the
default colors in the Whitespace Mode faces.

¯\_(ツ)_/¯