bug#58168: string-lessp glitches and inconsistencies

[Mattias Engdegård]

1 okt. 2022 kl. 12.02 skrev Lars Ingebrigtsen <larsi@gnus.org>:

> Funnily enough, the latter displays in a different way for me, which may
> or may not be a bug:
> 
> This is with `display-raw-bytes-as-hex' t.

You are right, that is completely broken -- display-raw-bytes-as-hex shouldn't 
affect the display of C1 controls.
Whether (string 128) displays "\200" or "\x80", however tarted up in a fancy 
face, it's still a lie. Only something like "\u0080" would actually be correct.

It seems to be a relic from the pre-Unicode days of Emacs: the code responsible 
muddles the display of raw bytes and unicode controls.
The attached patch untangles the two somewhat and lets display-raw-bytes-as-hex 
do what its name and documentation suggest, while using a non-confusing display 
for C1 controls.

The command

  (insert "C1: " (string 128) " raw: " (unibyte-string 128) ".\n")

currently displays

   C1: \200 raw: \200.
or
   C1: \x80 raw: \x80.

depending on display-raw-bytes-as-hex. With the patch, we get

€ €  €C1: \u0080 raw: \200.
or
   C1: \u0080 raw: \x80.

which should satisfy everyone. What about it?

unicode-escape-display.diff
Description: Binary data

I see that the redisplay-testsuite.el needs amending too; it actually looks 
buggy in this respect. If the above approach is deemed acceptable, I'll submit 
a patch that includes that file as well.