bug#22520: 25.0.50; unhighlight-regexp shows the scary guts of char-folding to the user

[Juri Linkov <juri@linkov.net>]

tags 22520 fixed
close 22520 28.0.50
thanks

Fortunately, both points are now implemented in bug#40337.

>> 1. Create a file t.el containing a single line
>> (message "\nDatabase directory: ")
>>
>> 2. emacs -Q t.el
>>
>> 3. C-s m (to isearch for "m")
>>
>> 4. M-s h r enter (to highlight "m" with the default face)
>>
>> 5. M-s h u
>>
>> Step 5 should offer to unhighlight "m", but it offers garbage-looking
>> text instead. Upon closer inspection, it looks like the crazy garbage is
>> actually the regexp that char-folding produces when you look for "m". I
>> don't think this is what the user should see. As one consequence of
>> this, trying to unhighlight simply "m" doesn't work, even though that's
>> what the user asked to highlight in the first place.
>
> Unlike bug#21180, it's much harder to conceal the innards of hi-lock.
> Its regexps will keep pouring in from all places.
>
>> Another possible side effect of this is that highlighting
>>
>>   Database directory:
>>
>> doesn't work: hi-lock goes through the motions but nothing ends up being
>> highlighted. Turning off char-folding fixes that.
>
> Actually “Database directory:” is not highlighted due to case-folding.
> After toggling case-folding with ‘M-s c’ and preserving the capital D,
> it's highlighted correctly.