bug#67810: 29.1; fonts use synthetic bold on Linux / pgtk

[Po Lu via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Po Lu <luangruo@yahoo.com>
>> Cc: Stefan Kangas <stefankangas@gmail.com>,  Eli Zaretskii <eliz@gnu.org>,
>>   67810@debbugs.gnu.org
>> Date: Fri, 12 Jan 2024 09:46:21 +0800
>> 
>> Tim Ruffing <crypto@timruffing.de> writes:
>> 
>> > @Po Lu:
>> > Independent of icons, I still think that overstriking is a bit
>> > unexpected. (I mean, even Eli didn't know about it.) I see that a font
>> > regex is too much, but do you think a simple boolean option would be a
>> > good idea? Or do you think the current behavior should simply be
>> > documented more prominently?
>> 
>> I think this is a mechanism users should not understand in this much
>> technical detail, because font backends might synthesize their bold or
>> oblique variants by other means when one is requested from a font that
>> doesn't provide them.  Rather, users should understand that Emacs will
>> seek to display bold text when they specify it should, and that text
>> which isn't meant to be bold text should not receive text properties
>> labeling it as such.
>
> Would it make sense to introduce a variable that disables synthesizing
> bold or oblique font variants?

I think it won't until someone informs us of how those features might be
disabled in the font drivers that perform this.  The Mac driver is
definitely one of them, and possibly the Fontconfig driver as well.