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>]

Tim Ruffing <crypto@timruffing.de> writes:

> On Wed, 2023-12-13 at 15:39 +0200, Eli Zaretskii wrote:
>> 
>> Maybe this is done by the calls to the font backend with FC_EMBOLDEN
>> parameter?  I'm no expert on these font backends, but maybe you could
>> play with those calls and see if disabling them gets you what you
>> want?  You can find the relevant code by searching the C sources for
>> FC_EMBOLDEN.
>
> Thanks for the suggestion, but no luck unfortunately. What also didn't
> help is going back to Xft by configuring like this:
> ./configure --without-pgtk --without-cairo 
>
> I don't know what to try next, I guess it will be useful to have
> someone more familiar with the font stuff look at this. 

There's no bug here: when a bold face is displayed by a font which
doesn't provide a bold variant, Emacs overstrikes text displayed in that
font to create visual contrast between the bold text and its
surroundings.  This is implemented independently of font backend
features such as FC_EMBOLDEN.

If this contrast is undesirable, remove the weight attribute from the
face.