bug#18077: 24.4.50; Info-quoted face should inherit default

[Sebastian Wiesner <swiesner@lunaryorn.com>]

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Am Freitag, 25. Juli 2014, 15:11:42 schrieb Eli Zaretskii:
> > From: Sebastian Wiesner <swiesner@lunaryorn.com>
> > Cc: 18077@debbugs.gnu.org
> > Date: Fri, 25 Jul 2014 12:25:47 +0200
> > 
> > > Would you like to suggest a patch for fixing this problem?  Please
> > > note that the underlying issue here is that the font should provide
> > > nice-looking glyphs for the Unicode quote characters.
> > 
> > I do not think that I am in a position to suggest a patch that could
> > generally fix this problem.  I use Emacs only in two different
> > environments, and have no idea of what limits and constraints Emacs must
> > obey with regards to fonts to remain portable across various platforms.
> > 
> > I can only say that for my case it would be entirely sufficient to simply
> > make Info-quoted inherit from default, i.e. use '((:inherit default)) as
> > spec in defface.
> > 
> > But I only use a GUI Emacs, and only on very recent and modern systems
> > (Arch Linux with KDE, and OS X 10.9), where Unicode fonts are less of a
> > problem.  On these systems Emacs typically picks a font with good unicode
> > coverage for the default face automatically, e.g. DejaVu Sans Mono or a
> > variant thereof.
>
> Character coverage is not the problem.  The problem is that some
> widely used fonts that cover these characters have ugly or barely
> visible glyphs for them.

I see.  I doubt, though, that "courier" has generally better quote glyphs than 
those  decent modern fonts that are typically used for the default face, 
either automatically or by user customization.

Take a look at the attached images, which show the quote characters of various 
fonts in Emacs on both of my systems:  

On OS X, the quote characters of Courier aren't any better than that of the 
standard monospace faces Menlo and Monaco.  On Linux, Courier isn't even anti-
aliased.  And in both cases the quote characters of Courier are worse than 
those of Source Code Pro and Inconsolata, which are popular 3rd party fonts.

Now, I understand that my setup is just some example and by no means 
authoritative, and that Courier may look significantly different and much 
better on your Linux system.

But I'm trying to demonstrate with these examples that Courier is by no means 
*guaranteed* to have good quote characters, and can in fact be significantly 
worse than other fonts.  

IOW, there's a chance that Courier gets it right, and there's also a good 
chance that Courier gets it wrong.  And that goes for the default face as 
well:  It can either have good quotes, or bad ones. 

However, the default fonts of modern systems are typically not that bad, and 
users typically don't choose very poor fonts for their "default" face, so I 
think it's less likely for "default" to get it wrong that for "Info-quoted".  
And the latter can fail really bad, as seen in my Arch Linux example.

 
> > inheriting from default seems to be the standard among other
> > built-in faces.
> 
> I would trust Stefan (who introduced this face) that he knows that for
> quite some time, and had his reasons for not doing that.

I'd trust Stefan to the end of the universe, for sure, but he might just have 
been lucky to have a proper Courier variant installed on his own systems.  
Even he can't test a face on each and every font setup out there :)

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