bug#19889: bug#22207: emacs-25 mishandles info code text on Fedora 23

[Paul Eggert <eggert@cs.ucla.edu>]

On 05/06/2016 12:01 PM, Eli Zaretskii wrote:
> I very much doubt there are too many
> variants out there.  We could enumerate them all, and try one after
> another, or even do it specifically for each platform.  Which is more
> or less what your patch does, isn't it?

Yes, that's why I want to install the patch. :-)

>> In further testing on my Fedora 23 host I discovered another suitable 
>> anti-aliased font, Courier 10 Pitch.
> So why do you say above you don't have Courier?

Because I don't have it exactly. The font on Fedora 23 is called "Courier 10
Pitch", not "Courier". It's from Bitstream and is quite close but not identical
to honest-to-goodness IBM Courier.

I just now checked another desktop, running Ubuntu 16.04, and it has the same
set of suitable fonts as Fedora 23. (It also has a Thai font that would suffice
for ASCII but this is probably not a good choice in general.)

> We could systematically review the most popular platforms (how many
> are there, anyway?), and simply state a font or a couple of them for
> each platform.  And I won't be surprised if all of them mostly use the
> same fonts, even if some of them aren't necessarily present sometimes.
>
> IOW, I prefer naming fonts rather than asking for them via families.

The problem with Courier is that there are so many fonts that are all so similar
to Courier and most people can't tell the difference. This is partly due to the
intellectual history behind Courier.

I looked for a good source about this issue, and found someone who took a
circa-2012 census of Courier-like fonts on various web browsers and who
evaluated their looks when combined with non-Courier fonts. He writes that on
GNU/Linux platforms, the most common Courier fonts were Nimbus Mono L (98.2%)
and FreeMono (85.2%) but these fonts are a bit faint to be mixing with other
fonts, and that Courier 10 Pitch (85.0%) was a better choice. On OS X, he writes
that Courier Std (2.1%), Consolas (48.6%), and Courier (99.5%) are all good
choices, whereas Courier New (96.8%) is a bit faint. On MS-Windows, he says
Consolas (88.6%) and Courier (3.6%) are good choices, whereas FreeMono (0.6%)
and Courier New (99.8%) are a bit faint. As a result of all this, he suggests
the following order for Web use: "Courier 10 Pitch", "Courier Std", Consolas,
Courier, "TeX Gyre Cursor", TeXGyreCursor, "Nimbus Mono L", FreeMono,
"Courier New", monospace. See
<http://www.grputland.com/2012/08/font-stacks-that-look-similar-in.html#cour20120806>.

I doubt whether GNU Emacs should be defaulting to the non-free fonts in that
list(e.g., Consolas), given that the free fonts are so widely available.Courier
New is often disliked (it was digitized directly from the IBM Selectric golfball
which was at odds with how the Selectric actually worked). I don't know about
TeX Gyre Cursor, but it doesn't seem to be common on Fedora and Ubuntu anyway.
The other Courier-like fonts are close to the list I already proposed.