[Rd] Plotmath on Fedora 31 broken with with pango >= 1.44 - workarounds?

[Nicolas Mailhot]

Le mardi 31 mars 2020 à 10:14 +1300, Paul Murrell a écrit :
> Hi
> 
> On 30/03/20 11:12 pm, Nicolas Mailhot wrote:
> > Le lundi 30 mars 2020 à 15:24 +1300, Paul Murrell a écrit :
> > > Hi
> > > 
> > > I have created an R branch that contains a potential fix ...
> > > 
> > > https://svn.r-project.org/R/branches/R-symfam/
> > > 
> > > This allows, for example, ...
> > > 
> > > cairo_pdf(symbolfamily="OpenSymbol")
> > > 
> > > ... to specify that the OpenSymbol family should be used as the
> > > "symbol" font (e.g., for "plotmath") in R.
> > 
> > Thanks for looking at it!
> > 
> > But, really, there is no such thing as a Symbol font on Linux
> > anymore.
> > Symbol is pre-unicode thinking. Most modern general-purpose unicode
> > fonts will include every codepoint Symbol ever shipped, and
> > fontconfig
> > will fallback gracefully when that’s not the case (unless your
> > fontconfig integration is broken).
> 
> Yep, the "symbol" font is an (outdated) R "plotmath" concept, but
> one 
> that would take a fair bit of surgery to remove.  R plotmath
> converts 
> certain R expressions (in certain contexts) to code points in the
> Adobe 
> Symbol Encoding (ASM), but for cairo-based devices, those are
> converted 
> to UTF8 code points.
> 
> > Just use the sans-serif or monospace fontconfig defaults. You don’t
> > need Symbol, or OpenSymbol, or any special font setup.
> 
> Agreed.  I got reasonable coverage from DejaVu Sans and FreeSerif. 
> There are still a number of ASM code points that are not covered
> though, 
> for example, ...
> 
> F8EB	E6	# LEFT PAREN TOP	# parenlefttp (CUS)
> F8EC	E7	# LEFT PAREN EXTENDER	# parenleftex (CUS)
> F8ED	E8	# LEFT PAREN BOTTOM	# parenleftbt (CUS)
> 
> Even OpenSymbol is missing a few (though perhaps not very common
> ones) ...

All the F8* codepoints are in the private use area. That means you
can’t rely on them existing in standard unicode fonts

You need to use correct Unicode values for things to work:
Ux239… for parenthesis, brackets

https://www.unicode.org/charts/PDF/U2300.pdf

> F8E6    BD      # VERTICAL ARROW EXTENDER       # arrowvertex (CUS)
> F8E7    BE      # HORIZONTAL ARROW EXTENDER     # arrowhorizex (CUS)

and 23AF/23D0 for arrow extensions (though arrow font support seems
messy, probably because it sees little use; it’s a pity R comes so late
to the party, those are just lines, it would have been trivial to get
them into DejaVu before the project gone dormant). GFS NeoHellenic
(Math block) seems complete but it’s not a common font family.

> F6DA    D2      # REGISTERED SIGN SERIF # registerserif (CUS)
> F6D9    D3      # COPYRIGHT SIGN SERIF  # copyrightserif (CUS)
> F6DB    D4      # TRADE MARK SIGN SERIF # trademarkserif (CUS)
> F8E8    E2      # REGISTERED SIGN SANS SERIF    # registersans (CUS)
> F8E9    E3      # COPYRIGHT SIGN SANS SERIF     # copyrightsans (CUS)
> F8EA    E4      # TRADE MARK SIGN SANS SERIF    # trademarksans (CUS)

Those are useless nowadays, just use normal
registered/copyright/trademark codepoints, and a font in the wished
style (serif sans serif, whatever looks nice to you)

Regards

-- 
Nicolas Mailhot