Greek capital letters with Latin Modern and TeX

Question

Copying the plain TeX format, my formatting file contains the lines

\font\tenrm="[lmroman10-regular.otf]:mapping=tex-text"
\textfont0=\tenrm
\def\rm{\fam0 \tenrm}

to load a unicode font. However, as mentioned in Can I typeset greek letters in text mode using Latin Modern Fonts?, the Latin Modern fonts don't include the Greek capital letters, so $\Pi$ doesn't display the capital letter Pi. How can I fix this in (Xe-)TeX?

Answer 1

If you want that the Greek letters respect the current family you have to completely redefine the math fonts, probably using Latin Modern Math.

A better way to define them as “fixed” symbols is as follows:

\font\tenrm="[lmroman10-regular.otf]:mapping=tex-text"
\textfont0=\tenrm

\font\greekcapstenrm=cmr10
\font\greekcapssevenrm=cmr7
\font\greekcapsfiverm=cmr5

\newfam\greekcapsfam
\textfont\greekcapsfam=\greekcapstenrm
\scriptfont\greekcapsfam=\greekcapssevenrm
\scriptscriptfont\greekcapsfam=\greekcapsfiverm

\begingroup
\def\getlastdigitsaux#1"#2#3#4#5{#4#5}
\def\getlastdigits#1{\expandafter\getlastdigitsaux\meaning#1}
\def\redefine#1{%
  \begingroup\edef\x{\endgroup
    \global\Umathchardef#1=
    0 % math kind
    \greekcapsfam % family
    "\getlastdigits#1 % slot
  }\x
}

\redefine\Gamma
\redefine\Delta
\redefine\Theta
\redefine\Lambda
\redefine\Xi
\redefine\Pi
\redefine\Sigma
\redefine\Upsilon
\redefine\Phi
\redefine\Psi
\redefine\Omega
\endgroup

$\Gamma\Delta\Theta\Lambda\Xi\Pi\Sigma\Upsilon\Phi\Psi\Omega$

\bye

Answer 2

With OTF's, one way is to define them with

\Umathcharnumdef\Alpha="0391
\Umathcharnumdef\Beta="0392
% ...
\Umathcharnumdef\Omega="03A9

Answer 3

This fix is not robust to italic, slanted or bold capital Greek letters but should be easily adapted. It loads the missing letters from the original Computer Modern fonts.

\font\greekcapstenrm=cmr10
\font\greekcapssevenrm=cmr7
\font\greekcapsfiverm=cmr5

\newfam\greekcapsfam
\textfont\greekcapsfam=\greekcapstenrm
\scriptfont\greekcapsfam=\greekcapssevenrm
\scriptscriptfont\greekcapsfam=\greekcapsfiverm

\let\tmpGamma=\Gamma \def\Gamma{{\fam\greekcapsfam\tmpGamma}}
\let\tmpDelta=\Delta \def\Delta{{\fam\greekcapsfam\tmpDelta}}
\let\tmpTheta=\Theta \def\Theta{{\fam\greekcapsfam\tmpTheta}}
\let\tmpLambda=\Lambda \def\Lambda{{\fam\greekcapsfam\tmpLambda}}
\let\tmpXi=\Xi \def\Xi{{\fam\greekcapsfam\tmpXi}}
\let\tmpPi=\Pi \def\Pi{{\fam\greekcapsfam\tmpPi}}
\let\tmpSigma=\Sigma \def\Sigma{{\fam\greekcapsfam\tmpSigma}}
\let\tmpUpsilon=\Upsilon \def\Upsilon{{\fam\greekcapsfam\tmpUpsilon}}
\let\tmpPhi=\Phi \def\Phi{{\fam\greekcapsfam\tmpPhi}}
\let\tmpPsi=\Psi \def\Psi{{\fam\greekcapsfam\tmpPsi}}
\let\tmpOmega=\Omega \def\Omega{{\fam\greekcapsfam\tmpOmega}}