XeLaTeX + kpfonts + Greek

Question

Because of this question, I'm using the following code to typeset my XeLaTeX document. The problem is, there does not seem to be any support for Greek. The Greek text in the following comes out as question marks:

\documentclass{memoir}

\usepackage{fontspec}
\usepackage[T1]{fontenc}
\usepackage[oldstylenums]{kpfonts}

\usepackage{polyglossia}

\begin{document}

Some nice Greek text in the middle of an English document: μυϱίᾳ εἰμὶ διὰ τὴν τοῦ ϑεοῦ λατϱείαν.

\end{document}

I looked into this question, too, and hence tried to add the line

\newfontfamily\greekfont[Script=Greek]{Linux Libertine O}

to the preamble, but it changed nothing.

Answer 1

If you want to use the kpfonts for text, then XeLaTeX is out of the question: they don't have support for OpenType or TrueType and so they aren't suitable for usage with XeLaTeX (although some dirty tricks might work).

Here's a version for pdflatex with babel, where for Greek I use GFS Artemisia that's not so distant from the Kpfonts.

\documentclass[a4paper]{memoir}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[greek,danish]{babel}

\usepackage{amsmath}
\usepackage{kpfonts} % for math
\usepackage{substitutefont}
\substitutefont{LGR}{\rmdefault}{artemisia}
\usepackage{siunitx}

\begin{document}

København er Danmarks hovedstad og er med \num{1246611} indbyggere (2014) 
landets største byområde omfattende 18 kommuner eller dele heraf. Centrum
for byområdet udgøres af Københavns Kommune, der inkl. enklaven
Frederiksberg Kommune tæller \num{661464} indbyggere (2013) og er Danmarks 
mest folkerige kommune. I hele byregionen, den \SI{2778}{km^2} store 
Hovedstadsregionen, bor \num{1950430} mennesker (2013), der også
sammenfalder med Københavns lokaltrafikområde. Den danske hovedstad er
desuden centrum for Øresundsregionen, som er Nordens største metropolregion. 
\[
\int_{-\infty}^\infty e^{-x^2}\,dx=\sqrt{\pi}
\]
\textgreek{μυρίᾳ εἰμὶ διὰ τὴν τοῦ θεοῦ λατρείαν}.

\end{document}

For XeLaTeX, probably the best match is Palatino or a clone thereof (TeX Gyre Pagella, here) again with GFS Artemisia for Greek.

\documentclass[a4paper]{memoir}

\usepackage{amsmath}
\usepackage{unicode-math}
\usepackage{polyglossia}
\usepackage{siunitx}

\setmainfont{TeX Gyre Pagella}
\setmathfont{TeX Gyre Pagella Math}
\setmainlanguage{danish}
\setotherlanguage{greek}
\newfontfamily{\greekfont}{GFS Artemisia}

\begin{document}

København er Danmarks hovedstad og er med \num{1246611} indbyggere (2014) 
landets største byområde omfattende 18 kommuner eller dele heraf. Centrum
for byområdet udgøres af Københavns Kommune, der inkl. enklaven
Frederiksberg Kommune tæller \num{661464} indbyggere (2013) og er Danmarks 
mest folkerige kommune. I hele byregionen, den \SI{2778}{km^2} store 
Hovedstadsregionen, bor \num{1950430} mennesker (2013), der også
sammenfalder med Københavns lokaltrafikområde. Den danske hovedstad er
desuden centrum for Øresundsregionen, som er Nordens største metropolregion. 
\[
\int_{-\infty}^\infty e^{-x^2}\,dx=\sqrt{\pi}
\]
\textgreek{μυρίᾳ εἰμὶ διὰ τὴν τοῦ θεοῦ λατρείαν}.

\end{document}

Answer 2

Here if you want to use greek from another font. Your selection Linux Libertine O has all glyphs mentioned.

\documentclass{memoir}
\usepackage{polyglossia}
\setmainlanguage[spelling=new]{german}
\setotherlanguage[variant=polytonic]{greek}
\setotherlanguage{english}
\usepackage{fontspec}
\usepackage[T1]{fontenc}
\usepackage[oldstylenums]{kpfonts}
\newfontfamily{\greekfont}[Ligatures=TeX]{Linux Libertine O}

\begin{document}

Some nice Greek text in the middle of an English document: \textgreek{μυϱίᾳ εἰμὶ διὰ   τὴν τοῦ ϑεοῦ λατϱείαν}. Yes in the middle.

\end{document}

Note: If you don't want to always type \textgreek you could define every symbol like in the code below e.g.: \newunicodechar{α}{\textgreek{α}}

If you say: well I only use the standard greek symbols, no special, you can use the few shipped with kpfonts:

\documentclass{memoir}
\usepackage{fontspec}
\usepackage[T1]{fontenc}
\usepackage[oldstylenums]{kpfonts}
\usepackage{polyglossia}

\usepackage{newunicodechar}

\newunicodechar{α}{$\alphaup$}
\newunicodechar{β}{$\betaup$}
\newunicodechar{γ}{$\gammaup$}
\newunicodechar{δ}{$\deltaup$}
\newunicodechar{ε}{$\varepsilonup$} %\epsilonup your choice
\newunicodechar{ζ}{$\zetaup$}
\newunicodechar{η}{$\etaup$}
\newunicodechar{ϑ}{$\thetaup$}
\newunicodechar{ι}{$\iotaup$}
\newunicodechar{κ}{$\kappaup$}
\newunicodechar{λ}{$\lambdaup$}
\newunicodechar{μ}{$\muup$}
\newunicodechar{ν}{$\nuup$}
\newunicodechar{ξ}{$\xiup$}
\newunicodechar{ℴ}{o}
\newunicodechar{π}{$\piup$}
\newunicodechar{ν}{$\rhoup$}
\newunicodechar{σ}{$\sigmaup$}
\newunicodechar{τ}{$\tauup$}
\newunicodechar{φ}{$\varphiup$} %\phiup your choice
\newunicodechar{χ}{$\chiup$}
\newunicodechar{ψ}{$\psiup$}
\newunicodechar{ω}{$\omegaup$}
\newunicodechar{τ}{$\tauup$}

\begin{document}
Some nice reduced Greek text in the middle of an English document: αβγδεζη...
\end{document}