On Tue, Jun 18, 2019 at 11:17 PM Ulrike Fischer <luatex@nililand.de> wrote:
Am Tue, 18 Jun 2019 22:45:18 +0200 schrieb luigi scarso:

>> Is there some documentation available how to access harfbuzz from Lua
>> (jit) / FFI?
>>
>> Patrick
>>
>>
> Well, look at
> luatexdir/luaharfbuzz
> I have also used
> https://github.com/khaledhosny/harf
> to check
> %% test2-latex.tex
> \documentclass{article}
> \usepackage{fontspec}
> \newfontfamily\deva[Script=Devanagari]{NotoSansDevanagari-Regular.ttf}

After I understood that the format is currently only found if it is
in the current folder I could test it.

sure  


Like with harftex you have to use harfload and activate the harf
mode to get the right output.


ok, so you want all ....

\pdfvariable suppressoptionalinfo \numexpr1+32+64+128+512\relax
\pdfvariable compresslevel 0
\pdfvariable objcompresslevel 0

\documentclass{article}

\usepackage{harfload}
\usepackage{setspace}
\usepackage{fontspec}
\usepackage{graphicx}

\defaultfontfeatures{RawFeature={mode=harf}}

\newfontfamily\deva[Script=Devanagari]{NotoSansDevanagari-Regular.ttf}
\newfontfamily\beng[Script=Bengali]{NotoSansBengali-Regular.ttf}
\newfontfamily\guru[Script=Gurmukhi]{NotoSansGurmukhi-Regular.ttf}
\newfontfamily\gujr[Script=Gujarati]{NotoSansGujarati-Regular.ttf}
\newfontfamily\orya[Script=Oriya]{NotoSansOriya-Regular.ttf}
\newfontfamily\taml[Script=Tamil]{NotoSansTamil-Regular.ttf}
\newfontfamily\telu[Script=Telugu]{NotoSansTelugu-Regular.ttf}
\newfontfamily\knda[Script=Kannada]{NotoSansKannada-Regular.ttf}
\newfontfamily\mlym[Script=Malayalam]{NotoSansMalayalam-Regular.ttf}
\newfontfamily\Sinh[Script=Sinhala]{NotoSansSinhala-Regular.ttf}


\begin{document}
luatex with Harfbuzz:

{\deva क्रर्कि} % krarki
{\beng ক্রর্কি} % krarki
{\guru ਕ੍ਰਰ੍ਕਿ} % krarki
{\gujr ક્રર્કિ} % krarki
{\orya କ୍ରର୍କି} % krarki
{\taml கோ} % ko
{\telu క్రర్కి} % krarki
{\knda ಕ್ರರ್ಕಿ} % krarki
{\mlym ക്രര്കി} % krarki
{\Sinh කෙ} % ke

\vskip 1em

XeLaTeX:

\hbox{\hskip5pt\includegraphics[width=8.5cm]{b0miX.png}}

\end{document}

copy the image from 
https://i.stack.imgur.com/b0miX.png

(note \Sinh  vs \sinh)


--
luigi