%%%%%%
\definefontfeature
   [fea]
   [mode=node,language=dflt,script=arab,
    init=yes,medi=yes,fina=yes,isol=yes,
    liga=yes,dlig=yes,rlig=yes,clig=yes,
    mark=yes,mkmk=yes,kern=yes,curs=yes]

\starttypescript [serif] [arabtype]
 \definefontsynonym [Arabtype-Light]       [name:ArabicTypesetting] [features=fea]
 \definefontsynonym [Arabtype-Bold]        [name:ArabicTypesetting] [features=fea]
 \definefontsynonym [Arabtype-Italic]      [name:ArabicTypesetting] [features=fea]
 \definefontsynonym [Arabtype-Bold-Italic] [name:ArabicTypesetting] [features=fea]
\stoptypescript

\starttypescript [serif] [arabtype]
 \usetypescript[serif][fallback]
 \definefontsynonym [Serif]                [Arabtype-Light]         [features=fea]
 \definefontsynonym [SerifItalic]          [Arabtype-Italic]        [features=fea]
 \definefontsynonym [SerifBold]            [Arabtype-Bold]          [features=fea]
 \definefontsynonym [SerifBoldItalic]      [Arabtype-Bold-Italic]   [features=fea]
\stoptypescript

\starttypescript [Arabtype]
  \definetypeface [Arabtype] [rm] [serif] [arabtype] [default] 
\stoptypescript 
%%%%%%

\usetypescript[Arabtype]
%\setupbodyfont[Arabtype,20pt]

\definefontfallback [ara] [Arabtype] [arabic] [force=yes]
\definefontsynonym[Arabicserif][Serif][fallbacks=ara]

% This doesn't render Arabic
%\definefontsynonym[Arabicserif][Serif][fallbacks=ara,features=fea]

% This doesn't use the fallback featue, so is OK
\definefont[ArabType][Arabtype*fea]

% This renders Arabic, but no OpenType features
\definefont[Arabic][Arabicserif]

% This doesn't render Arabic too
\definefont[ArabicFea][Arabicserif*fea]

\startbuffer[salah]
\textdir TRT\pardir TRT
اللَّهُمَّ صَلِّ عَلَى مُحَمَّدٍ وَآلِ مُحَمَّدٍ وَ ارْزُقْنِي الْيَقِينَ وَ حُسْنَ الظَّنِّ بِكَ
وَ أَثْبِتْ رَجَاءَكَ فِي قَلْبِي وَ اقْطَعْ رَجَائِي عَمَّنْ سِوَاكَ حَتَّى لَا أَرْجُوَ
 غَيْرَكَ وَ لَا أَثِقَ إِلَّا بِك

\textdir TLT\pardir TLT
\input knuth
\stopbuffer

\starttext
\ArabType\getbuffer[salah]
\hrule
\Arabic\getbuffer[salah]
\hrule
\ArabicFea\getbuffer[salah]
\stoptext