\enabledirectives[otf.analyze.useunicodemarks]

\usemodule[s-fnt-20]

\starttext

\ctxlua{fonts.analyzers.useunicodemarks = true}

\setvariables
  [otftracker]
  [font=amiri-regular,
   features=arabic,
   size=48pt,
   sample={بِسْمِ الله الرحمن الرحيم},
   direction=-1]

% \setvariables
%   [otftracker]
%   [font=amiri-regular,
%    features=arabic,
%    size=48pt,
%    sample={بِسْمِ بسم},
%    direction=-1]

\stoptext
