The following works for me:

\input luaotfload.sty
\font \myfont =
file:HM_XNiloofar.ttf:language=dflt;script=arab;ccmp=yes;init=yes;medi=yes;fina=yes;rlig=yes
\myfont Salam

\pardir TRT
\textdir TRT
سلام
حسن
\bye


On Fri, Oct 7, 2016 at 7:19 AM, Mohammad Hossein Bateni <bateni@gmail.com>
wrote:

> I don't know much about fontsampler but the commands you list here are
> mostly irrelevant.  My guess is you will need to set the features in the
> font to get proper shaping.  A good set of features that should do the
> trick is called "arabic".
>
> When loading the font, you should do something like the following, but I
> have not tried it myself.
>
> \font\myfont=file:font.otf:language=dflt;script=arab;
> ccmp=yes;init=yes;medi=yes;fina=yes;rlig=yes
>
> —MHB
>
>
> On Fri, Oct 7, 2016 at 7:01 AM, Mingranina Gingranina <
> mingranina@gmail.com> wrote:
>
>> Dear All,
>>  Hello,
>>
>>  I am trying to use "fontsampler example" with Persian fonts (please
>> see below or "http://wiki.luatex.org/index.php/Fontsampler"
>>  for fontsampler codes).
>>  The problem is that Persian words apears as a string of separate
>> glyphs, for example I get "ح‌س‌ن" instead of "حسن".
>>  Do I have to use commands like the followings inside \directlua or
>> tex.tprint to fix the problem? If yes, how can I do that?
>>
>> \installlanguage [fa][default=pe,date=\longjalalidatefmt]
>> \mainlanguage[fa]
>>
>> \definefontfeature[tlig][tlig=yes]
>> \definefontfeature[slanted][slant=.2]
>> \definefontfeature[dlang][language=dflt]
>> \definefontfeature[flang][language=far]
>>
>> Thanks
>> Mingranina
>>
>>
>> fontsampler.tex
>> ============================================================
>> =============================================
>> \input luaotfload.sty
>> \overfullrule 0pt
>> \font\mono = {file:lmmono8-regular.otf} at 6pt
>> \parindent 0pt
>>
>> \def \samplestring {Sphinx of black quartz, judge my vow. 1234567890
>> äÄöÖüÜ ß !"§\$\%\&()=?}
>>
>> \directlua{
>>   dofile("fontsampler.lua")
>>   fontsampler(arg[2])
>> }
>>
>> \bye
>> ============================================================
>> =============================================
>> End Of fontsampler.tex
>>
>>
>> fontsampler.lua
>> ============================================================
>> =============================================
>> function dirtree(dir)
>>   assert(dir and dir ~= "", "directory parameter is missing or empty")
>>   if string.sub(dir, -1) == "/" then
>>     dir=string.sub(dir, 1, -2)
>>   end
>>
>>   local function yieldtree(dir)
>>     for entry in lfs.dir(dir) do
>>       if not entry:match("^%.") then
>>         entry=dir.."/"..entry
>>           if not lfs.isdir(entry) then
>>             coroutine.yield(entry,lfs.attributes(entry))
>>           end
>>           if lfs.isdir(entry) then
>>             yieldtree(entry)
>>           end
>>       end
>>     end
>>   end
>>
>>   return coroutine.wrap(function() yieldtree(dir) end)
>> end
>>
>>
>> function fontsampler( dir )
>>   for entry in dirtree(dir) do
>>     if entry:match(".otf","-4") then
>>       tex.tprint({[[\mono ]]},{-2,entry},{[[
>> (]]},{-2,fontloader.info(entry).fontname},{[[)\par\penalty
>> 10000\font\sample={file:]]},{-2,entry},{[[} at
>> 12pt\sample\samplestring\par\penalty 10000\vrule width \hsize height
>> 0.25pt depth 0pt\par]]})
>>     end
>>   end
>> end
>> ============================================================
>> =============================================
>> End Of fontsampler.lua
>> ____________________________________________________________
>> _______________________
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>>
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>
>
>