On Fri, May 3, 2013 at 5:20 PM, "H. Özoguz" <h.oezoguz@mmnetz.de> wrote:

Thanks luigi, but it does not work for my characters, see here:

\definefont[tradoa][name:trado*arabic at 20pt] % or file:amiri-regular.ttf*... file:alq.ttf

\directlua{ local function replace_txt (buffer)

buffer=string.gsub(buffer,"اللهِ","اللَّـه") return buffer end
callback.register("process_input_buffer",replace_txt)
}
\starttext
my text {\setupalign[r2l] \tradoa اللَّـه}
\stoptext

"trado" ist just the font "traditional arabic", nearly every system have it, so you should be able to compile this. It does not replace the character.

my fault, sorry.

In the  string library  the function are not unicode aware (of course, I should say...) .