Robert's answer with babel, added \arbboxi, \arbboxr, \arbboxl and \arbboxb for isolated, beginning, end, middle form of letters. boxes are drawn with TikZ you can customize them with boxstyle as you like using \tikzset{boxstyle/.append style={...}}
\documentclass[a4paper,12pt,twoside]{book}
\usepackage [bidi=basic,layout=lists.tabular]{babel}
\babelprovide[import=ar,mapdigits,main]{arabic}
\babelfont{rm}{Amiri}
\usepackage{tikz}
\usepackage{ulem}
\newcommand{\ulinei}[1]{\uline{#1}}
\newcommand{\ulinel}[1]{^^^^200d\uline{^^^^200d#1}}
\newcommand{\uliner}[1]{\uline{#1^^^^200d}^^^^200d}
\newcommand{\ulineb}[1]{^^^^200d\uline{^^^^200d#1^^^^200d}^^^^200d}
\tikzset{boxstyle/.style={draw=red,inner sep=0pt,fill=yellow}}
\newcommand{\arbboxi}[1]{%
\tikz[baseline=(x.base)]\node(x)[boxstyle]{#1};%
}
\newcommand{\arbboxl}[1]{%
^^^^200d\tikz[baseline=(x.base)]\node(x)[boxstyle]{^^^^200d#1};%
}
\newcommand{\arbboxr}[1]{%
\tikz[baseline=(x.base)]\node(x)[boxstyle]{#1^^^^200d};^^^^200d%
}
\newcommand{\arbboxb}[1]{%
^^^^200d\tikz[baseline=(x.base)]\node(x)[boxstyle]{^^^^200d#1^^^^200d};^^^^200d%
}
\begin{document}
\Large
جنوب
\hrulefill
\uliner{ج}نوب
ج\ulineb{ن}وب
جن\ulinel{و}ب
جنو\ulinei{ب}
\hrulefill
\arbboxr{ج}نوب
ج\arbboxb{ن}وب
جن\arbboxl{و}ب
جنو\arbboxi{ب}
\tikzset{boxstyle/.append style={dashed,draw=blue,font=\bfseries,fill=green}}
\hrulefill
\arbboxr{ج}نوب
ج\arbboxb{ن}وب
جن\arbboxl{و}ب
جنو\arbboxi{ب}
\end{document}
Update 24/02/2020
I have created a command \FormatChar (thanks to @David Carlisle https://tex.stackexchange.com/a/529439/54817)
you can apply any commands for a character in Arabic word, the command can also be used with xelatex.
\documentclass[a4paper,12pt,twoside]{book}
\usepackage [bidi=basic,layout=lists.tabular]{babel}
\babelprovide[import=ar,mapdigits,main]{arabic}
\babelfont{rm}{Amiri}
\usepackage{tikz}
\usepackage{ulem}
\def\connecti{i}
\def\connectr{r}
\def\connectl{l}
\def\connectb{b}
\makeatletter
\def\FormatChar#1#2#3#4{%
\let\joineri@firstofone%
\let\joinerii@firstofone%
\def\formatcs{#1}%
\def\temp{#3}%
\if\temp\connectb%
\else
\if\temp\connectr%
\let\joinerii@gobble%
\else
\if\temp\connectl%
\let\joineri@gobble%
\else
\if\temp\connecti%
\let\joineri@gobble\let\joinerii@gobble%
\else
@latex@error
{\temp is not available for contextual forms}
\fi%
\fi%
\fi%
\fi%
\xFormatChar{#2}#4}%
\def\xFormatChar#1#2{\ifnum#1=1\joineri{^^^^200d}%
\formatcs{\joineri{^^^^200d}#2\joinerii{^^^^200d}}%
\joinerii{^^^^200d}\expandafter@gobbletwo%
\else#2\fi\xFormatChar{\numexpr#1-1\relax}}
\makeatother
\tikzset{charboxstyle/.style={draw=red,inner sep=0pt,fill=yellow}}
\newcommand{\charbox}[1]{%
\tikz[baseline=(x.base)]\node(x)[charboxstyle]{#1};%
}
\begin{document}
%\FormatChar{#1}{#2}{#3}{#4}
% #1: Command
% #2: Position of char (number)
% #3: Contextual forms r , l , b , i
% #4: Word
\Huge
\FormatChar{\uline}{1}{l}
{جنوب}
%
\FormatChar{\textcolor{blue}}{2}{b}
{جنوب}
%
\FormatChar{\textcolor{red}}{3}{r}
{جنوب}
%
\FormatChar{\charbox}{4}{i}
{جنوب}
%
\tikzset{charboxstyle/.append style={dashed,draw=blue,fill=green,text=orange}}
%
\FormatChar{\charbox}{1}{l}
{جنوب}
\end{document}
Update 28/02/2020
For multiple letters macro \FormatChars can be used (thanks to @egreg https://tex.stackexchange.com/a/529602/54817 )
\documentclass{article}
\usepackage{tikz}
\usepackage{xparse}
\usepackage{ulem}
\usepackage [bidi=basic]{babel}
\babelprovide[import=ar,main]{arabic}
\babelfont{rm}{Amiri}
\tikzset{charboxstyle/.style={draw=red,inner sep=0pt,fill=yellow}}
\newcommand{\charbox}[1]{%
\tikz[baseline=(x.base)]\node(x)[charboxstyle]{#1};%
}
\ExplSyntaxOn
\NewDocumentCommand{\FormatChars}{m >{\SplitArgument{1}{-}}m O{i} m}
{
\cs_set_nopar:Npn \inputcs { #1 }
\cs_set_nopar:Npn \joinb {^^^^200d}
\cs_set_nopar:Npn \joine {^^^^200d}
\str_case:nnF { #3 }
{
{ i } { \let\joinb\relax\let\joine\relax }
{ r } { \let\joine\relax }
{ l } { \let\joinb\relax }
{ b } { }
}
{
\msg_error:nn {}{#2~is~not~available~for~contextual~forms,~try~with~r,~l,~or~b}
}
% #2 is passed as two braced arguments
_FormatChars:nnn #2 { #4 }
}
\cs_new_protected:Nn _FormatChars:nnn
{
% let's analyze the first two args
\tl_if_novalue:nTF { #2 }
{% no hyphen in the argument
___FormatChars:nnn { #1 } { #1 } { #3 }
}
{
\bool_lazy_or:nnTF { \tl_if_blank_p:n { #1 } } { \tl_if_blank_p:n { #2 } }
{% argument is -n or m- or -
\tl_if_blank:nTF { #1 }
{
\tl_if_blank:nTF { #2 }
{% argument is -
\joinb\inputcs{\joinb #3\joine}\joine
}
{% argument is -n
___FormatChars:nnn { 1 } { #2 } { #3 }
}
}
{% argument is m-
___FormatChars:nnn { #1 } { -1 } { #3 }
}
}
{% argument is m-n
___FormatChars:nnn { #1 } { #2 } { #3 }
}
}
}
\cs_new_protected:Nn ___FormatChars:nnn
{
\int_compare:nTF { #1 > #2 > 0 }
{
#3
}
{
\tl_range:nnn { #3 } { 1 } { #1 - 1 }
\joinb\inputcs{\joinb \tl_range:nnn { #3 } { #1 } { #2 }\joine }\joine
\tl_range:nnn { #3 } { #2 + 1 } { -1 }
}
}
\ExplSyntaxOff
\begin{document}
%\FormatChars{#1}{#2}[#3]{#4}
% #1 : command to apply on range ex : \uline
% #2 : range of letters ex : 2-6
% #3 : type of connection : i , r , l , b (default i)
% #4 : word
\Huge
\FormatChars{\uline}{1-3}
{جنوب}
%
\FormatChars{\textcolor{blue}}{2-3}[r]
{جنوب}
%
\FormatChars{\textcolor{red}}{2-}[r]
{جنوب}
%
\FormatChars{\charbox}{4}
{جنوب}
%
\tikzset{charboxstyle/.append style={draw=blue,fill=black,text=white}}
%
\FormatChars{\charbox}{-2}[l]
{جنوب}
\end{document}
soulpackage use a font which does not contain Arabic script. – Salim Bou Feb 13 '20 at 20:19lua. – Salim Bou Feb 13 '20 at 20:40