And now, thanks to Jonathan, only one page —
% !TeX Program=Ini-XeTeX
\catcode `\ = 10
\catcode `\{ = 1
\catcode `\} = 2
\catcode `\# = 6
\catcode `\^ = 7
\catcode `\^^I = 10
\catcode `\% = 14
\let \bgroup = {
\let \egroup = }
\let \endgraf = \par
\tracingonline = 1
\tracinglostchars = 2
\dimen 10 = 16383.99998 pt
\input showhyphens
\message {\meaning \showhyphens}
\font \tenrm = "Amiri"
\tenrm
\hyphenchar \font = `\‐
\lccode "200D = "200D
\catcode "200D = 11
\patterns {^^^^200d1^^^^200d}
\def \text {foo^^^^200d^^^^200dbar}
\hsize = 0 pt
\vsize = \dimen 10
\noindent \ \text
\showhyphens \text
\end
--
/** Phil./
\def \loop #1\pool {\def \body {#1}\iterate}
\def \iterate {\body \let \next = \iterate \else \let \next = \relax \fi \next}
\let \pool = \fi
\def \showhyphenspace #1
{%
\ifx \valign #1\valign
\else
#1\vadjust {\penalty 1 } \expandafter \showhyphenspace
\fi
}
\def \showhyphens #1%
{%
\begingroup
\showboxbreadth =\dimen 10
\showboxdepth =\dimen 10
\pretolerance = -1
\tolerance = -1
\setbox 2 = \hbox {}%
\setbox 0 = \vbox
\bgroup
\pretolerance = -1
\tolerance = -1
\hbadness = 0
\parfillskip = 0 pt
\hsize = 1 sp
\noindent
\hskip 0 pt
\hfuzz =\dimen 10
\hbadness =\dimen 10
\showhyphenspace #1 {} \endgraf
\loop
\count 0 = 1
\ifnum \lastnodetype = 1
\setbox 4 = \lastbox
\setbox 2 = \hbox {\unhbox 4
\unhbox 2}%
\count 0 = 0
\fi
\ifnum \lastnodetype = 11 \unskip
\count 0 = 0 \fi
\ifnum \lastnodetype = 13
\count 2 = \lastpenalty
\unpenalty
\count 0 = 0
\ifnum \count 2 = 1 \setbox 2
= \hbox { \unhbox 2 }\count 0 = 0 \fi
\fi
\ifnum \count 0 = 0
\pool
\hsize =\dimen 10
\hfuzz = 0 pt
\hbadness 0
\par
\unhbox 2
\par
\egroup
\endgroup
}
