%%
%% The LaTeX Companion, 3ed
%%
%% Example 9-3-12 on page I-670 in "Accessing all characters of a font".
%%
%% Copyright (C) 2022 Frank Mittelbach
%%
%% It may be distributed and/or modified under the conditions
%% of the LaTeX Project Public License, either version 1.3c
%% of this license or (at your option) any later version.
%%
%% See https://www.latex-project.org/lppl.txt for details.
%%

\documentclass{tlc3exa}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{159.0pt}
%!TEX program = lualatex

  % In the book we undo the setting again, so that the example does not stop
  % with an error during production ... So delete the next line if you want
  % to see what *should* happen ideally.

  \AtBeginDocument{\tracinglostchars=2 }

%StartShownPreambleCommands
\usepackage{fontspec}
\setmainfont{TeX Gyre Pagella} \setsansfont{Optima}
\tracinglostchars=3 % set this to get lost char errors
%StopShownPreambleCommands

\begin{document}
\sffamily Fonts on a Macintosh often contain an Apple
\symbol{"F8FF} symbol, \rmfamily but do not expect the
apple `\symbol{"F8FF}' to show up with other fonts.
\end{document}