错误信息：
LaTeX Warning: Command \markboth has changed.
Check if current package is valid.
LaTeX Warning: Command \markright has changed.
Check if current package is valid.
) (./hello.aux)
*geometry* driver: auto-detecting
*geometry* detected driver: xetex
ABD: EveryShipout initializing macros
Chapter 1.
Underfull \hbox (badness 10000) in paragraph at lines 39--47
Underfull \hbox (badness 10000) in paragraph at lines 39--47
Underfull \hbox (badness 10000) in paragraph at lines 39--47
[1]
! Missing { inserted.
<to be read again>
}
l.48 \section[Section One]{Section First}
我的全部代码：
\documentclass[a4paper,12pt]{book}
\usepackage[a4paper, inner=1cm, outer=2cm, top=3cm, bottom=3cm, bindingoffset=2cm]{geometry}
\usepackage[english]{babel}
\usepackage{blindtext, graphicx, wrapfig, enumitem, fancyhdr, extramarks, amsmath, tikz, fontawesome, lipsum}
\usepackage{fontspec}
\setmainfont{Ubuntu}
\setmonofont{Ubuntu Mono}
\newfontfamily{\FAS}{Font Awesome 5 Free Solid}
\newfontfamily{\FAR}{Font Awesome 5 Free Regular}
\newfontfamily{\FAB}{Font Awesome 5 Brands Regular}
\usepackage{xcolor}
\makeatletter
\newcommand{\globalcolor}[1]{%
\color{#1}\global\let\default@color\current@color
}
\makeatother
\AtBeginDocument{\globalcolor{white}}
\usepackage[pages=all]{background}
\backgroundsetup{
scale=1,color=black,opacity=0.10,angle=0,contents={
\includegraphics[height=15cm]{logo.png}
}
}
\usepackage{index}
\makeindex
\begin{document}
\BgThispage
\pagecolor{darkgray}
\chapter[Chapter OnE]{Chapter FiRsT}
This is some text in the regular font.\\\\
{\texttt{This is Typed in Ubuntu Mono.}}\\\\
{\FAS{\symbol{"F0E0}}}\\
{\FAS{\symbol{"F3C5}}}\\
{\FAS{\symbol{"F095}}}\\
{\FAS{\symbol{"F57D}}}\\\\
\blindmathtrue
\Blindtext[5]
\section[Section One]{Section First}
\Blindtext[6]
\section[Section TwO]{Section SeCoNd}
\Blindtext[6]
\chapter[Chapter TwO]{Chapter SeCoNd}
\Blindtext[5]
\end{document}
答案1
该包index与不兼容extramarks，因为后者需要的命令与前者要执行的操作相冲突。
有更好的方法来支持多个索引，但我不推荐index，它已经十五年没有维护了，仍然宣传是 4.2beta 版本，并对一些重要命令进行了重新定义，使得它与其他软件包不兼容。
请注意，这\\不是结束段落的方式，结束段落的方式是通过留下一个空行。
对于没有变体的字体，也\newfontface应该选择：\newfontfamily
\newfontface{\fasfont}{Font Awesome 5 Free Solid}
\NewDocumentCommand{\FAS}{m}{{\normalfont\fasfont\symbol{#1}}}
并且\FAS{"F0E0}将更加健壮和简单。