我需要能够检查 pgfkey 的值是否为空。我尝试过的解决方案（使用包etoolbox）：
\edef\temp{\pgfkeysvalueof{/path/key}}%
\expandafter\ifstrequal\expandafter{\temp}{}{key is empty}{key is not empty}%
但是如果键的值扩展为空或更糟，则此方法不起作用：键的值无法扩展！如何在不扩展键的情况下检查键是否为空？我只想检查它的字符串值是否等于“”。
编辑：添加了一个完整的示例
\documentclass{article}
\usepackage{tikz}
\usepackage{etoolbox}
\usepackage{overpic}
\newcommand{\strcomp}{\expandafter\ifstrequal\expandafter}%
\pgfkeys{
/icon/.cd,
width/.initial,
overlay/.initial,
}
\newcommand{\icon}[2][]{%
{%
\pgfkeys{/icon/.cd,width,overlay,#1}%
\def\options{}%
\edef\temp{\pgfkeysvalueof{/icon/width}}%
\strcomp{\temp}{}{}{\edef\options{width=\pgfkeysvalueof{/icon/width},\options}}%
\edef\temp{\pgfkeysvalueof{/icon/overlay}}%
\strcomp{\temp}{}{%
\edef\graphic{\noexpand\includegraphics[\options]{#2}}%
}{%
\edef\temp{\noexpand\begin{overpic}[\options]{#2}}%
\def\graphic{\temp\put(0,0){\pgfkeysvalueof{/icon/overlay}}\end{overpic}}%
}%
\graphic
}%
}%
\begin{document}
\icon{example-image} % Works!
\icon[width=3cm]{example-image} % Works :)
\icon[width=3cm,overlay=jei]{example-image} % Also works :)
\icon[width=3cm,overlay={\includegraphics{overlay-image}}]{example-image} % Breaks down when trying to expand in \edef\temp{\pgfkeysvalueof{/icon/overlay}}
\end{document}
答案1
当未设置键时，值是\pgfkeysemptyvalue，因此您需要将值与此进行比较。一种方法是使用\ifdefequal：
\documentclass{article}
\usepackage{tikz}
\usepackage{etoolbox}
\usepackage{overpic}
\pgfkeys{
/icon/.cd,
width/.initial,
overlay/.initial,
}
\newcommand{\icon}[2][]{%
{%
\pgfkeys{/icon/.cd,width,overlay,#1,width/.get=\temp}%
\def\tempa{\pgfkeysnovalue}
\def\options{}%
\ifdefequal{\temp}{\tempa}{}{\edef\options{width=\temp,\options}}%
\pgfkeysgetvalue{/icon/overlay}{\temp}%
\ifdefequal{\temp}{\tempa}{%
\edef\graphic{\noexpand\includegraphics[\options]{#2}}%
}{%
\edef\temp{\noexpand\begin{overpic}[\options]{#2}}%
\def\graphic{\temp\put(0,0){\pgfkeysvalueof{/icon/overlay}}\end{overpic}}%
}%
\graphic
}%
}%
\begin{document}
\icon{example-image}
\icon[width=3cm]{example-image}
\icon[width=3cm,overlay=jei]{example-image}
\icon[width=3cm,overlay={\includegraphics{example-image-a}}]{example-image}
\end{document}