數學模式下帶有警報的奇怪行為

Question

當我將顏色更改為alerted textin時，我得到了這種意外的行為mathmode。特別是，alerted text.fg似乎只有\alert再次呼叫時才會改變。更改\colorlet只會影響裡面的顏色mathmode。

這是一個例子

\documentclass{beamer}
\begin{document}    
\begin{frame}{Title}
    $\begingroup\setbeamercolor{alerted text}{fg=blue}\alert{blue}\endgroup+\textcolor{alerted text.fg}{red}$  These should be \textcolor{alerted text.fg}{red}, \alert{red} and \textcolor{alerted text.fg}{red}
    
    $\begingroup\setbeamercolor{alerted text}{fg=blue}\alert{blue}\endgroup\setbeamercolor{alerted text}{fg=red}+\textcolor{alerted text.fg}{red}$  These should be \textcolor{alerted text.fg}{red}, \alert{red} and \textcolor{alerted text.fg}{red}
    
    $\begingroup\setbeamercolor{alerted text}{fg=blue}\alert{blue}\endgroup\setbeamercolor{alerted text}{fg=red}\colorlet{alerted text.fg}{red}+\textcolor{alerted text.fg}{red}$  These should be \textcolor{alerted text.fg}{red}, \alert{red} and \textcolor{alerted text.fg}{red}
    
    $\begingroup\setbeamercolor{alerted text}{fg=blue}\alert{blue}\endgroup\setbeamercolor{alerted text}{fg=red}\alert{}+\textcolor{alerted text.fg}{red}$  These should be \textcolor{alerted text.fg}{red}, \alert{red} and \textcolor{alerted text.fg}{red}
\end{frame}

\end{document}

Answer 1

\setbeamercolor{}{}本身尚未創建.fg和.bg顏色，它們僅在使用投影機顏色時創建。

但是，您不必來回更改警報顏色，而是可以使用您喜歡的任何顏色創建更多類似警報的巨集 - 或簡單地使用\structure，預設為藍色。

\documentclass{beamer}

\setbeamercolor{foo}{fg=green}

\newenvironment<>{fooenv}{\begin{altenv}#1%
    {\usebeamercolor[fg]{foo}\usebeamerfont{foo}\usebeamertemplate{foo text begin}}
    {\usebeamertemplate{foo text end}}{\color{.}}{}\ignorespaces}{\ifhmode\unskip\fi\end{altenv}}

\newcommand<>{\foo}[1]{\begin{fooenv}#2\relax#1\end{fooenv}}


\begin{document}    
\begin{frame}{Title}
    $\structure{blue}+\textcolor{alerted text.fg}{red}$  These should be \textcolor{alerted text.fg}{red}, \alert{red} and \textcolor{alerted text.fg}{red}
    
    $\foo{green}+\textcolor{alerted text.fg}{red}$  These should be \textcolor{alerted text.fg}{red}, \alert{red} and \textcolor{alerted text.fg}{red}    

\end{frame}

\end{document}