如何在 Beamer 部分导航栏中为当前部分和其他部分使用不同的背景颜色

Question

我使用以下代码创建部分导航栏：

\setbeamercolor{section in head/foot}{bg=blue,fg=white}
\addtobeamertemplate{footline}{%
    \leavevmode%
    \hbox{%
        \begin{beamercolorbox}[wd=\paperwidth,ht=2.25ex,dp=1ex,center]{section in head/foot}%
            \insertsectionnavigationhorizontal{\paperwidth}{}{}
        \end{beamercolorbox}}%

}{}

现在导航栏的背景是蓝色，当前部分是白色字体，其他部分是灰色字体。但是，是否可以为它们设置不同的背景颜色？例如，当前部分的背景为深蓝色，其他部分的背景为浅蓝色？

整个 beamer tex 文件就是这个非常小的文件。

\documentclass{beamer}

\usetheme{Madrid}
\title{Title}
\author{Author}
\date{\today}
\addtobeamertemplate{footline}{%
    \leavevmode%
    \hbox{%
        \begin{beamercolorbox}[wd=\paperwidth,ht=2.25ex,dp=1ex,center]{author in head/foot}%
            \insertsectionnavigationhorizontal{\paperwidth}{}{}
        \end{beamercolorbox}}%

}{}

\begin{document}
\titlepage
\section{Sec 1}
\begin{frame}{Frame Title}{Frame Subtitle}
    Frame contents
    \begin{itemize}
        \item Item 1
        \item Item 2
              \begin{itemize}
                  \item Subitem 2.1
                  \item Subitem 2.2
              \end{itemize}
    \end{itemize}
    This is \textbf{bold text for normal text}.
\end{frame}

\section{Sec 2}
\begin{frame}{Frame Title}{Frame Subtitle}
    \begin{block}{Block}
        This is \textbf{bold text for blocks}.
    \end{block}
    \begin{alertblock}{Alert Block}
        This is \textbf{bold text for alert blocks}.
    \end{alertblock}
    \begin{example}
        This is \textbf{bold text for example blocks}.
    \end{example}
    \begin{block}{}
        \centering
        This is \textbf{bold text for unnamed blocks}.
    \end{block}
\end{frame}

\end{document}

结果是

很容易看出，导航栏中的 sec 1 和 sec 2 似乎属于一个完整的长水平条，它们之间没有任何边界。它们共享相同的背景颜色，只是当前的颜色突出显示。我想为它们设置不同的背景颜色。可以吗？

Answer 1

您可以重新定义section in head/foot (shaded)模板以包含某种颜色框：

\documentclass{beamer}

\usetheme{Madrid}
\title{Title}
\author{Author}
\date{\today}

\addtobeamertemplate{footline}{%
    \leavevmode%
    \hbox{%
        \begin{beamercolorbox}[wd=\paperwidth,ht=2.5ex,dp=1.1ex,center]{author in head/foot}%
            \insertsectionnavigationhorizontal{\paperwidth}{}{\hskip0pt plus1filll}
        \end{beamercolorbox}}%

}{}

\makeatletter
\newcommand{\secwidth}{\dimexpr\paperwidth/\beamer@sectionmax-2\fboxsep\relax}

\setbeamertemplate{section in head/foot}{\colorbox{orange}{\parbox{\secwidth}{\centering\insertsectionhead}}}
\setbeamertemplate{section in head/foot shaded}{\colorbox{cyan}{\parbox{\secwidth}{\centering\insertsectionhead}}}

\def\insertsectionnavigationhorizontal#1#2#3{%
  \hbox to #1{{%
     \def\slideentry##1##2##3##4##5##6{}%
     #2%\hskip.3cm%
     \usebeamerfont{section in head/foot}\usebeamercolor[fg]{section in head/foot}%
     \setbox\beamer@sectionbox=\hbox{}%
     \ht\beamer@sectionbox=1.875ex%
     \dp\beamer@sectionbox=0.75ex%
     \dohead%
     \box\beamer@sectionbox\hfil%\hskip.3cm%
     #3}}}
     
\def\sectionentry#1#2#3#4#5{% section number, section title, page
  \beamer@xpos=0\relax%
  \beamer@ypos=1\relax%
  \beamer@ypos@offset=0\relax%
  \ifnum#5=\c@part%
  \beamer@section@set@min@width%
  \box\beamer@sectionbox\hskip0ex plus 1fill%
  \setbox\beamer@sectionbox=
  \hbox{\def\insertsectionhead{#2}%
    \def\insertsectionheadnumber{#1}%
    \def\insertpartheadnumber{#5}%
    {%
      \usebeamerfont{section in head/foot}\usebeamercolor[fg]{section in head/foot}%
      \ifnum\c@section=#1%
        \hyperlink{Navigation#3}{{\usebeamertemplate{section in head/foot}}}%
      \else%
        \hyperlink{Navigation#3}{{\usebeamertemplate{section in head/foot shaded}}}%
      \fi}%
  }%
  \ht\beamer@sectionbox=1.875ex%
  \dp\beamer@sectionbox=0.75ex%
  \fi\ignorespaces}     
\makeatother

\begin{document}

\section{Sec 1}
\begin{frame}
\end{frame}

\section{Sec 2}
\begin{frame}
\end{frame}

\section{Sec 3}
\begin{frame}
\end{frame}

\end{document}