使用 tikz 在 beamer 标头中设置多行规则

Question

考虑以下 MWE：

\documentclass{beamer}

\usepackage{tikz}
\usetikzlibrary{arrows,intersections,calc,decorations.pathreplacing,
decorations.markings}
\addtobeamertemplate{frametitle}{}{%
\begin{tikzpicture}[remember picture,overlay]
\node[anchor=south west, yshift=-2pt, xshift=1pt] at (current page.south west)
{};
\draw[blue] ([yshift=-1cm, xshift=0.25cm]current page.north west)
  -- ([yshift=-1cm, xshift=\paperwidth - 0.25cm]current page.north west);
\end{tikzpicture}}

\begin{document}

\begin{frame}
  \frametitle{A shor title}
  Foo
\end{frame}

\begin{frame}
  \frametitle{A terribly long beamer slide title about some obscure meaningless
  topic}
  Bar
\end{frame}

\end{document}

这样我得到以下输出：

所以我的问题是：是否可以使用 tikz（或任何其他包）来生成适应多行框架标题的规则？ 谢谢！

编辑：在我的特定情况下，我需要一个也适用于大写框架标题的解决方案。我目前通过添加以下行来获得它：

\setbeamertemplate{frametitle}{\expandafter\MakeUppercase\expandafter\insertframetitle}

Answer 1

使用tikz它来绘制一个简单的规则听起来有点过度 - 我只需执行以下操作：

\documentclass{beamer}

\setbeamercolor{separation line}{bg=red}

\makeatletter
\setbeamertemplate{frametitle}{
  \ifbeamercolorempty[bg]{frametitle}{}{\nointerlineskip}%
  \@tempdima=\textwidth%
  \advance\@tempdima by\beamer@leftmargin%
  \advance\@tempdima by\beamer@rightmargin%
  \begin{beamercolorbox}[sep=0.3cm,left,wd=\the\@tempdima]{frametitle}
    \usebeamerfont{frametitle}%
    \vbox{}\vskip-1ex%
    \if@tempswa\else\csname beamer@fteleft\endcsname\fi%
    \strut\MakeUppercase{\insertframetitle}\strut\par%
    {%
      \ifx\insertframesubtitle\@empty%
      \else%
      {\usebeamerfont{framesubtitle}\usebeamercolor[fg]{framesubtitle}\insertframesubtitle\strut\par}%
      \fi
    }%
    \vskip-1ex%
    \if@tempswa\else\vskip-.3cm\fi% set inside beamercolorbox... evil here...
  \end{beamercolorbox}%
  \begin{beamercolorbox}[sep=0.3cm,wd=\the\@tempdima]{frametitle}
     \hrulefill\hspace*{0cm}
  \end{beamercolorbox}
}
\makeatother

\begin{document}

\begin{frame}
  \frametitle{A shor title}
  Foo
\end{frame}

\begin{frame}
  \frametitle{A terribly long beamer slide title about some obscure meaningless
  topic}
  Bar
\end{frame}

\end{document}

---

TIKZ 解决方案

\documentclass{beamer}
\usepackage{tikz}

\setbeamercolor{separation line}{bg=red}

\makeatletter
\addtobeamertemplate{frametitle}{}{
    \begin{beamercolorbox}[sep=0.3cm,wd=\the\@tempdima]{frametitle}
       \begin{tikzpicture}
        \draw[structure.fg] (0,0) -- (12.2,0);
       \end{tikzpicture}
    \end{beamercolorbox}
}
\makeatother

\begin{document}

\begin{frame}
  \frametitle{A shor title}
  Foo
\end{frame}

\begin{frame}
  \frametitle{A terribly long beamer slide title about some obscure meaningless
  topic}
  Bar
\end{frame}

\end{document}