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Beamer footline 与 ifnum 和帧号的奇怪交互

tag-icon • tag-icon tikz-pgf beamer luatex
Beamer footline 与 ifnum 和帧号的奇怪交互

我正在为除第一张幻灯片外的所有幻灯片显示进度条创建一个主题。我将进度条放在脚注中，因为我希望它显示在底部。

我不明白为什么这不起作用（实际上如果你大量放大它会显示一个非常小的进度条）

\ifnum\insertframenumber>1\relax%
%progress bar code
\fi

这有效

\ifnum\insertframenumber=1\relax%
\else
%progress bar code
\fi

另一个问题是，如果我不添加\ifnum\inserttotalframenumber>1，它将在第一次运行时失败，但在后续运行中可以正常工作。似乎 latex 在第一次运行中编译了两次代码，第一次编译的 \inserttotalframenumber 等于 1（导致除以 0）。这是正确的吗？

我把代码放在下面。有注释表示有效代码和无效代码。它是用 Luatex 编译的。我不确定 pdflatex 是否能工作。

% filename: beamerouterthemetest.sty
\mode<presentation>

\RequirePackage{tikz}

\newcount\progressbar@current
\newcount\progressbar@total
\newdimen\progressbar@curwidth
\newdimen\progressbar@width
\newdimen\progressbar@height

\progressbar@width=\paperwidth
\progressbar@height=1mm

% the progress bar
\def\progressbar@progressbar{%
    \progressbar@current=\insertframenumber
    \progressbar@total=\inserttotalframenumber
    \advance\progressbar@current-1
    \advance\progressbar@total-1
    
    \progressbar@curwidth=\progressbar@width
    \multiply\progressbar@curwidth by \progressbar@current
    \divide\progressbar@curwidth by \progressbar@total

  \begin{tikzpicture}[]
      \draw[fill=fg] %
        (0pt, 0pt) rectangle ++ (\progressbar@curwidth, \progressbar@height);
  \end{tikzpicture}%
}

% THIS WORKS!!!!!!!!!!!!!!!!!!!
% Footline
\defbeamertemplate*{footline}{test}[1][] {
  \ifnum\insertframenumber=1\relax%
  \else
    % Added next ifnum to avoid division by 0 crash in first run
    \ifnum\inserttotalframenumber>1\relax%
      \begin{beamercolorbox}[wd=\paperwidth]{progressbar}%
        \progressbar@progressbar%
      \end{beamercolorbox}%
    \fi
  \fi
}

% THIS DOESNT WORK!!!!!!!!!!!!!!!!!!!
% % Footline
% \defbeamertemplate*{footline}{test}[1][] {
%   \ifnum\insertframenumber>1\relax%
%     % Added next ifnum to avoid division by 0 crash in first run
%     \ifnum\inserttotalframenumber>1\relax%
%       \begin{beamercolorbox}[wd=\paperwidth]{progressbar}%
%         \progressbar@progressbar%
%       \end{beamercolorbox}%
%     \fi
%   \fi
% }

\mode<all>


% filename: test-example.tex
\documentclass[aspectratio=169]{beamer}
\useoutertheme{test} 

\begin{document}
\begin{frame}{Slide 1}
\end{frame}
\begin{frame}{Slide 2}
\end{frame}
\begin{frame}{Slide 3}
\end{frame}
\begin{frame}{Slide 4}
\end{frame}
\begin{frame}{Slide 5}
\end{frame}
\begin{frame}{Slide 6}
\end{frame}
\begin{frame}{Slide 7}
\end{frame}

\end{document}

答案1

问题在于，beamer 在文档开头计算了框架几何形状，包括页脚线的高度。此时，框架编号显然不会大于 1，因此页脚高度计算为 0pt，因此页脚线不可见。

您可以通过确保页脚在文档开头具有合适的高度来避免此问题：

% filename: test-example.tex
\documentclass[aspectratio=169]{beamer}

\makeatletter
% filename: beamerouterthemetest.sty
\mode<presentation>

\RequirePackage{tikz}

\newcount\progressbar@current
\newcount\progressbar@total
\newdimen\progressbar@curwidth
\newdimen\progressbar@width
\newdimen\progressbar@height

\progressbar@width=\paperwidth
\progressbar@height=1mm

% the progress bar
\def\progressbar@progressbar{%
    \progressbar@current=\insertframenumber
    \progressbar@total=\inserttotalframenumber
    \advance\progressbar@current-1
    \advance\progressbar@total-1
    
    \progressbar@curwidth=\progressbar@width
    \multiply\progressbar@curwidth by \progressbar@current
    \divide\progressbar@curwidth by \progressbar@total

  \begin{tikzpicture}[]
      \draw[fill=fg] %
        (0pt, 0pt) rectangle ++ (\progressbar@curwidth, \progressbar@height);
  \end{tikzpicture}%
}

%% THIS WORKS!!!!!!!!!!!!!!!!!!!
%% Footline
%\defbeamertemplate*{footline}{test}[1][] {
%  \ifnum\insertframenumber=1\relax%
%  \else
%    % Added next ifnum to avoid division by 0 crash in first run
%    \ifnum\inserttotalframenumber>1\relax%
%      \begin{beamercolorbox}[wd=\paperwidth]{progressbar}%
%        \progressbar@progressbar%
%      \end{beamercolorbox}%
%    \fi
%  \fi
%}

% THIS DOESNT WORK!!!!!!!!!!!!!!!!!!!
 % Footline
 \defbeamertemplate*{footline}{test}[1][] {
   \ifnum\insertframenumber>1%
     % Added next ifnum to avoid division by 0 crash in first run
     \ifnum\inserttotalframenumber>1\relax%
       \begin{beamercolorbox}[wd=\paperwidth]{progressbar}%
         \progressbar@progressbar%
       \end{beamercolorbox}%
     \fi
   \else
      \vskip0.2cm
   \fi
 }

\mode<all>


\makeatother

\begin{document}
\begin{frame}{Slide 1}
\end{frame}
\begin{frame}{Slide 2}
\end{frame}
\begin{frame}{Slide 3}
\end{frame}
\begin{frame}{Slide 4}
\end{frame}
\begin{frame}{Slide 5}
\end{frame}
\begin{frame}{Slide 6}
\end{frame}
\begin{frame}{Slide 7}
\end{frame}

\end{document}

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