Beamer：只有剩余足够空间时，如何才在垂直条中显示徽标？

Question

我想在使用 Palo Alto 主题的 beamer 演示文稿中插入一个额外的（除左上角之外的）徽标，以便仅当有足够剩余空间时它才会出现在导航栏中。

实现这一结果的最佳方法是什么？

到目前为止，我已经能够将它放置在所需的位置，但不知道如何让它“消失”，而不是在没有足够空间时被丑陋地切割。

这是一个最小的工作示例（似乎我的发行版中没有 mwe 包，所以我只创建了一个红色方形图像）。

\documentclass{beamer}
\usetheme[hideothersubsections]{PaloAlto} 
\usecolortheme{seahorse}
\setbeamercovered{transparent}

\makeatletter
\setbeamertemplate{sidebar \beamer@sidebarside}
{
\beamer@tempdim=\beamer@sidebarwidth%
\advance\beamer@tempdim by -6pt%
{\usebeamerfont{title in sidebar}%
  \vskip1.5em%
  \hskip3pt%
  \usebeamercolor[fg]{title in sidebar}%
  \insertshorttitle[width=\beamer@tempdim,center,respectlinebreaks]\par%
  \vskip1.25em%
}%
{%
  \hskip3pt%
  \usebeamercolor[fg]{author in sidebar}%
  \usebeamerfont{author in sidebar}%
  \insertshortauthor[width=\beamer@tempdim,center,respectlinebreaks]\par%
  \vskip1.25em%
}%
\insertverticalnavigation{\beamer@sidebarwidth}%
\vfill
\ifx\beamer@sidebarside\beamer@lefttext%
\else%
  \usebeamercolor{normal text}%
  \llap{\usebeamertemplate***{navigation symbols}\hskip0.1cm}%
  \vskip2pt%
\fi%
\hskip8pt
\includegraphics[height=1cm,keepaspectratio]{example-logo}~%
\vskip2pt
}
\makeatother
\logo{\includegraphics[height=0.7cm,keepaspectratio]{example-logo}}

\begin{document} 

\section{Section1}

\frame{Test Frame 1}

\section{Section 2}
\subsection{Subsection1 is a very long-titled subsection}
\subsection{Subsection2 is a very long-titled subsection}
\subsection{Subsection3 is a very long-titled subsection}
\subsection{Subsection4 is a very long-titled subsection}
\subsection{Subsection5 is a very long-titled subsection}
\subsection{Subsection6 is a very long-titled subsection}
\subsection{Subsection7 is a very long-titled subsection}
\subsection{Subsection8 is a very long-titled subsection}
\subsection{Subsection9 is a very long-titled subsection}
\frame{test Frame 2}
\end{document}

如下图所示，虽然在第一帧中左下角的徽标显示得很好，但在第二帧中，徽标的一部分超出了框架。我希望当这种情况发生时，徽标不会显示出来。

Answer 1

以下是使用蒂克兹测量图片的高度，并且只有在有足够空间时才插入它：

代码

\documentclass{beamer}
\usepackage{tikz}
\usepackage{xifthen}
\usetheme[hideothersubsections]{PaloAlto} 
\usecolortheme{seahorse}
\setbeamercovered{transparent}

\newcommand{\insertpic}[2][scale=1]% [options], picname
{   \begin{tikzpicture}[remember picture,overlay]
        \path (navenddummy);
        \pgfgetlastxy{\xnav}{\ynav}
        \vphantom{\hphantom{
            \node[inner sep=0pt,above right] (pictopdummy) {\includegraphics[#1]{#2}};
        }}
        \path (pictopdummy.north);
        \pgfgetlastxy{\xpic}{\ypic}
        \pgfmathtruncatemacro{\picornot}{\ypic < \ynav ? 1 : 0}
        \ifthenelse{\picornot=1}
            {\node[inner sep=0pt,above right] {\includegraphics[#1]{#2}};}
            {}
        %\node[inner sep=1pt,circle,fill=red] at (navenddummy) {};
        %\node[inner sep=1pt,circle,fill=blue] at (pictopdummy.north) {};
    \end{tikzpicture}
}

\makeatletter
\setbeamertemplate{sidebar \beamer@sidebarside}
{
\beamer@tempdim=\beamer@sidebarwidth%
\advance\beamer@tempdim by -6pt%
{\usebeamerfont{title in sidebar}%
  \vskip1.5em%
  \hskip3pt%
  \usebeamercolor[fg]{title in sidebar}%
  \insertshorttitle[width=\beamer@tempdim,center,respectlinebreaks]\par%
  \vskip1.25em%
}%
{%
  \hskip3pt%
  \usebeamercolor[fg]{author in sidebar}%
  \usebeamerfont{author in sidebar}%
  \insertshortauthor[width=\beamer@tempdim,center,respectlinebreaks]\par%
  \vskip1.25em%
}%
\insertverticalnavigation{\beamer@sidebarwidth}%
%=================
\begin{tikzpicture}[overlay,remember picture]
    \coordinate (navenddummy);
\end{tikzpicture}
%=================
\vfill
\ifx\beamer@sidebarside\beamer@lefttext%
\else%
  \usebeamercolor{normal text}%
  \llap{\usebeamertemplate***{navigation symbols}\hskip0.1cm}%
  \vskip2pt%
\fi%
\hskip8pt
%=================
\insertpic[height=0.7cm,keepaspectratio]{book.png}~
%=================
\vskip2pt
}
\makeatother
\logo{\includegraphics[height=0.7cm,keepaspectratio]{book.png}}

\begin{document} 

\section{Section1}

\frame{Test Frame 1}
\frame{test Frame 2}

\section{Section 2}
\subsection{Subsection1 is a very long-titled subsection}
\subsection{Subsection2 is a very long-titled subsection}
\subsection{Subsection3 is a very long-titled subsection}
\subsection{Subsection4 is a very long-titled subsection}
\subsection{Subsection5 is a very long-titled subsection}
\subsection{Subsection6 is a very long-titled subsection}
\subsection{Subsection7 is a very long-titled subsection}
\subsection{Subsection8 is a very long-titled subsection}
\subsection{Subsection9 is a very long-titled subsection}

\frame{test Frame 3}
\frame{test Frame 4}
\end{document}

输出