I would like to change the symbol for the end of proofs (the square) used in Beamer. It is quite thin, not very visible in some colorthemes. How can I have a thicker border and still in the structure color?
[Tex/LaTex] How to customise (e.g. make thicker) the end-proof symbol in Beamer
beamersymbolstheorems
Related Solutions
If you are using the proof environment, then I am afraid that there's no automatic way to break the text (allowframebreaks won't work here, since we're dealing with a block).
You can define an environment that behaves as proof, but without using the end-mark; you then can use this new environment for the first frames of the proof and then, use the standard proof environment for the last frame; here's an example of the definition of such environment (which I called proofs) and its ussage:
\documentclass{beamer}
\usetheme{Warsaw}
\usepackage{lipsum}
\makeatletter
\newenvironment<>{proofs}[1][\proofname]{%
\par
\def\insertproofname{#1\@addpunct{.}}%
\usebeamertemplate{proof begin}#2}
{\usebeamertemplate{proof end}}
\makeatother
\begin{document}
\begin{frame}
\begin{proofs}
\lipsum[1]
\end{proofs}
\end{frame}
\begin{frame}
\begin{proofs}[\proofname\ (Cont.)]
\lipsum[1]
\end{proofs}
\end{frame}
\begin{frame}
\begin{proof}[\proofname\ (Cont.)]
\lipsum[1]
\end{proof}
\end{frame}
\end{document}
As requested in a comment, I have defined now three new environments: proofs, which uses a block with title given by \insertproofname (default "Proof") and suppresses the end-mark; proofc, which suppresses both the title and the end-mark, and proofe which suppresses the title but adds the end-mark; the first environment is to be used to start the proof, the second one, to continue the proof, and the third one, to end the proof:
\documentclass{beamer}
\usetheme{Warsaw}
\usepackage{lipsum}
\makeatletter
\newenvironment<>{proofs}[1][\proofname]{%
\par
\def\insertproofname{#1\@addpunct{.}}%
\usebeamertemplate{proof begin}#2}
{\usebeamertemplate{proof end}}
\newenvironment<>{proofc}{%
\setbeamertemplate{proof begin}{\begin{block}{}}
\par
\usebeamertemplate{proof begin}}
{\usebeamertemplate{proof end}}
\newenvironment<>{proofe}{%
\par
\pushQED{\qed}
\setbeamertemplate{proof begin}{\begin{block}{}}
\usebeamertemplate{proof begin}}
{\popQED\usebeamertemplate{proof end}}
\makeatother
\begin{document}
\begin{frame}
\begin{proofs}
\lipsum[1]
\end{proofs}
\end{frame}
\begin{frame}
\begin{proofc}
\lipsum[1]
\end{proofc}
\end{frame}
\begin{frame}
\begin{proofe}
\lipsum[1]
\end{proofe}
\end{frame}
\end{document}
It's difficult to provide precise advise without a minimal working example; however, the following code reproduces the problem mentioned:
\documentclass{beamer}
\usetheme{CambridgeUS}
\usepackage{lipsum}
\setbeamertemplate{navigation symbols}{}
\begin{document}
\begin{frame}
\begin{proof}
\lipsum[4]
\end{proof}
\begin{proof}
\lipsum[4]
\end{proof}
\end{frame}
\end{document}
the output shows that the qed symbol for the last proof environment almost disappears from the frame:
Adding a convenient \vskip just before \end{proof} solves the problem:
\documentclass{beamer}
\usetheme{CambridgeUS}
\usepackage{lipsum}
\setbeamertemplate{navigation symbols}{}
\begin{document}
\begin{frame}
\begin{proof}
\lipsum[4]
\end{proof}
\begin{proof}
\lipsum[4]\vskip-1\baselineskip
\end{proof}
\end{frame}
\end{document}
One has to be careful about the length used for the \vskip; a value larger than \baselineskip will produce undesired results.
As a personal note, you should reconsider using frames containing too much text (sometimes it's unavoidable, but give it a second thought).
Best Answer
Beamer defines the
end-proofsymbol in this way:therefore it is possible to change it by means of something like:
Defining a new symbol with TikZ:
it becomes:
Complete example:
Result:
Notice that in order to maintain the
structurecolor of the current theme, the command usesstructure.fg.