Footnotes with breakable tcolorbox

footnotestcolorbox

I am trying to just have one global system of footnotes (numbered) but I seem to have some issues with breakable tcolorboxes. Many of the answers I've read seem too advanced for my simple requirement of a single, global footnote system.

My preamble is

\documentclass[a4paper,10pt,titlepage]{article}
\usepackage[utf8]{inputenc}
\newcommand{\myparagraph}[1]{\paragraph{#1}\mbox{}\\}
\usepackage[a4paper,margin=3.5cm]{geometry} %Sets the page geometry
\usepackage{url}
\usepackage{dirtytalk}
\usepackage{graphicx} % Package for \includegraphics
\usepackage{wrapfig} % Figure wrapping
\usepackage[T1]{fontenc} % Output font encoding for international characters
\setlength{\parskip}{1em} % Set space when paragraphs are used
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{amsthm}
\usepackage{mathtools}
\usepackage{hyperref}
\usepackage{mathrsfs}
\usepackage{mdframed}
\usepackage[breakable]{tcolorbox}
\usepackage[justification=centering]{caption}
\usepackage{soul}

% Note that we enforce things so that everything is numbered off of theorems
\theoremstyle{definition} % to avoid italicizing theorems
\newmdtheoremenv{theo}{Theorem}
\newtheorem{thm}{Theorem}[section] % reset theorem numbering for each chapter
\newtheorem{defn}[thm]{Definition} % definition numbers are dependent on theorem numbers
\newtheorem{rmk}[thm]{Remark}
\newtheorem{exmp}[thm]{Example} % same for example numbers
\newtheorem{crlry}[thm]{Corollary}
\newtheorem{lemma}[thm]{Lemma}
\newtheorem{problem}{Problem}[section]

%% HOW TO KEEP FOOTNOTES GLOBAL
\usepackage{footnote}
\usepackage{etoolbox}
\BeforeBeginEnvironment{tcolorbox}{\savenotes}
\AfterEndEnvironment{tcolorbox}{\spewnotes}
\usepackage{blindtext}

\usepackage{geometry}
    %\usepackage{showframe} %This line can be used to clearly show the new margins

\newgeometry{vmargin={25mm}, hmargin={22mm,22mm}}

% Lets you use \blankpage to make a blank page
\newcommand{\blankpage}{
\newpage
\thispagestyle{empty}
\mbox{}
\newpage
}

An example of my footnoting is seen here:

\begin{tcolorbox}[breakable]
\begin{defn}[Equivalence class]
    Given an equivalence relation $\equiv$ defined on a set $S$, we define the equivalence class corresponding to any $a \in S$ as the set\footnote{If the equivalence relation in question is understood from context we'll sometimes just write $[a]$.}
    $$[a]_\equiv = \{ b \in S | a \equiv B \}$$
\end{defn}
\end{tcolorbox}

An example of my problem is seen in the picture below (note the two tcolorboxes, each beginning with footnote "a"). Anything I do outside the tcolorboxes has no problem though and is global and increments correctly.

enter image description here

Any help would be greatly appreciated, thank you!

Best Answer

Note that this combines both \BeforeBeginEnvironment and \renewenvironment. It has to do with executing commands before or after the optional argument.

\documentclass[a4paper,10pt,titlepage]{article}
\usepackage[utf8]{inputenc}
\newcommand{\myparagraph}[1]{\paragraph{#1}\mbox{}\\}
\usepackage[a4paper,margin=3.5cm]{geometry} %Sets the page geometry
\geometry{vmargin={25mm}, hmargin={22mm,22mm}}

\usepackage{url}
%\usepackage{dirtytalk}
\usepackage{graphicx} % Package for \includegraphics
\usepackage{wrapfig} % Figure wrapping
\usepackage[T1]{fontenc} % Output font encoding for international characters
\setlength{\parskip}{1em} % Set space when paragraphs are used
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{amsthm}
\usepackage{mathtools}
\usepackage{mathrsfs}
\usepackage{mdframed}
\usepackage[justification=centering]{caption}
\usepackage{soul}

% Note that we enforce things so that everything is numbered off of theorems
\theoremstyle{definition} % to avoid italicizing theorems
\newmdtheoremenv{theo}{Theorem}
\newtheorem{thm}{Theorem}[section] % reset theorem numbering for each chapter
\newtheorem{defn}[thm]{Definition} % definition numbers are dependent on theorem numbers
\newtheorem{rmk}[thm]{Remark}
\newtheorem{exmp}[thm]{Example} % same for example numbers
\newtheorem{crlry}[thm]{Corollary}
\newtheorem{lemma}[thm]{Lemma}
\newtheorem{problem}{Problem}[section]

%% HOW TO KEEP FOOTNOTES GLOBAL
\usepackage[breakable]{tcolorbox}
\usepackage{footnote}
\BeforeBeginEnvironment{tcolorbox}{\savenotes}
\AfterEndEnvironment{tcolorbox}{\spewnotes}
\makeatletter
\let\oldtcolorbox=\tcolorbox
\let\endoldtcolorbox=\endtcolorbox
\renewenvironment{tcolorbox}[1][]{\oldtcolorbox[#1]%
  \def\@mpfn{footnote}%
  \def\thempfn{\thefootnote}}%
{\endoldtcolorbox}
\makeatother

\usepackage{hyperref}

% Lets you use \blankpage to make a blank page
\newcommand{\blankpage}{
\newpage
\thispagestyle{empty}
\mbox{}
\newpage
}
\begin{document}
Test\footnote{First}

\begin{tcolorbox}[breakable]
\begin{defn}[Equivalence class]
    Given an equivalence relation $\equiv$ defined on a set $S$, we define the equivalence class corresponding to any $a \in S$ as the set\footnote{If the equivalence relation in question is understood from context we'll sometimes just write $[a]$.}
    $$[a]_\equiv = \{ b \in S | a \equiv B \}$$
\end{defn}
\end{tcolorbox}
\end{document}
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