thmboxes_white.sty

% inspired by
% https://texblog.org/2015/09/30/fancy-boxes-for-theorem-lemma-and-proof-with-mdframed/
% https://tex.stackexchange.com/questions/391443/new-theorem-environment-with-manual-theorem-number

% notation: 

% types: thm (theorem) / def (definition) / xmp (examples) / rem (remark)
% \begin{thm}[Name]{Label}{Reference Number}

% \end{thm}


% ============= %
%    THEOREM    %
% ============= %

% new counter (idk what this does ngl but it's needed)
\newcounter{thm}[section]\setcounter{thm}{0}

% set up new environment theorem with 3 arguments
\newenvironment{thm}[3][]{%
% newcommand thethm outputs argument 3 (Theorem Number)
\renewcommand{\thethm}{#3}
% step counter for reference(?)
\refstepcounter{thm}%
% Set up bounding boxes in tikz
% if there is no argument 1 (Title), then box
\ifstrempty{#1}%
    {\mdfsetup{%
    frametitle={%
    \tikz[baseline=(current bounding box.east),outer sep=0pt]
    \node[anchor=east,rectangle,fill=blue!20]
    {\strut Theorem~\thethm};}}
    }%
% if there is argument 1 (Title), then add title
{\mdfsetup{%
frametitle={%
\tikz[baseline=(current bounding box.east),outer sep=0pt]
\node[anchor=east,rectangle,fill=blue!20]
{\strut Theorem~\thethm:~#1};}}%
}%
% set bounds of box
\mdfsetup{innertopmargin=5pt,linecolor=blue!20,%
linewidth=2pt,topline=true,%
frametitleaboveskip=\dimexpr-\ht\strutbox\relax
}
% start environment with label as argument 2
\begin{mdframed}[]\relax%
\label{#2}}{\end{mdframed}}

% ================ %
%    DEFINITION    %
% ================ %

% new counter (idk what this does ngl but it's needed)
\newcounter{dfn}[section]\setcounter{dfn}{0}
% set up new environment theorem with 3 arguments
\newenvironment{dfn}[3][]{%
% newcommand thedef outputs argument 3 (Theorem Number)
\renewcommand{\thedfn}{#3}
% step counter for reference(?)
\refstepcounter{dfn}%
% Set up bounding boxes in tikz
% if there is no argument 1 (Title), then box
\ifstrempty{#1}%
    {\mdfsetup{%
    frametitle={%
    \tikz[baseline=(current bounding box.east),outer sep=0pt]
    \node[anchor=east,rectangle,fill=green!20]
    {\strut Definition~\thedfn};}}
    }%
% if there is argument 1 (Title), then add title
{\mdfsetup{%
frametitle={%
\tikz[baseline=(current bounding box.east),outer sep=0pt]
\node[anchor=east,rectangle,fill=green!20]
{\strut Definition~\thedfn:~#1};}}%
}%
% set bounds of box
\mdfsetup{innertopmargin=5pt,linecolor=green!20,%
linewidth=2pt,topline=true,%
frametitleaboveskip=\dimexpr-\ht\strutbox\relax
}
% start environment with label as argument 2
\begin{mdframed}[]\relax%
\label{#2}}{\end{mdframed}}

% ============ %
%    REMARK    %
% ============ %

% new counter (idk what this does ngl but it's needed)
\newcounter{rem}[section]\setcounter{rem}{0}

% set up new environment theorem with 3 arguments
\newenvironment{rem}[3][]{%
% newcommand therem outputs argument 3 (Theorem Number)
\renewcommand{\therem}{#3}
% step counter for reference(?)
\refstepcounter{rem}%
% Set up bounding boxes in tikz
% if there is no argument 1 (Title), then box
\ifstrempty{#1}%
    {\mdfsetup{%
    frametitle={%
    \tikz[baseline=(current bounding box.east),outer sep=0pt]
    \node[anchor=east,rectangle,fill=purple!20]
    {\strut Remark~\therem};}}
    }%
% if there is argument 1 (Title), then add title
{\mdfsetup{%
frametitle={%
\tikz[baseline=(current bounding box.east),outer sep=0pt]
\node[anchor=east,rectangle,fill=purple!20]
{\strut Remark~\therem:~#1};}}%
}%
% set bounds of box
\mdfsetup{innertopmargin=5pt,linecolor=purple!20,%
linewidth=2pt,topline=true,%
frametitleaboveskip=\dimexpr-\ht\strutbox\relax
}
% start environment with label as argument 2
\begin{mdframed}[]\relax%
\label{#2}}{\end{mdframed}}

% ============= %
%    EXAMPLE    %
% ============= %

% new counter (idk what this does ngl but it's needed)
\newcounter{xmp}[section]\setcounter{rem}{0}

% set up new environment theorem with 3 arguments
\newenvironment{xmp}[3][]{%
% newcommand therem outputs argument 3 (Theorem Number)
\renewcommand{\thexmp}{#3}
% step counter for reference(?)
\refstepcounter{xmp}%
% Set up bounding boxes in tikz
% if there is no argument 1 (Title), then box
\ifstrempty{#1}%
    {\mdfsetup{%
    frametitle={%
    \tikz[baseline=(current bounding box.east),outer sep=0pt]
    \node[anchor=east,rectangle,fill=yellow!40]
    {\strut Example~\thexmp};}}
    }%
% if there is argument 1 (Title), then add title
{\mdfsetup{%
frametitle={%
\tikz[baseline=(current bounding box.east),outer sep=0pt]
\node[anchor=east,rectangle,fill=yellow!40]
{\strut Example~\thexmp:~#1};}}%
}%
% set bounds of box
\mdfsetup{innertopmargin=5pt,linecolor=yellow!40,%
linewidth=2pt,topline=true,%
frametitleaboveskip=\dimexpr-\ht\strutbox\relax
}
% start environment with label as argument 2
\begin{mdframed}[]\relax%
\label{#2}}{\end{mdframed}}