[Tex/LaTex] Create custom note environment with tcolorbox

environmentsparagraphstcolorbox

I just stumbled upon the tcolorbox package but can't seem to find my way through its extensive manual.

What I'm trying to achieve is to create a custom environment to add short notes into a body of text. The enclosed paragraph should start with the word 'Note:' in bold and appear next to a vertical line flush with the left margin of the surrounding text, like so:

So far, I've been using the mdframed package for this but I am starting to get annoyed by its frequent warnings of the sort

You got a bad break because the last box will be empty you have to
change it manually by changing the text, the space or something else.

Here's the code I've been using so far.

\documentclass[11pt]{scrartcl}

\usepackage[framemethod=tikz]{mdframed}
\newmdenv[
    topline=false,
    bottomline=false,
    rightline=false,
    innerrightmargin=0pt
]{siderule}
\newenvironment{note}%
    {\begin{siderule}\textbf{Note:}}
    {\end{siderule}}

\usepackage{blindtext}

\begin{document}

\blindtext
\begin{note}
    Here comes a useful note for demonstration. Let's add enough text to break the line, just to be sure the vertical line extends with the text.
\end{note}
\blindtext

\end{document}

I hope someone can help streamline it and make it more robust with tcolorbox.

Best Answer

Such a box is quite easy with the borderline options, which draw vertical bars (or other stuff)

Since the note environment should be versatile, there might be an optional argument that sets other options if needed, see the second (ugly!) example of the note environment.

The vertical etc. spacings before/after and inside of the box might be change using left=... etc. and before skip={} etc. keys.

\documentclass[11pt]{article}

\usepackage[most]{tcolorbox}

\newtcolorbox{note}[1][]{%
  enhanced jigsaw, % better frame drawing
  borderline west={2pt}{0pt}{red}, % straight vertical line at the left edge
  sharp corners, % No rounded corners
  boxrule=0pt, % no real frame,
  fonttitle={\large\bfseries},
  coltitle={black},  % Black colour for title
  title={Note:\ },  % Fixed title
  attach title to upper, % Move the title into the box
  #1
}

\usepackage{blindtext}

\begin{document}

\blindtext
\begin{note}
    Here comes a useful note for demonstration. Let's add enough text to break the line, just to be sure the vertical line extends with the text.
\end{note}

\begin{note}[borderline west={2pt}{0pt}{blue}, colback=yellow, drop shadow={red,opacity=0.6}]
    Here comes a useful note for demonstration. Let's add enough text to break the line, just to be sure the vertical line extends with the text.
\end{note}

\blindtext

\end{document}

For more sophisticated usages of borderline etc. please have a look on Reproduce a PDF table with colored vertical semi lines

Here's a version in which the first line of the note box is aligned with the label of an enumerate environment:

\documentclass[11pt]{scrartcl}

\usepackage{enumitem}
\usepackage[most]{tcolorbox}


\makeatletter
\newtcolorbox{note}[1][]{%
  enhanced jigsaw, % better frame drawing
  borderline west={1pt}{0pt}{black}, % straigh vertical line at the left edge
  sharp corners, % No rounded corners
  boxrule=0pt, % no real frame,
  fonttitle={\large\bfseries},
  coltitle={black},  % Black colour for title
  title={Note:\ },  % Fixed title
  attach title to upper, % Move the title into the box,
  right=0pt,
  top=0pt,
  bottom=0pt,
  frame hidden,
  baseline={\tcb@height-2\kvtcb@boxsep+\baselineskip-2\lineskip}, %%%% Needs more to be done for other setups
  #1
}
\makeatother

\usepackage{blindtext}

\begin{document}

\blindtext
\begin{note}
    Here comes a useful note for demonstration. Let's add enough text to break the line, just to be sure the vertical line extends with the text.
\end{note}

\begin{enumerate}
\item \begin{note}
    Here comes a useful note for demonstration. Let's add enough text to break the line, just to be sure the vertical line extends with the text.
\end{note}

\item \begin{note}
    Here comes a useful note for demonstration. Let's add enough text to break the line, just to be sure the vertical line extends with the text.
\end{note}

\end{enumerate}



\blindtext

\end{document}

Related Solutions

[Tex/LaTex] Define custom environment

The \ifthenelse condition ends prematurely and leaves an open environment hanging around in the middle of nowhere.

In conjunction with tcolorbox environment, the end - delimiter is \endtcolorbox and I suggest to use two \ifthenelse statements, one for the start code of the environment and another one for the end code.

A better approach would use \DeclareTColorbox, in my opinion or a weird \scantokens construct.

Also possible: Use \tcolorboxenvironment to wrap around an existing solution environment.

\documentclass{article}

\usepackage{ifthen}

\usepackage[most]{tcolorbox}

\newboolean{solution}

\newenvironment{solution}{%
  \ifthenelse{\boolean{solution}}{%
    \tcolorbox[breakable, width=\textwidth, colframe=red, colback=white]
    }{%
  }%
}{\ifthenelse{\boolean{solution}}{\endtcolorbox}{}}


\begin{document}

\setboolean{solution}{true}
\begin{solution}
  \begin{align*}
    x^2 + y^2 &= z^2\\
    \Rightarrow x &= \sqrt{z^2 - y^2}\\
    &= ...
  \end{align*}
\end{solution}

\setboolean{solution}{false}
\begin{solution}
  \begin{align*}
    x^2 + y^2 &= z^2\\
    \Rightarrow x &= \sqrt{z^2 - y^2}\\
    &= ...
  \end{align*}
\end{solution}


\end{document}

Cleaner solution with two different environments

\documentclass{article}

\usepackage[most]{tcolorbox}


\tcbset{
  commonboxes/.style={nobeforeafter},
  nobox/.style={commonboxes,blank,breakable},
  solutionbox/.style={commonboxes,breakable, colframe=red, colback=white}
}


\newtcolorbox{solutionbox}[1][]{
  solutionbox,#1
}

\newtcolorbox{solutionbox*}[1][]{%
  nobox,#1
}






\begin{document}

\begin{solutionbox*}
  \begin{align*}
    x^2 + y^2 &= z^2\\
    \Rightarrow x &= \sqrt{z^2 - y^2}\\
    &= ...
  \end{align*}
\end{solutionbox*}

\begin{solutionbox}
  \begin{align*}
    x^2 + y^2 &= z^2\\
    \Rightarrow x &= \sqrt{z^2 - y^2}\\
    &= ...
  \end{align*}
\end{solutionbox}



\end{document}

Third installment of a solution with \NewEnviron and the \BODY command.

\documentclass{article}


\usepackage{environ}
\usepackage{ifthen}
\usepackage[shortlabels]{enumitem}
\usepackage{amssymb}
\usepackage{mathtools}
\usepackage[most]{tcolorbox}

\newboolean{solution}

\tcbset{
 commonboxes/.style={nobeforeafter,breakable},
  nobox/.style={commonboxes,blank,breakable},
  solutionbox/.style={commonboxes,breakable, colframe=red, colback=white}
}


\NewEnviron{solution}[1][]{%
  \ifthenelse{\boolean{solution}}{%
    \tcolorbox[solutionbox, width=\textwidth,#1]
    \BODY
    }{%
  }%
}[\ifthenelse{\boolean{solution}}{\endtcolorbox}{}]





\begin{document}

\begin{enumerate}[label={\alph*)}]
\item Compute the Fourier transform of $e^{-|x|}$ for $x\in \mathbb{R}$.
  \begin{solution}[colframe=blue]
    \begin{align*}
      \hat{f}(\xi)&=\frac{1}{\sqrt{2\pi}}\int_{-\infty}^{\infty}e^{-|x|}e^{-ix\xi}dx\\
      &=\frac{1}{\sqrt{2\pi}}\int_{0}^{\infty}e^{-x-ix\xi}dx+\int_{-\infty}^0e^{x-ix\xi}dx\\
      &=\frac{1}{\sqrt{2\pi}}\int_{0}^{\infty}(e^{-x-ix\xi}-e^{-x+ix\xi})dx\\
      &=\frac{1}{\sqrt{2\pi}}[\frac{1}{-(1+i\xi)}(-1)-\frac{1}{-1+i\xi}(-1)]\\
      &=\frac{1}{\sqrt{2\pi}}[\frac{1-i\xi}{1+\xi^2}+\frac{-(1+i\xi)}{1+\xi^2}]\\
      &=\frac{1}{\sqrt{2\pi}}\frac{-2i\xi}{1+\xi^2}\\
      &=-\sqrt{\frac{2}{\pi}}\frac{i\xi}{1+\xi^2}
    \end{align*}
  \end{solution}             
\item Compute the Fourier transform of $e^{-a|x|^2},~a>0$, directly, where $x\in \mathbb{R}$.\\
  \begin{solution}
    \begin{align*}
      \hat{f}(\xi)&=\frac{1}{\sqrt{2\pi}}\int_{-\infty}^{\infty}e^{-a|x|^2}e^{-ix\xi}dx\\
      &=\frac{1}{\sqrt{2\pi}}\int_{-\infty}^{\infty}e^{-a(x+\frac{i\xi}{2a})^2+\frac{-\xi^2}{4a}}dx~~~~~~~~x'\doteq x+\frac{i\xi}{2a}\\
      &=\frac{1}{\sqrt{2\pi}}e^{-\frac{\xi^2}{4a}}\int_{-\infty}^{\infty}e^{-ax^2}dx\\
      &=\frac{e^{-\frac{\xi^2}{4a}}}{2a}
    \end{align*}
  \end{solution}

\end{enumerate}

\setboolean{solution}{true}

\begin{enumerate}[label={\alph*)}]
\item Compute the Fourier transform of $e^{-|x|}$ for $x\in \mathbb{R}$.
  \begin{solution}[colframe=blue]
    \begin{align*}
      \hat{f}(\xi)&=\frac{1}{\sqrt{2\pi}}\int_{-\infty}^{\infty}e^{-|x|}e^{-ix\xi}dx\\
      &=\frac{1}{\sqrt{2\pi}}\int_{0}^{\infty}e^{-x-ix\xi}dx+\int_{-\infty}^0e^{x-ix\xi}dx\\
      &=\frac{1}{\sqrt{2\pi}}\int_{0}^{\infty}(e^{-x-ix\xi}-e^{-x+ix\xi})dx\\
      &=\frac{1}{\sqrt{2\pi}}[\frac{1}{-(1+i\xi)}(-1)-\frac{1}{-1+i\xi}(-1)]\\
      &=\frac{1}{\sqrt{2\pi}}[\frac{1-i\xi}{1+\xi^2}+\frac{-(1+i\xi)}{1+\xi^2}]\\
      &=\frac{1}{\sqrt{2\pi}}\frac{-2i\xi}{1+\xi^2}\\
      &=-\sqrt{\frac{2}{\pi}}\frac{i\xi}{1+\xi^2}
    \end{align*}
  \end{solution}             
\item Compute the Fourier transform of $e^{-a|x|^2},~a>0$, directly, where $x\in \mathbb{R}$.\\
  \begin{solution}
    \begin{align*}
      \hat{f}(\xi)&=\frac{1}{\sqrt{2\pi}}\int_{-\infty}^{\infty}e^{-a|x|^2}e^{-ix\xi}dx\\
      &=\frac{1}{\sqrt{2\pi}}\int_{-\infty}^{\infty}e^{-a(x+\frac{i\xi}{2a})^2+\frac{-\xi^2}{4a}}dx~~~~~~~~x'\doteq x+\frac{i\xi}{2a}\\
      &=\frac{1}{\sqrt{2\pi}}e^{-\frac{\xi^2}{4a}}\int_{-\infty}^{\infty}e^{-ax^2}dx\\
      &=\frac{e^{-\frac{\xi^2}{4a}}}{2a}
    \end{align*}
  \end{solution}

\end{enumerate}

\end{document}

The \BODY command contains the environment 'text' and is printed only in the case solution is true.

Custom environment for tcolorbox not working with certain option

When starting an environment foo by writing \begin{foo} a couple of things happen; among these, the current environment's name is stored in the macro \@currenvir, and then the macro \foo is expanded. That's the reason why when defining wrappers for environments it's always a good idea to use the internal macros \foo and \endfoo: in this way you (usually) get clearer error messages.

However, tcolorbox does things differently, and the macro \tcolorbox (more exactly, some other macro a couple of expansions later) also sets \@currenvir:

\documentclass[twocolumn]{article}% twocol for smaller snapshot

\usepackage{tcolorbox}

\begin{document}

\csname@currenvir\endcsname
\begin{center}
\csname@currenvir\endcsname
\end{center}
\csname@currenvir\endcsname
\begin{tcolorbox}
\csname@currenvir\endcsname
\end{tcolorbox}

\end{document}

I don't quite know the rationale behind this choice, but I guess that's (also) why a tcolorbox version of \newenvironment is provided, namely \newtcolorbox:

\documentclass{article}

\usepackage{tcolorbox}
\tcbuselibrary{theorems}

\newtcolorbox{myenv}{ams align}

\begin{document}

\begin{myenv}
a &= b & c&= d \\
e &= f
\end{myenv}

\end{document}

Best Answer

Related Solutions

[Tex/LaTex] Define custom environment

Custom environment for tcolorbox not working with certain option

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