setting up a command switching between \flushleft and \flushright environments

Question

I'm trying to make code formatting a conversation between two ends with boxes left and right respectively. So far i have seen examples in which two \NewEnviron were used respectively for left side boxes and right ones.

I'd like to make a single \newcommand that will decide on the basis of a parameter value whether it should be \begin{flushleft} or \begin{flushright}

here is my non-working try:

\documentclass{article}
\usepackage{tcolorbox}}
\usepackage{ifthen}
\usepackage{varwidth}

\newcommand{\bubble}[3]{%
  \ifthenelse{\equal{#1}{\flushright}}{\begin{\flushright}}{\begin{\flushleft}}
    \begin{tcolorbox}[width=0.5\textwidth, title=#2]
       #3
    \end{tcolorbox}
  \ifthenelse{\equal{#1}{\flushright}}{\end{\flushright}}{\end{\flushleft}}

% use it like this:
\bubble{flushleft}{friend}{hello, what's your plan today?}
\bubble{flushright}{me}{nothing!}

Answer 1

If you give the first parameter to \bubbles without backslash, you can just use it as parameter to \begin. This simplifies the command a lot, with no test being necessary.

I suppose varwidth is to be used somewhere else, because for this simple example it isn't necessary.

\documentclass{article}
\usepackage{tcolorbox}
\usepackage{varwidth}
\usepackage{lipsum}

\newcommand{\bubbles}[3]{%
  \begin{#1}
    \begin{tcolorbox}[width=0.5\textwidth, title=#2]
       #3
    \end{tcolorbox}
  \end{#1}
}

\begin{document}

Test

\bubbles{flushleft}{Title Left}{Contents left\\\lipsum[1][1-2]}

\bubbles{flushright}{Title Right}{Contents right\\\lipsum[1][3-4]}

More text

\end{document}

Answer 2

You can achieve a much simpler syntax:

\documentclass{article}
\usepackage[many]{tcolorbox}

\newcommand{\bubble}[3]{%
  \begin{flushleft}
  \if>#1\hspace*{\fill}\fi
  \mbox{\begin{tcolorbox}[width=0.5\textwidth, title=#2]
    #3
  \end{tcolorbox}}%
  \end{flushleft}
}

\begin{document}

\bubble{<}{friend}{hello, what's your plan today?}
\bubble{>}{me}{nothing!}

\end{document}

Answer 3

If you want to use the same title and alignment for each speaker, it might be a better idea to store that information inside a key you can use as the first mandatory argument to \bubble. I added an optional argument to \bubble with which individual customizations can be made.

The following does so using expkv-def for a key=value interface (of course other packages could be used for this as well).

The box key can be used to forward additional keys to the tcolorbox environment (in the example I use this to specify colours for each speaker).

The align key might take the value center in which case a center environment is used, else the used environment will be flush<align>, so right and left are possible values.

\documentclass[]{article}

\usepackage{tcolorbox}
\usepackage{expkv-def}

\makeatletter
% we define new keys here. The `store' type of keys will store the value during
% its usage inside the macros. The `code' type allows own definitions. We use it
% to define a key that will add additional contents to an existing macro
% (\bubble@box) with a comma between the old and new material.
% With `initial' we set initial values for the keys `width` and `align`, all
% other macros are initially empty (title and box).
% The `BOX' key will overwrite any other option passed to `tcolorbox', whereas
% the `box' key will add to the list of options.
\ekvdefinekeys{bubbles}
  {
     store title = \bubble@title
    ,store align = \bubble@align
    ,store BOX   = \bubble@box
    ,code  box   = \edef\bubble@box{\unexpanded\expandafter{\bubble@box,#1}}
    ,store width = \bubble@wd
    ,initial width = .5\textwidth
    ,initial align = left
  }
% we define a shorthand macro to set options of bubbles.
\ekvsetdef\bubbleoptions{bubbles}
% the real macro
\newcommand\bubble[3][]
  {%
    % contain the definitions done by the key=value interface inside a group so
    % that one call can't affect another one.
    \begingroup
      % test if the macro holding defaults exists, if so call it 
      \ifcsname bubble@defaults@\detokenize{#2}\endcsname
        \csname bubble@defaults@\detokenize{#2}\endcsname
      \fi
      % parse the additional options with our key=value interface
      \bubbleoptions{#1}%
      % handle the `center' alignment by comparing the current alignment with a
      % temporary macro
      \def\bubble@tmp{center}%
      \begin{\ifx\bubble@tmp\bubble@align\else flush\fi\bubble@align}
        % expand the contents of `\bubble@box' so that the key=value interface
        % of tcolorbox can do its job
        \expandafter\bubble@startbox\expandafter{\bubble@box}%
          #3%
        \end{tcolorbox}%
      \end{\ifx\bubble@tmp\bubble@align\else flush\fi\bubble@align}
    \endgroup
  }
% helper macro to expand the contents of `\bubble@box' before calling
% `tcolorbox'.
\newcommand\bubble@startbox[1]
  {%
    % check if the title is empty, if so, don't use the title key of tcolorbox.
    \ifx\bubble@title\@empty
      \begin{tcolorbox}[width=\bubble@wd, #1]
    \else
      \begin{tcolorbox}[width=\bubble@wd, title=\bubble@title, #1]
    \fi
  }
% define a default option list. The optional argument is used as is for the
% `tcolorbox' options, the rest is parsed by our key=value interface. Since we
% use it inside of `\edef' the values passed to the keys here are fully
% expanded. This shouldn't be an issue normally.
\newcommand\bubbledef[3][]
  {%
    \expandafter\edef\csname bubble@defaults@\detokenize{#2}\endcsname
      {\unexpanded{\def\bubble@box{#1}}\bubbleoptions{#3}}%
  }
\makeatother

% define the two speakers (with short name A and B)
\bubbledef[colframe=red!50!black]{A}{title=Speaker A, align=left}
\bubbledef[colframe=green!50!black]{B}{title=Speaker B, align=right}

\usepackage{duckuments} % just for some dummy text

\begin{document}
\bubble{A}{\blindduck[-]}
\bubble{B}{\blindduck[-]}
\bubble[title=New Speaker]{}{A new speaker shows up.}
\bubble[align=center, width=.7\textwidth]{}{Another fat speaker is here.}
\end{document}

---

Changes:

2021-02-23, 18:38 (UTC+1)

• added a lot of comments
• added an optional argument to \bubbledef to set the default tcolorbox options in an, imho, nicer way.
• changed the box key to add additional options instead of clearing the list
• added the BOX key (does what the box key did previously)