Combining content of marginnotes

Question

I use marginnotes (sometimes inside of mdframed environments) to write at the margin whenever a concept is defined, e.g.:

\documentclass{article}
\usepackage{marginnote,tikz,mdframed}
\usepackage{amsthm}

\newmdtheoremenv[linecolor=black]{definition}{Definition}

\newcommand{\defi}[1]{%
  \marginnote{\tiny #1}%
  \emph{#1}}

\begin{document}

\begin{definition}
An \defi{apple} is a fruit, a \defi{mirror} is an object 
and a \defi{fish} is an animal.
\end{definition}
\end{document}

Alas, I have a problem when two or more things are defined in the same line---in the example, "apple", "mirror" and "fish" overlap in the margin.

I am aware that this is a feature, but wonder whether it would be possible to combine the contents of both calls to marginnote.

(Replacing marginnote by marginpar gives me "Float(s) lost.")

Ideally, in the margin I would read "apple, mirror, fish"

I wonder if it is possible to change marginnote so that

• when a \marginnote is reached, its argument is appended to some list (of tokens?) ... ideally, adding some separator such as ,);
• when the marginnote is typeset, it resets this list of tokens to nothing

I am also aware of the advanced sidenotes features of memoir, but I have to stick with article.

---

As a last resort, if this is not possible, I am considering the following:

• every time \defi is called it appends to a comma-separated list of definitions;
• using something like everypage to then call a tikzpicture to overlay the list on the margin of the document and reset the list contents

---

Edit: @TeXnician pointed out a similar question at Margin note automatic concatenation, however David's answer there has the side effect of adding the notes inside the mdframed box. (And I did not manage to run Tobi's answer, but I'm guessing I might run into the same Float(s) lost problem.)

Answer 1

You could try something like this. It only checks if the definitions (their begin) are on the same line and the same page.

\documentclass{article}
\usepackage{marginnote}
\usepackage{zref-savepos,zref-abspage}
\usepackage{expl3}


\ExplSyntaxOn\makeatletter
\int_new:N \g_tassio_note_int
\seq_new:N\g_tassio_note_seq

\newcommand{\defi}[1]{%
  \int_gincr:N \g_tassio_note_int
  \bool_if:nTF
  {
   \int_compare_p:n 
    {
     \zposy{tassionotepos\int_eval:n{\g_tassio_note_int}} 
     =  
     \zposy{tassionotepos\int_eval:n{\g_tassio_note_int +1}}
    }
   &&
   \int_compare_p:n  
   {
    \zref@extractdefault { tassionotepage\int_eval:n{\g_tassio_note_int } }{abspage}{-1}
    =
    \zref@extractdefault { tassionotepage\int_eval:n{\g_tassio_note_int +1} }{abspage}{-1}
   }
  }
   {
    \seq_gput_left:Nn \g_tassio_note_seq {#1}
   }
   {
    \seq_gput_left:Nn \g_tassio_note_seq {#1}
    \marginnote{\tiny \seq_use:Nn \g_tassio_note_seq {,~}}%
    \seq_gclear:N \g_tassio_note_seq
   } 
  \zref@label {tassionotepage\int_use:N\g_tassio_note_int}\zsaveposy {tassionotepos\int_use:N\g_tassio_note_int}
  \emph{#1}}

\ExplSyntaxOff\makeatother

\begin{document}
An \defi{apple} is a fruit, a \defi{mirror} is an object
and a \defi{fish} is an animal.
\\ \defi{duck} 


\newpage \defi{snowmann}

\end{document}