How to reference page and column in a two-column text

Question

Does it exist a command like pageref with which I can indicate the column too? (I am writing a two-column text and I would like to give an indication more precise than the simple page).

Answer 1

Detecting/tracking the (current) column is not easy. However, a somewhat simplistic yet effective way of identifying the column can be done by labelling the x-coordinate on the page. If that x-coordinate is less than half the page width, you should be within the left (first) column, otherwise you're in the right (second) column.

Here is that implementation using the savepos module from zref:

\documentclass[twocolumn]{article}
\usepackage{xcolor}
\usepackage[savepos]{zref}
\newcommand{\columnlabel}[1]{\label{#1}\zsaveposx{#1}}
\newcommand{\columnref}[1]{%
  \ifdim\zposx{#1}sp<.5\pdfpagewidth
    left% column 1
  \else
    right% column 2
  \fi
}
\usepackage{lipsum}
\begin{document}
\sloppy% Just for this example
\lipsum[1-5]
\textcolor{red}{\columnlabel{important}Some important text}%
\lipsum[6-10]
See \textcolor{red}{page~\pageref{important} (\columnref{important} column)}.
\end{document}

You could update \columnref to output something of the format <page>-<column> in the following way:

% Output <page>-<column> as a reference
\newcommand{\columnref}[1]{%
  \pageref{#1}-%
  \ifdim\zposx{#1}sp<.5\pdfpagewidth
    1% column 1
  \else
    2% column 2
  \fi
}