Code inside an equation environment is executed 4 times (or isn't it?).

Question

I created a small example:

\documentclass[a4paper,12pt]{article}
\usepackage{amsmath}
\usepackage[pdfstartview=FitH]{hyperref}
\usepackage{bookmark}
\begin{document}
one line
\newcounter{test}
\[\text{\stepcounter{test}\bookmark[dest=whatever]{my equation}one equation}\]
counter value: \arabic{test}.
\end{document}

It creates 4 bookmarks but increases the counter only by 1. How is that (even logically) possible? Either this equation environment somehow executes the code 4 times (maybe first measuring the contents or whatever), then the counter should be increased by four. Or it only executes once, then there should only be one bookmark.

How do I get it to display only one bookmark? (moving it out of the equation is not an option since this happens inside a macro which at the same time marks the equation as target.)

update:

alright, egregs \tbookmark command fixed my minimal example. turns out it was too minimal. here is another one which went back to not working:

\documentclass[a4paper,12pt]{article}
\usepackage{amsmath}
\usepackage[pdfstartview=FitH]{hyperref}
\usepackage[atend]{bookmark}
\makeatletter\newcommand{\tbookmark}[2][]{\iffirstchoice@\bookmark[#1]{#2}\fi}\makeatother
\newcounter{nops}
\newcommand{\nop}{\stepcounter{nops}\raisebox{\ht\strutbox}{\hypertarget{nop\arabic{nops}}{}}\begingroup\edef\x{\endgroup\noexpand\BookmarkAtEnd{\noexpand\tbookmark[dest=nop\arabic{nops}]{page \arabic{nops}}}}\x}
\begin{document}
one line
\[\text{\nop one equation}\]
counter value: \arabic{nops}.
\end{document}

Answer 1

\text uses internally \mathchoice (so jfbu was right), but amstext.sty redefines \stepcounter and \addtocounter in such a way that they act only once.

A cheap solution would be to define a special \bookmark command:

\makeatletter
\newcommand{\tbookmark}[2][]{%
  \iffirstchoice@
    \bookmark[#1]{#2}%
  \fi}
\makeatother

that will be free of the problem. Probably something that Heiko should take care of.

One might try also with letltxmacro (the redefinition must go after \usepackage{bookmark}):

\usepackage{letltxmacro}
\makeatletter
\LetLtxMacro{\orig@bookmark}{\bookmark}
\renewcommand{\bookmark}[2][]{%
  \iffirstchoice@\orig@bookmark[#1]{#2}\fi}
\makeatother

--- Added after Peter's edits ---

Any command to be used inside \text and which sets bookmarks or hypertargets should be defined in terms of \iffirstchoice@:

\newcommand{\nop}{%
  \stepcounter{nops}%
  \iffirstchoice@
    \raisebox{\ht\strutbox}{\hypertarget{nop\arabic{nops}}{}}
  \fi}

The AMS packages define \text using the conditional \iffirstchoice@; essentially, \text{...} is defined to become

\mathchoice{\firstchoice@true\textrm{...}}
           {\firstchoice@false\textrm{...}}
           {\firstchoice@false\textrm{...}}
           {\firstchoice@false\textrm{...}}

One has to remember that \mathchoice typesets all four forms and TeX chooses one depending on the needed math style; with \iffirstchoice@<tokens>\fi we are sure that the <tokens> are found only once.