%% pause.sty                                            25 May 99
%%---------------------------------------------------------------
%% This is a quick hack to enable repeated pages with incremental
%% contents e.g. for displaying slides uncovering step by step.
%%
%% The initial version (numbered 1.0) was written 07 May 99.
%% Version 1.1 was created 25 May 99 and fixed a naming problem.
%%
%% Possible extensions:
%% - make the page numbering optional (maybe using subnumbering)
%% - make action optional (for printed versions)
%%
%% Plan of attack (should work with TeX and LaTeX):
%% - Get some ressources, i.e. one counter, one token register and one
%%   box.
%% - When activated save the current page count in the counter and the
%%   output routine in the token register.
%% - Setup a new output routine, which saves away a copy of the
%%   current page.
%% - Trigger this output routine to save the cumulated page contents.
%% - Restore the former output routine and run it with the restored
%%   saved contents.
%% - Reset the page count and reinsert the contents once again,
%%   removing the last glue item on the page.
%%
%%
%% Please send suggestions for improvement or (even better) patches to
%%   Klaus Guntermann      guntermann@iti.informatik.tu-darmstadt.de
%%
\newbox\p@uses@vebox
\newtoks\p@uses@veoutput
\newcount\p@uses@vepage
\def\pause{\global\p@uses@vepage=\count0\relax % save pagenumber
  \p@uses@veoutput=\output % make backup copy of output routine
  \output={\global\setbox\p@uses@vebox=\box255}% copy current
      % contents only, when triggered
  \vfill\eject % trigger now
  \output=\p@uses@veoutput % restore output routine
  \unvcopy\p@uses@vebox % insert contents
  \eject % now really show the output
  \global\count0=\p@uses@vepage\relax %restore page number
  \unvbox\p@uses@vebox\vskip-\lastskip % and insert again for next turn
}