%D \module
%D   [       file=page-mis,
%D        version=2008.11.17, % was part of page-flt.tex / 2000.10.20
%D          title=\CONTEXT\ Page Macros,
%D       subtitle=Postponing,
%D         author=Hans Hagen,
%D           date=\currentdate,
%D      copyright={PRAGMA ADE \& \CONTEXT\ Development Team}]
%C
%C This module is part of the \CONTEXT\ macro||package and is
%C therefore copyrighted by \PRAGMA. See mreadme.pdf for
%C details.

\writestatus{loading}{ConTeXt Page Macros / Postponing}

\registerctxluafile{page-pst}{1.001}

\unprotect

% postponing

\newevery\everytopofpage\relax

\appendtoks
    \the\everytopofpage
\to \everystarttext

\appendtoks
    \global\everytopofpage\emptytoks
\to \everystoptext

% \startpostponing [pagenumber] [+pageoffset]
%
% \startpostponing[2]
%   PAGE 2 \blank
% \stoppostponing
%
% \startpostponing[+1]
%   PAGE +1 \blank
% \stoppostponing
%
% \startpostponing[+2]
%   PAGE +2 \blank
% \stoppostponing
%
% \starttext \dorecurse{4}{\input tufte \page} \stoptext

%D There is no real need to use \LUA\ here but the bookkeeping
%D is somewhat easier and we also can erase buffers easier when
%D we keep a local cache, especially as we can flush per page.

%newif      \ifinpostponing                    % prevents nesting

\newcount      \c_page_postponed_blocks_next_page % set at the lua end
\newconditional\c_page_postponed_busy

\unexpanded\setvalue{\e!start\v!postponing}%
  {\bgroup
   \obeylines
   \doifnextoptionalelse{\egroup\page_postponed_blocks_start}{\egroup\page_postponed_blocks_start[0]}}

\unexpanded\setvalue{\e!stop\v!postponing}%
  {\ctxcommand{registerpostponedblock("\currentpostponedpage")}\relax}

\def\page_postponed_blocks_start[#1]%
  {\edef\currentpostponedpage{#1}%
   \grabbufferdatadirect{postponedblock}{\e!start\v!postponing}{\e!stop\v!postponing}}

% officially we should flush again after a flush as there can be new future pages
% but that will be looked into when we run into it

\unexpanded\def\page_postponed_blocks_flush_indeed
  {\begingroup
   \setsystemmode\v!postponing
   \settrue\c_page_postponed_busy
   \pagetotal\zeropoint        % here? still needed? (was after flush pagefloats)
   \the\everytopofpage\relax
  %\flushrestfloats
   \page_floats_flush_page_floats
   \setnormalcatcodes                 % postponing in verbatim
   \restoreglobalbodyfont             % otherwise problems inside split verbatim
   \ctxcommand{flushpostponedblocks()}%
   \relax
   \page_otr_command_flush_floats     % new but potential dangerous, maybe we need a classification
   \endgroup}                         % of blocks: with and without flush

\unexpanded\def\page_postponed_blocks_flush
  {\ifconditional\c_page_postponed_busy
     % probably a nested flush
   \else\ifnum\c_page_postponed_blocks_next_page=\zerocount
     % nothing in cache
   \else\ifnum\c_page_postponed_blocks_next_page<\zerocount
     % generic cache
     \page_postponed_blocks_flush_indeed
   \else\ifnum\c_page_postponed_blocks_next_page>\realpageno
     % future content
   \else
     % pending content
     \page_postponed_blocks_flush_indeed
   \fi\fi\fi\fi}

\protect \endinput
