%D \module
%D   [      file=s-pre-60,
%D        version=2004.03.15,
%D          title=\CONTEXT\ Style File,
%D       subtitle=Presentation Environment 60,
%D         author=Hans Hagen,
%D           date=\currentdate,
%D      copyright={PRAGMA / Hans Hagen \& Ton Otten}]
%C
%C This module is part of the \CONTEXT\ macro||package and is
%C therefore copyrighted by \PRAGMA. See mreadme.pdf for
%C details.

\startmode[paper]
    \let\StartSteps\relax
    \let\StopSteps \relax
    \let\FlushStep \relax
    \let\ResetStep \relax
    \let\StartBusy\relax
    \let\StopBusy \relax
    \endinput
\stopmode

\newcounter\StepCounter
\newcounter\StepMaximum

\useJSscripts[stp]

\startsetups[set-stepper]

    \ifnum\getvariable{stepper}{nofsteps}>\StepMaximum

        \dostepwiserecurse {\numexpr(\StepMaximum+1)} {\getvariable{stepper}{nofsteps}} {1}
          {\doifnotmode{nosteps,nostep}
             {\expanded{\defineproperty[step:\recurselevel][layer][state=stop,global=yes]}}}

        \xdef\StepMaximum{\getvariable{stepper}{nofsteps}}

    \fi

\stopsetups

\setvariables
  [stepper]
  [set=\setups{set-stepper},
   nofsteps=50]

\defineproperty[step:busy][layer][state=start,global=no]

\definereference [SetupStepper]  [JS(SetupStepper{step,\StepMaximum})]
\definereference [ResetStepper]  [JS(ResetStepper)]
\definereference [CheckStepper]  [JS(CheckStepper{\StepCounter})]
\definereference [InvokeStepper] [JS(InvokeStepper)]

\def\ResetStep {\doglobal\newcounter\StepCounter}
\def\NextStep  {\doglobal\increment \StepCounter}
\def\PrevStep  {\doglobal\decrement \StepCounter}

% todo: roll back blank

\def\StepLayer     {step:\StepCounter}
\def\NextStepLayer {step:\the\numexpr\StepCounter+1\relax}
\def\FirstStepLayer{step:1}

\startmode[mkiv]

    \def\StartStep
      {\startproperty[\StepLayer]%
       \ignorespaces}

    \def\StopStep
      {\removeunwantedspaces
       \stopproperty}

\stopmode

\startnotmode[mkiv]

    \def\StartStep
      {\ifvmode
         \scratchskip\lastskip
         \vskip-\scratchskip
         \startproperty[\StepLayer]%
         \vskip\scratchskip
       \else
         \startproperty[\StepLayer]%
       \fi
       \ignorespaces}

    \def\StopStep
      {\removeunwantedspaces
       \stopproperty}

\stopnotmode

\def\StartSteps{\iftrialtypesetting\else\ResetStep\NextStep\StartStep\fi}
\def\StopSteps {\iftrialtypesetting\else\StopStep \PrevStep          \fi}
\def\FlushStep {\iftrialtypesetting\else\StopStep \NextStep\StartStep\fi}

\appendtoks
  \ResetStep
\to \everyaftershipout

\def\StartBusy{\startproperty[step:busy]\ignorespaces}
\def\StopBusy {\removeunwantedspaces\stopproperty}

\setupinteraction
  [%openaction=SetupStepper,
   closeaction=ResetStepper,
   openpageaction=CheckStepper,
   closepageaction=ResetStepper]

\defineoverlay[invoke][\overlaybutton{InvokeStepper}]

\setupbackgrounds
  [text]
  [background=invoke]

% bonus

\useMPlibrary[nav]

\definepalet
  [navplus]
  [attach=interactioncolor,
   comment=interactioncolor]

\setupcomment
  [symbol={comment-normal,comment-down},
   textlayer=\StepLayer,
   option=buffer,
   height=\textheight,
   width=\textwidth,
   margin=0pt]

\setupattachments
  [symbol={attach-normal,attach-down},
   textlayer=\StepLayer]

%D Handy:

\def\StartLocalSteps{\ResetStep}
\def\StopLocalSteps {}

\def\StartLocalStep {\NextStep\StartStep}
\def\StopLocalStep  {\StopStep}

%D used as (given some definitions):
%D
%D \starttyping
%D \StartLocalSteps
%D     \startcombination[both]
%D         {\StartLocalStep\placestreamlayer[left]\StopLocalStep}  {}
%D         {\StartLocalStep\placestreamlayer[right]\StopLocalStep} {}
%D     \stopcombination
%D \StopLocalSteps
%D \stoptyping

\endinput
