%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% Module:    ZzTeX New Running Head/Foot Scheme
%
% Synopsis:  The new running head/foot scheme is an improvement over the
%            original scheme.
%
% Author:    Paul C. Anagnostopoulos
% Created:   26 November 1997
%
% Copyright 1989--2020 by Paul C. Anagnostopoulos
% under The MIT License (opensource.org/licenses/MIT)
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%                       Data Structures
%                       ---- ----------


\def \zdefrun {normal}

\setlist \zrunlist = {}

\setflag \zoverrun = \false

\def \zcurback   {%
  \if \definedp \backgroundnormalformat \backgroundnormalformat \fi}
\def \zcurheader {\headernormalformat}
\def \zcurfooter {\footernormalformat}

%                       Specify Runners
%                       ------- -------


%~ This command discards any current runner styles and sets up to use style
%~ *style1* on the current page, *style2* on the next, *style3* on the one after
%~ that, and so forth. The last style specified is used as the style for all
%~ subsequent pages (it becomes the default style). No spaces are allowed in the
%~ list.

\def \setrunners #1{%                                   {style1,style2,style3,...} %^runners
  {\if \zoverrun \pop{\zoverstyle}{\zrunlist}\fi
   \commalist{\zrunlist}{#1}%
   \maplist{\gdef \zdefrun {##1}}{\zrunlist}%
   \if \zoverrun \expandafter\overriderunners\expandafter{\zoverstyle}\fi
   \zsetcurrun}}

%~ This command overrides the style for the current page, using style *style*
%~ instead. After the current page, runner styles revert to those established
%~ by the last |\setrunners| command.

\def \overriderunners #1{%                              {style} %^runners
  \if \notp{\emptylistp{\zrunlist}}%
    \pop{\znext}{\zrunlist}%
  \fi
  \push{#1}{\zrunlist}%
  \global\setflag \zoverrun = \true
  \zsetcurrun}

%~ This command is simply a shorthand for |\overriderunners{blind}|.

\def \blindrunners {%                                   %^runners
  \overriderunners{blind}}

%                       Internal Common Macros
%                       -------- ------ ------


\def \zsetrunnerstoks #1{%                              {\token-reg}
  \expandafter\setrunners\expandafter{\the#1}}

\def \zoverriderunnerstoks #1{%                         {\token-reg}
  \expandafter\overriderunners\expandafter{\the#1}}

\def \zoldrunners #1{}

%                       Output Routine Interface
%                       ------ ------- ---------


\def \zsetcurrun {%
  \if \emptylistp{\zrunlist}%
    \edef \znext {\zdefrun}%
  \else
    \listtop{\znext}{\zrunlist}%
  \fi
  \ztoksa = \expandaftertwice{\name{\background\znext format}}%
  \xdef \zcurback {%
    \noexpand\if \noexpand\definedp\the\ztoksa \the\ztoksa \noexpand\fi}%
  \ztoksa = \expandaftertwice{\name{\header\znext format}}%
  \xdef \zcurheader {\the\ztoksa}%
  \ztoksa = \expandaftertwice{\name{\footer\znext format}}%
  \xdef \zcurfooter {\the\ztoksa}}

\def \znextpagerunners {%
   \if \notp{\emptylistp{\zrunlist}}\pop{\znext}{\zrunlist}\fi
   \zsetcurrun
   \global\setflag \zoverrun = \false}