%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% Module: ZzTeX Blocks
%
% Synopsis: This module provides facilities for defining and creating
% element blocks.
%
% Author: Paul C. Anagnostopoulos
% Created: 23 August 1989
%
% Copyright 1989--2020 by Paul C. Anagnostopoulos
% under The MIT License (opensource.org/licenses/MIT)
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Block Definition
% ----- ----------
\setlist \zblocklist = {}
\def \defineblock #1#2#3#4{% {\name}{\endname}{snap?}{redefine}
\if \emptyargp{#4}%
\withname\definecount{#1depth}{0}%
\withname\definecount{#1number}{0}%
\withname\definetoks{#1comptext}%
\withname\gdef{#1varinit}{}%
\if #3\withname\declaresnapitem{#1number}\fi
\append{#1}{\zblocklist}%
\fi}
\def \resetinvcontext #1{% {\name}
\zdeclareeveryvcontext{\zblockvcontext{#1}}}
\def \zblockvcontext #1{% {\name}
\zsavevcontext{\name{#1depth}=\the\name{#1depth}%
\name{#1number}=\the\name{#1number}%
\name{#1comptext}={\the\name{#1comptext}}}%
\global\name{#1depth}= 0\relax
\global\name{#1number}= 0\relax}
% Block Utilities
% ----- ---------
\defineskip{\enclosingbaselineskip}{0pt}
\defineskip{\enclosingleftss}{0pt}
\definedimen{\enclosingparindent}{0pt}
\definedimen{\enclosingparrag}{0pt}
\defineskip{\enclosingparskip}{0pt}
\defineskip{\enclosingrightss}{0pt}
\def \beginblockscope #1{%
\begingroup
\zpushblock{#1}%
\enclosingbaselineskip = \baselineskip
\enclosingleftss = \leftskip
\tdimena = \leftskip
\advance \enclosingleftss by -\tdimena
\enclosingparindent = \parindent
\enclosingparrag = \parrag
\enclosingparskip = \parskip
\enclosingrightss = \rightskip
\tdimena = \rightskip
\advance \enclosingrightss by -\tdimena}
\def \endblockscope #1{%
\zpopblock{#1}%
\endgroup}
\def \processdesign #1#2{% {\block}{type etc.}
\zprocessvariant{#1}%
\resetnumber = {}%
\if \definedp{#1#2design}%
\name{#1#2design}\relax % \relax terminates numbers and such.
\else
\error{nodesign}{No design has been defined for the `\string#1#2' block}%
\fi
\zprocesswith
{\globaldefs = 1 \the\resetnumber}}
\def \inblockp #1{% {\block-name}
\if \posp{\name{#1depth}}\true \else \false \fi}
\def \setcomptext #1{% {\xxxcomptext}
\edef \znext {\comptextformat}%
#1= \expandafter{\znext}}%
\def \blockmustbein #1#2{% {\inner}{\outer}
\if \zerop{\name{#2depth}}%
\error{blkmustnest}{A `\string#1' must be nested in a `\string#2'}%
\fi}
\def \blockcantbein #1#2{% {\inner}{\outer}
\if \posp{\name{#2depth}}%
\error{blkcantnest}
{A `\string#1' cannot be nested inside a `\string#2'}%
\fi}
\def \closeifinblock #1#2{% {\block}{\endblock}
\if \inblockp{#1}#2\fi}
% Block Stack
% ----- -----
\setlist \zblockstack = {}
\setlist \zlinestack = {}
\def \zpushblock #1{%
\push{#1}{\zblockstack}%
\edef \znext {\noexpand\push{\the\inputlineno}}%
\znext{\zlinestack}}
\def \zpopblock #1{%
\pop{\zblk}{\zblockstack}%
\pop{\zline}{\zlinestack}%
\stringeql{\znext}{\zblk}{#1}%
\if \notp{\znext}%
\error{blkinvnest}{The `\string\end#1' command does not match the
`\zblk' block that was started on line \zline}%
\fi}
\def \zemptyblockstackp {\emptylistp{\zblockstack}}
% Block Variants
% ----- --------
\def \definevariant #1#2#3{% {\block}{\style}{\modifier0,\modifier1,...}
\if \emptyargp{#3}%
\error{varmod}{Between 1 and 8 modifier commands must be specified}%
\fi
\withname\definecount{#2variant}{0}%
\withname\xdef{#1varinit}{\name{#1varinit}\name{#2variant}=0}%
{\tcounta = 0
\zdefvarpre #2#3,\zmark
\if \gtrp{\tcounta}{8}%
\error{varmod}{Between 1 and 8 modifier commands must be specified}%
\fi
\ztoksa = \expandaftertwice{\name{\zvarcase\lcromannumeral\tcounta}}%
\edef \znext {\global\let \name{#2varcase}=\the\ztoksa}%
\znext}}
\def \zdefvarpre #1#2,#3\zmark{% \style\modifier,\modifier,...,\zmark
\xdef #2{\noexpand\variant{\name{#1variant}=\the\tcounta}}%
\increment \tcounta
\if \notp{\emptyargp{#3}}\zdefvarpre #1#3\zmark \fi}
\gdef \zvariant {} % Holds \stylevariant assignments.
\def \variant #1{% {\stylevariant assignment}
{\ztoksa = \expandafter{\zvariant}%
\ztoksb = {#1}%
\xdef \zvariant {\the\ztoksa \the\ztoksb}}%
\ignorespaces}
\def \zprocessvariant #1{% {\block}
\name{#1varinit}%
\zvariant \relax % \relax terminates numbers and such.
\gdef \zvariant {}}
\def \varcase #1{% \style
\name{#1varcase}#1}
\long\def \zvarcasei #1#2{% \style {var1 code}
\ifcase \name{#1variant}#2\else\zbadvar\fi\relax}
\long\def \zvarcaseii #1#2#3{% \style {var1 code}{var2 code}
\ifcase \name{#1variant}#2\or#3\else\zbadvar\fi\relax}
\long\def \zvarcaseiii #1#2#3#4{%
\ifcase \name{#1variant}#2\or#3\or#4\else\zbadvar\fi\relax}
\long\def \zvarcaseiv #1#2#3#4#5{%
\ifcase \name{#1variant}#2\or#3\or#4\or#5\else\zbadvar\fi\relax}
\long\def \zvarcasev #1#2#3#4#5#6{%
\ifcase \name{#1variant}#2\or#3\or#4\or#5\or#6\else\zbadvar\fi\relax}
\long\def \zvarcasevi #1#2#3#4#5#6#7{%
\ifcase \name{#1variant}#2\or#3\or#4\or#5\or#6\or#7\else\zbadvar\fi\relax}
\long\def \zvarcasevii #1#2#3#4#5#6#7#8{%
\ifcase \name{#1variant}#2\or#3\or#4\or#5\or#6\or#7\or#8\else\zbadvar\fi\relax}
\long\def \zvarcaseviii #1#2#3#4#5#6#7#8#9{%
\ifcase\name{#1variant}#2\or#3\or#4\or#5\or#6\or#7\or#8\or#9\else\zbadvar\fi\relax}
\def \setvariant #1{% \modifier
#1%
\zvariant \relax
\gdef \zvariant {}}
\def \zbadvar {%
\zzerror{Invalid value for variant}}
% Block Options
% ----- -------
\gdef \zwith {} % Holds \with parameters.
%~ The |\with| modifier can be used to modify specific design
%~ parameters for the following block. It only makes sense
%~ preceding block commands. Sometimes it is used with parameters
%~ that are specifically intended for |\with|:
%~ \with{\itemnumber=4} \list{number}
%~ Other times it is used with a parameter that needs to be
%~ changed for one particular block.
%~ \with{\advance\belowskip by -8pt} \float{figure}
%~ Again, be careful to use |\with| only on block commands.
\long\def \with #1{% {parameter-assignments} %^modifier
{\ztoksa = \expandafter{\zwith}%
\ztoksb = {#1}%
\xdef \zwith {\the\ztoksa \the\ztoksb}}%
\ignorespaces}
\def \zprocesswith {%
\zwith \relax % \relax terminates numbers and such.
\gdef \zwith {}}
%~ This block modifier forces a page break above the block.
\def \breakabove {% %^modifier
\with{\abovepenalty=\breakalways}}
%~ This block modifier forces a page break below the block.
\def \breakbelow {% %^modifier
\with{\belowpenalty=\breakalways}}
% Common Design Parameters
% ------ ------ ----------
% These design parameters are used by a variety of ZZTeX's blocks, so
% they are defined here.
% Integer parameters:
\definecount{\abovepenalty}{0} % Penalty above block.
\definecount{\authorlevel}{0} % Author ToC entry level.
\definecount{\belowpenalty}{0} % Penalty below block.
\definecount{\continue}{0} % Block is continued (bit 0) and/or continuation (bit 1).
\definecount{\difficulty}{0} % Level of difficulty of the block.
% Flag parameters:
\setflag \allowbreaks = \false % Allow page breaks in block?
\setflag \allowintoc = \false % Allow section in ToC?
% Dimension parameters:
\definedimen{\height}{0pt} % Height of text.
\definedimen{\ruleshift}{0pt} % Horizontal shift for rule.
\definedimen{\ruleheight}{0pt} % Height (thickness) of rule.
\definedimen{\rulewidth}{0pt} % Width of rule.
\definedimen{\topadjust}{\mindimen} % Adjustment for head at top of page.
\definedimen{\vshift}{0pt} % Vertical shift.
\definedimen{\width}{0pt} % Width of text.
% Skip (glue) parameters:
\defineskip{\aboveskip}{0pt} % Base/base skip above block.
\defineskip{\belowskip}{0pt} % Base/base skip below block.
\defineskip{\columngutter}{0pt} % Width of gutter between columns.
\defineskip{\interrowskip}{0pt} % Extra space between rows.
\defineskip{\leftindent}{0pt} % Left indentation glue.
\defineskip{\numbersink}{0pt} % Sinkage to section number, or
\defineskip{\numberskip}{0pt} % Space b/b to section number.
\defineskip{\parhang}{0pt} % Hanging indent for paragraph.
\defineskip{\rightindent}{0pt} % Right indentation glue.
\defineskip{\ruleskip}{0pt} % Vskip for rule.
\defineskip{\textsink}{0pt} % Vsink for text.
\defineskip{\textskip}{0pt} % Base/base skip for text.
\defineskip{\titlesink}{0pt} % Sinkage to section title, or
\defineskip{\titleskip}{0pt} % Space b/b to section title.
% Token list parameters:
\definetoks{\authortext} % Part/chapter author text.
\definetoks{\bodyfont} % Font for body of block.
\definetoks{\divisions} % List of division names.
\definetoks{\numberfont} % Font for block number.
\definetoks{\numberwordfont} % Font for block word like "chapter".
\definetoks{\openertext} % Part/chapter opener text.
\definetoks{\position} % Position of the block.
\definetoks{\resetnumber} % List of sequence numbers to reset.
\definetoks{\rulecolor} % Color of a rule.
\definetoks{\runners} % Running head/foot macros.
\definetoks{\style} % Heading style.
\definetoks{\textcolor} % Color of text.
\definetoks{\titlefont} % Font for title.
% Macro parameters:
\def \numberformat #1{} % {code} %~ Formatter for block number.
\def \paging {} % {code} %~ Page control commands.
\def \providemark #1{} % {code} %~ Provide marks for the block.
\def \titleformat {} % {code} %~ Formatter for title.
% The \continue Parameter
% --- --------- ---------
% The \continue parameter is set as follows:
% 0: neither continued nor continuation
% 1: continued
% 2: continuation
% 3: both continuation and continued
\def \continuedp {\oddp{\continue}}
\def \continuationp {\gtrp{\continue}{1}}
\def \zsetcontinue {%
\if \andp{\zerop{\continue}}{\continuation}%
\continue = 2\relax
\fi}
% Break Element
% ----- -------
\long\def \breakelement #1{%
\global\setflag \zinpar = {\hmodep}%
\if \zinpar \flushendpar \fi
#1%
\if \zinpar \noindent \ignorespaces \fi}