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%D \module
%D [ file=pack-bck, % moved from pack-rul,
%D version=20111115, % 1998.10.16,
%D title=\CONTEXT\ Packaging Macros,
%D subtitle=Simple Backgrounds,
%D author=Hans Hagen \& Wolfgang Schuster,
%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 Packaging Macros / Simple Backgrounds}
%D The code here is already pretty old and is used for simple
%D backgrounds. As it is still used WS adapted the code to the
%D new command handler methods so that it gets a second life. So
%D it made sense to mkvi ir as well. Some more code is moved here
%D too.
%D \macros
%D {setupbackground,startbackground,background}
%D
%D The section deals with backgrounds in the running text. This
%D means that texts is to be collected and split over pages. To
%D show what can be done, we provide this part of the
%D documentation with some gray background and a red frame.
%D Both the background and frame can have all characteristics
%D of \type{\framed}.
%D
%D \starttyping
%D \setupbackground
%D [backgroundoffset=4pt,
%D background=screen,
%D frame=on,
%D framecolor=red,
%D leftoffset=2pt]
%D \stoptyping
%D
%D The implementation is not that sophisticated, but suffices.
%D The main problem with this kind of functionality is to get
%D the spacing all right.
%D
%D Specifying the background is more or less the same as
%D specifying a framed box.
%D
%D \showsetup{setupbackground}
%D
%D {\em This mechanism is sort of obsolete and textbackgrounds should
%D be used instead.}
\unprotect
\installcorenamespace {background}
\installframedcommandhandler \??background {background} \??background
% The mode is not that public an dmostlu an initial mode:
%
% 0 : no split
% 1 : no split, honoring leftskip (messy)
% 2 : split
% 3 : split, honoring leftskip (messy)
%
% While processing the modes will change from 3->1 or 2->0. Don't
% depend on the mode being public currently as it could become a
% key.
\setnewconstant\backgroundsplitmode\plusthree
\appendtoks
\setuevalue{\e!start\currentbackground}{\background_start [\currentbackground]}%
\setuevalue{\e!stop \currentbackground}{\background_stop }%
\setuevalue {\currentbackground}{\background_direct[\currentbackground]}%
\to \everydefinebackground
\unexpanded\def\background_start[#tag]%
{\endgraf
\begingroup
\def\currentbackground{#tag}%
\doifelse{\backgroundparameter\c!state}\v!start
{\dosingleempty\background_start_indeed}
{\dosingleempty\background_start_ignore}}
\def\background_start_indeed[#settings]%
{\setupcurrentbackground[#settings,\c!state=\v!start,\c!offset=\v!overlay]%
\let\background_stop\background_stop_indeed
\setbox0\vbox\bgroup
\vbox to \lineheight{}\vskip\zeropoint
\blank[\v!disable]
\leftskip \backgroundparameter\c!leftoffset
\rightskip\backgroundparameter\c!rightoffset}
\def\background_start_ignore[#settings]%
{\let\background_stop\background_stop_ignore}
\let\background_stop\relax
\unexpanded\def\background_stop_indeed
{\endgraf
\removelastskip
\egroup
\dimen2\leftskip % new **
\forgetall
\ifinsidefloat
\backgroundsplitmode\zerocount
\fi
\ifcase\backgroundsplitmode
\inheritedbackgroundframed{\box0}%
\or
\hskip\dimen2
\inheritedbackgroundframed{\box0}%
\else
\splitmaxdepth\boxmaxdepth
\splittopskip\topskip
\setbox2\vsplit0 to \lineheight % get rid of fake line
\doloop
{\ifdim\pagetotal=\zeropoint % empty page
\scratchdimen\textheight
\backgroundsplitmode\plusone % split to max height
\else
\setbox2\vbox{\backgroundparameter\c!before}%
\scratchdimen\dimexpr\pagegoal-\ht2-\pagetotal\relax
\backgroundsplitmode\plustwo % split to partial height
\fi
\advance\scratchdimen\dimexpr-\backgroundparameter\c!topoffset-\backgroundparameter\c!bottomoffset\relax
\ifdim\scratchdimen>2\lineheight\relax % reasonable, will be configurable
\ifdim\ht0>\scratchdimen % larger than page
\setbox2\vsplit0 to \scratchdimen
\else
\setbox2\box0
\backgroundsplitmode\zerocount % no split
\fi
\setbox2\vbox \ifcase\backgroundsplitmode\or to \textheight \fi % max split
{\vskip\backgroundparameter\c!topoffset
\unvcopy2
\prevdepth\dp2
\obeydepth
\vskip\backgroundparameter\c!bottomoffset
\vfill}
\backgroundparameter\c!before
\ifcase\backgroundsplitmode\or\or % partial split
\ifdim\pagegoal<\maxdimen
\pagegoal=1.2\pagegoal % be a bit more tolerant
\fi
\fi
\startlinecorrection
\ifnum\backgroundsplitmode=\plusthree
\hskip\dimen2 % new **
\fi
\inheritedbackgroundframed{\box2}%
\stoplinecorrection
\ifcase\backgroundsplitmode % no split
\backgroundparameter\c!after
\else % some split
\page_otr_fill_and_eject_page % no \page !
\fi
\else
\page
\fi
\ifdim\ht0>\zeropoint \else
\exitloop
\fi}%
\fi
\endgroup
\endgraf}
\unexpanded\def\background_stop_ignore
{\endgroup
\endgraf}
\unexpanded\def\background_direct[#tag]%
{\begingroup
\def\currentbackground{#tag}%
\doifelse{\backgroundparameter\c!state}\c!start
\background_direct_indeed
\background_direct_ignore}
\def\background_direct_indeed
{\dowithnextboxcs\background_direct_finish\vbox}
\def\background_direct_finish
{\setupcurrentbackground[\c!offset=\v!overlay]%
\inheritedbackgroundframed{\flushnextbox}%
\endgroup}
\def\background_direct_ignore
{\endgroup}
\definebackground[\v!background]
\ifdefined\startbackground \else
\expandafter\let\startbackground\csname\e!start\v!background\endcsname
\expandafter\let\stopbackground \csname\e!stop \v!background\endcsname
\expandafter\let\background \csname \v!background\endcsname
\fi
\setupbackground
[\c!leftoffset=.5\bodyfontsize,
\c!rightoffset=\backgroundparameter\c!leftoffset,
\c!topoffset=\!!zeropoint,
\c!bottomoffset=\backgroundparameter\c!topoffset,
\c!state=\v!start,
\c!radius=.5\bodyfontsize,
\c!corner=\v!rectangular,
\c!frame=\v!off,
\c!color=,
\c!depth=\!!zeropoint,
\c!background=\v!screen,
\c!backgroundcolor=\backgroundparameter\c!color,
\c!screen=\@@rsscreen,
\c!before=,
\c!after=]
%D \startbuffer
%D \setupbackground[state=start,frame=on]
%D
%D \startbackground
%D \input ward
%D \stopbackground
%D
%D \background{\input ward\par}
%D
%D \setupbackground[state=stop]
%D
%D \startbackground
%D \input ward
%D \stopbackground
%D
%D \background{\input ward\par}
%D \stopbuffer
%D
%D \typebuffer \getbuffer
%D \macros
%D {backgroundline}
%D
%D For the moment an undocumented feature, but a candidate
%D for going public.
\unexpanded\def\backgroundline[#color]%
{\dontleavehmode
\dowithnextbox{\background_add_to_nextbox{#color}}\hbox}
\unexpanded\def\background_add_to_nextbox#color% handy helper
{\hbox
{\dousecolorparameter{#color}%
\vrule
\!!width \nextboxwd
\!!height\nextboxht
\!!depth \nextboxdp
\hskip-\nextboxwd
\flushnextbox}}
\protect \endinput
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