From 85b7bc695629926641c7cb752fd478adfdf374f3 Mon Sep 17 00:00:00 2001
From: Marius <mariausol@gmail.com>
Date: Sun, 4 Jul 2010 15:32:09 +0300
Subject: stable 2010-05-24 13:10

---
 tex/context/base/pack-lyr.mkiv | 786 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 786 insertions(+)
 create mode 100644 tex/context/base/pack-lyr.mkiv

(limited to 'tex/context/base/pack-lyr.mkiv')

diff --git a/tex/context/base/pack-lyr.mkiv b/tex/context/base/pack-lyr.mkiv
new file mode 100644
index 000000000..0cb3ee244
--- /dev/null
+++ b/tex/context/base/pack-lyr.mkiv
@@ -0,0 +1,786 @@
+%D \module
+%D   [       file=pack-lyr,
+%D        version=2000.10.20,
+%D          title=\CONTEXT\ Packaging Macros,
+%D       subtitle=Layers,
+%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.
+
+\writestatus{loading}{ConTeXt Packaging Macros / Layers}
+
+% todo : first / last / next / +... => page key
+%        test on left/right box when no doublesided option given
+%        use \ifcsname instead of doifvalue
+
+\unprotect
+
+% When being backgrounds layers get the background offset
+% displacement. Should be an option, on by default
+% (compatibility).
+
+% positie=forceer == ja maar dan ook in status=herhaal
+
+%D The layering mechanism implemented here is independent of
+%D the output routine, but future extensions may depend on a
+%D more close cooperation.
+
+%D First we overload a macro from \type {core-rul}. From now on
+%D we accept a (optional) argument: the specific layer it
+%D will go in. This means that we can move an overlay from one
+%D background to the other using the dimensions of the parent.
+
+\ifx\undefined\defineoverlay \message{loaded to early} \wait \fi
+
+\unexpanded\def\defineoverlay
+  {\dotripleempty\dodefineoverlay}
+
+\def\dodefineoverlay[#1][#2][#3]% overlay [layer] content
+  {\ifthirdargument
+    %\writestatus{BEWARE}{This (overlay definition) has changed!}% temp
+     \def\docommand##1{\setvalue{\??ov##1}{\setlayer[#2]{\executedefinedoverlay{##1}{#3}}}}
+   \else
+     \def\docommand##1{\setvalue{\??ov##1}{\executedefinedoverlay{##1}{#2}}}%
+   \fi
+   \processcommalist[#1]\docommand}
+
+%D When tracing is turned on, a couple of boxes will
+%D show up as well as the reference point.
+
+\newif\iftracelayers % \tracelayerstrue
+
+%D This handy constant saved some string memory.
+
+\def\@@layerbox{@@layerbox}
+
+%D \macros
+%D   {definelayer}
+%D
+%D Each layer gets its own (global) box. This also means that
+%D the data that goes into a layer, is typeset immediately.
+%D Each layer automatically gets an associated overlay,
+%D which can be used in any background assignment.
+
+% todo : links/rechts
+
+\unexpanded\def\definelayer
+  {\dodoubleargument\dodefinelayer}
+
+\def\dodefinelayer[#1][#2]% \zeropoint ipv \!!zeropoint
+  {\setuplayer
+     [#1]
+     [\c!doublesided=,\c!preset=,
+      \c!state=\v!start,\c!direction=\v!normal,\c!option=,
+      \c!x=\zeropoint,\c!y=\zeropoint,\c!position=\v!no,
+      \c!line=0,\c!column=0,
+      \c!width=\nextboxwd,\c!height=\nextboxht,
+      \c!offset=\zeropoint,\c!rotation=, % geen 0 !
+      \c!hoffset=\zeropoint,\c!voffset=\zeropoint,
+      \c!dx=\zeropoint,\c!dy=\zeropoint,
+      \c!location=rb,\c!position=\v!no,\c!page=,
+      \c!method=\v!overlay,
+      \c!sx=1,\c!sy=1,\c!corner=,#2]%
+   \doifvalue{\??ll#1\c!doublesided}\v!yes
+     {\dopresetlayerbox{\v!left #1}%
+      \dopresetlayerbox{\v!right#1}}%
+   \dopresetlayerbox{#1}%
+   \defineoverlay[#1][\composedlayer{#1}]}
+
+\def\dopresetlayerbox#1%
+  {\ifcsname\@@layerbox#1\endcsname
+     \resetlayer[#1]%
+   \else
+     \expandafter\newbox\csname\@@layerbox#1\endcsname
+   \fi}
+
+%D \macros
+%D   {setuplayer}
+%D
+%D After a layer is defined, you can change its
+%D characteristics.
+
+\unexpanded\def\setuplayer
+  {\dodoubleargument\dosetuplayer}
+
+\def\dosetuplayer[#1][#2]%
+  {\def\docommand##1{\getparameters[\??ll##1][#2]}%
+   \processcommalist[#1]\docommand}
+
+%D \macros
+%D   {setlayer}
+%D
+%D Data is moved into a layer with the following macro. When
+%D \type {position} is set, relative positioning is used, with
+%D the current point as reference point. Otherwise the topleft
+%D corner is used as reference point.
+%D
+%D \starttyping
+%D \setlayer [identifier] [optional parameters] {data}
+%D \stoptyping
+
+\newcount\currentlayerdata
+
+\let\currentlayerwidth \!!zeropoint
+\let\currentlayerheight\!!zeropoint
+
+\def\setcurrentlayerdimensions
+  {\dodoubleempty\dosetcurrentlayerdimensions}
+
+\def\dosetcurrentlayerdimensions[#1][#2]% name left|right
+  {\edef\currentlayerwidth {\thelayerwidth {#2#1}}%
+   \edef\currentlayerheight{\thelayerheight{#2#1}}}
+
+\def\thelayerwidth #1{\the\wd\executeifdefined{\@@layerbox#1}\emptybox}
+\def\thelayerheight#1{\the\ht\executeifdefined{\@@layerbox#1}\emptybox}
+
+\def\setlayer
+  {\dotripleempty\dosetlayer}
+
+% \def\dosetlayer[#1][#2][#3]% #4 == box do \fi is ok
+%   {\doifelsevalue{\??ll#1\c!state}\v!stop
+%      {\dowithnextbox\donothing\hbox}
+%      {\ifthirdargument
+%         \dodosetlayer[#1][#2][#3]%
+%       \else
+%         \dodosetlayer[#1][][#2]%
+%       \fi}}
+
+\def\dosetlayer[#1][#2][#3]% #4 == box do \fi is ok
+  {\doifelsevalue{\??ll#1\c!state}\v!stop
+     {\dowithnextbox\donothing\hbox}
+     {\ifthirdargument
+        \dodosetlayer[#1][#2][#3]%
+      \else
+        \doifassignmentelse{#2}
+          {\dodosetlayer[#1][][#2]}%
+          {\dodosetlayer[#1][#2][]}%
+      \fi}}
+
+\def\dodosetlayer[#1][#2][#3]% #2 = links/rechts
+  {\bgroup
+   \recalculatebackgrounds % brrr
+   \global\advance\currentlayerdata\plusone
+   \forgetall
+   \dontcomplain
+   \doifvalue{\??ll#1\c!option}\v!test\tracelayerstrue
+   \iftracelayers\traceboxplacementtrue\fi
+   \dowithnextbox{\dodosetlayerindeed{#1}{#2}{#3}\egroup}\hbox}
+
+\def\dodosetlayerindeed#1#2#3% #2 = links/rechts
+  {\ifcsname\@@layerbox#1\endcsname % nb: odd/even discard, left/right not
+     \edef\@@layerloc{#2}%
+     \ifx\@@layerloc\v!even
+       \ifodd\realpageno
+       %  discard nextbox
+       \else
+         \dododosetlayer[#1][\v!left][#3]%
+       \fi
+     \else\ifx\@@layerloc\v!odd
+       \ifodd\realpageno
+         \dododosetlayer[#1][\v!right][#3]%
+      %\else
+       %  discard nextbox
+       \fi
+     \else
+       \dododosetlayer[#1][#2][#3]%
+     \fi\fi
+   \else
+     \writestatus{layer}{unknown layer #1}%
+   \fi}
+
+\newbox\layerbox
+
+\newdimen\@@layerxsiz
+\newdimen\@@layerysiz
+\newdimen\@@layerxoff
+\newdimen\@@layeryoff
+\newdimen\@@layerxpos
+\newdimen\@@layerypos
+
+\let\lastlayerxpos\!!zeropoint
+\let\lastlayerypos\!!zeropoint
+\let\lastlayerwd  \!!zeropoint
+\let\lastlayerht  \!!zeropoint
+\let\lastlayerdp  \!!zeropoint
+
+% todo left/right
+
+\def\setlastlayerpos#1%
+  {\edef\layerpage{\MPp{lyr:\the\currentlayerdata}}%
+   \xdef\lastlayerxpos{\the\dimexpr-\MPx{lyr:#1:\layerpage}+\MPx{lyr:\the\currentlayerdata}\relax}%
+   \xdef\lastlayerypos{\the\dimexpr \MPy{lyr:#1:\layerpage}-\MPy{lyr:\the\currentlayerdata}\relax}}
+
+\unexpanded\def\definelayerpreset
+ {\dodoubleargument\dodefinelayerpreset}
+
+% \def\dodefinelayerpreset[#1][#2]%
+%   {\setvalue{\??ll\??ll#1}{\dopresetlayer{#2}}}
+%
+% more fun: \definelayerpreset[whatever][lefttop]
+
+\def\dodefinelayerpreset[#1][#2]%
+  {\doifassignmentelse{#2}
+     {\setvalue{\??ll\??ll#1}{\dopresetlayer{#2}}}
+     {\setvalue{\??ll\??ll#1}{\csname\??ll\??ll#2\endcsname}}}
+
+\def\dopresetlayer#1#2#3% #1=list #2=tag #3=list
+  {\getparameters[\??ll#2][#1,#3]}
+
+\letempty\currentlayer
+
+\def\layerparameter#1{\csname\??ll\currentlayer#1\endcsname}
+
+\newdimen\layerwidth
+\newdimen\layerheight
+
+\chardef\@@lacome=1 % LAyerCOnstructionMEthod / temp, will be default
+
+\def\dododosetlayer[#1][#2][#3]% will be sped up
+  {% we use the global width, never change this
+   \def\currentlayer{#1}%
+   \@@layerxsiz\layerparameter\c!width
+   \@@layerysiz\layerparameter\c!height
+   \layerwidth \@@layerxsiz
+   \layerheight\@@layerysiz
+   % preroll
+   \getparameters[\??ll\currentlayer][#3]%
+   %
+   % \executeifdefined{\??ll\??ll\layerparameter\c!preset}\gobbletwoarguments\currentlayer{#3}%
+   %
+   \edef\@@currentlayerpreset{\layerparameter\c!preset}%
+   \ifcsname\??ll\??ll\@@currentlayerpreset\endcsname\csname\??ll\??ll\@@currentlayerpreset\endcsname\currentlayer{#3}\fi
+   %
+   \doif{\layerparameter\c!position}\v!overlay  % slow, use \dosetvalue instead
+     {\getparameters[\??ll\currentlayer][\c!width=\zeropoint,\c!height=\zeropoint,\c!position=\v!yes]}%
+   \doifsomething{\layerparameter\c!rotation}% todo: use direct lowlevel call
+     {\setbox\nextbox\hbox{\rotate[\c!location=\v!high,\c!rotation=\layerparameter\c!rotation]{\flushnextbox}}}%
+   % no, not local
+   % \@@layerxsiz\layerparameter\c!width
+   % \@@layerysiz\layerparameter\c!height
+   % never change that
+   \@@layerxpos\layerparameter\c!x
+   \@@layerypos\layerparameter\c!y
+   \doifelse{\layerparameter\c!hoffset}\v!max{\@@layerxoff\@@layerxsiz}{\@@layerxoff\layerparameter\c!hoffset}%
+   \doifelse{\layerparameter\c!voffset}\v!max{\@@layeryoff\@@layerysiz}{\@@layeryoff\layerparameter\c!voffset}%
+   % dx/dy are internal context ones and can be used in preset
+   \advance\@@layerxoff\dimexpr\layerparameter\c!offset+\layerparameter\c!dx\relax
+   \advance\@@layeryoff\dimexpr\layerparameter\c!offset+\layerparameter\c!dy\relax
+   \@@layerxpos\layerparameter\c!sx\@@layerxpos
+   \@@layerypos\layerparameter\c!sy\@@layerypos
+   \@@layerxoff\layerparameter\c!sx\@@layerxoff
+   \@@layeryoff\layerparameter\c!sy\@@layeryoff
+   \edef\@@currentlayerposition{\layerparameter\c!position}%
+   \ifx\@@currentlayerposition\v!yes   % combine ^
+     \setlastlayerpos{#2\currentlayer}% sets \layerpage; todo l/r %%%%%%%%%%%%
+     \@@layerxpos\lastlayerxpos
+     \@@layerypos\lastlayerypos
+     \letgvalue{\??ll\currentlayer\layerpage\c!position}\v!yes
+     \letgvalue{\??ll\currentlayer\c!state}\v!start % needed ?
+     \setbox\layerbox\vbox to \@@layerysiz{\hbox to \@@layerxsiz{\xypos{lyr:\the\currentlayerdata}\hss}\vss}%
+   \else
+     \setbox\layerbox\emptybox
+     \globallet\lastlayerxpos\!!zeropoint
+     \globallet\lastlayerypos\!!zeropoint
+     \normalexpanded{\noexpand\doifinset{\v!bottom}{\layerparameter\c!corner}}\dosetlayerbottompositions
+     \normalexpanded{\noexpand\doifinset{\v!right }{\layerparameter\c!corner}}\dosetlayerrightpositions
+     \normalexpanded{\noexpand\doifinset{\v!middle}{\layerparameter\c!corner}}\dosetlayermiddlepositions
+     \edef\layerpage{\layerparameter\c!page}%
+   \fi
+   \ifx\layerpage\empty \else % is expanded
+     \edef\layerpage{:\layerpage}%
+     \ifcsname\@@layerbox#2\currentlayer\layerpage\endcsname \else
+       \expandafter\newbox\csname\@@layerbox#2\currentlayer\layerpage\endcsname
+     \fi
+   \fi
+   \chardef\layerpagebox\csname\@@layerbox#2\currentlayer\layerpage\endcsname
+   \ifvoid\layerpagebox
+     \gsetboxllx\layerpagebox\zeropoint
+     \gsetboxlly\layerpagebox\zeropoint
+   \fi
+   \global\setbox\layerpagebox\vbox %to \layerparameter\c!height % new, otherwise no negative y possible
+     {\offinterlineskip
+     %postpone, to after nextboxwd correction % \hsize\layerparameter\c!width % new, keep box small
+     %\ifvoid\csname\@@layerbox\currentlayer\layerpage\endcsname\else % why not #2#1
+      \ifvoid\layerpagebox
+        \let\lastlayerwidth \zeropoint
+        \let\lastlayerheight\zeropoint
+      \else
+        \edef\lastlayerwidth {\the\wd\layerpagebox}%
+        \edef\lastlayerheight{\the\ht\layerpagebox}%
+        \ht\layerpagebox\zeropoint
+        \dp\layerpagebox\zeropoint
+        \wd\layerpagebox\zeropoint
+        \doifnot{\layerparameter\c!direction}\v!reverse{\box\layerpagebox}%
+      \fi
+      % don't move
+      \xdef\lastlayerwd{\the\nextboxwd}%
+      \xdef\lastlayerht{\the\nextboxht}% % not entirely ok when grid !
+      \xdef\lastlayerdp{\the\nextboxdp}% % not entirely ok when grid !
+      % this code
+      \doifelse{\layerparameter\c!location}\v!grid\donetrue\donefalse
+      \ifdone
+        \nextboxht\strutheight
+        \nextboxdp\strutdepth
+      \else
+        \setbox\nextbox\hbox{\alignedbox[\layerparameter\c!location]\vbox{\flushnextbox}}%
+      \fi
+      \ifnum\layerparameter\c!line=\zerocount\else % no \ifcase, can be negative
+        \advance\@@layerypos\dimexpr\layerparameter\c!line\lineheight+\topskip-\lineheight-\nextboxht\relax
+      \fi
+      \ifnum\layerparameter\c!column=\zerocount\else % no \ifcase, can be negative
+        \advance\@@layerxpos\layoutcolumnoffset{\layerparameter\c!column}%
+      \fi
+      \ifdone
+        \setbox\nextbox\hbox{\alignedbox[rb]\vbox{\flushnextbox}}%
+      \fi
+      % ll registration
+      \scratchdimen\@@layerxpos
+      \advance\scratchdimen\@@layerxoff
+      \ifdim\scratchdimen<\getboxllx\layerpagebox
+        \gsetboxllx\layerpagebox\scratchdimen
+      \fi
+      \ifcase\@@lacome\or % this test will become obsolete
+        \advance\scratchdimen\nextboxwd
+        \nextboxwd\ifdim\scratchdimen>\lastlayerwidth \scratchdimen \else \lastlayerwidth \fi
+      \fi
+      \scratchdimen\dimexpr\@@layerypos+\@@layeryoff\relax
+      \ifdim\scratchdimen<\getboxlly\layerpagebox
+        \gsetboxlly\layerpagebox\scratchdimen
+      \fi
+      % ll compensation
+      \ifcase\@@lacome\or % this test will become obsolete
+        \advance\scratchdimen\dimexpr\nextboxht+\nextboxdp\relax
+        \nextboxht\ifdim\scratchdimen>\lastlayerheight \scratchdimen \else \lastlayerheight \fi
+        \nextboxdp\zeropoint
+      \fi
+      % placement
+      \hsize\layerparameter\c!width % new, keep box small
+      \vbox to \layerparameter\c!height \bgroup
+        \smashbox\nextbox
+        \vskip\dimexpr\@@layerypos+\@@layeryoff\relax
+        \hskip\dimexpr\@@layerxpos+\@@layerxoff\relax
+        \flushnextbox
+        \ifvoid\layerpagebox
+          % already flushed
+        \else
+          % the reverse case % check !
+          \vskip-\dimexpr\@@layerypos+\@@layeryoff\relax
+          \box\layerpagebox
+        \fi
+      \egroup}%
+   % when position is true, the layerbox holds the compensation and needs
+   % to be placed; never change this !
+   \ifvoid\layerbox\else\box\layerbox\fi}
+
+\def\dosetlayerbottompositions
+  {\ifnum\layerparameter\c!line=\zerocount\else % can be < 0
+     \setevalue{\??ll\currentlayer\c!line}{\the\numexpr-\layerparameter\c!line+\layoutlines+\plusone\relax}%
+   \fi
+   \ifdim\@@layerysiz>\zeropoint
+     \advance\@@layerypos-\@@layerysiz
+     \@@layerypos-\@@layerypos
+     \@@layeryoff-\@@layeryoff
+   \fi}
+
+\def\dosetlayerrightpositions
+  {\ifnum\layerparameter\c!column=\zerocount\else % can be < 0
+     \setevalue{\??ll\currentlayer\c!column}{\the\numexpr-\layerparameter\c!column+\layoutcolumns+\plusone\relax}%
+   \fi
+   \ifdim\@@layerxsiz>\zeropoint
+     \advance\@@layerxpos-\@@layerxsiz
+     \@@layerxpos-\@@layerxpos
+     \@@layerxoff-\@@layerxoff
+   \fi}
+
+\def\dosetlayermiddlepositions
+  {\ifdim\@@layerxsiz>\zeropoint \advance\@@layerxpos.5\@@layerxsiz \fi
+   \ifdim\@@layerysiz>\zeropoint \advance\@@layerypos.5\@@layerysiz \fi}
+
+%D Given the task to be accomplished, the previous macro is
+%D not even that complicated. It mainly comes down to skipping
+%D to the right place and placing a box on top of or below the
+%D existing content. In the case of position tracking, another
+%D reference point is chosen.
+
+%D \macros
+%D  {doifelselayerdata}
+
+\def\doifelselayerdata#1%
+  {\ifcsname\@@layerbox#1\endcsname
+     \ifvoid\csname\@@layerbox#1\endcsname
+       \@EAEAEA\secondoftwoarguments
+     \else
+       \@EAEAEA\firstoftwoarguments
+     \fi
+   \else
+     \@EA\secondoftwoarguments
+   \fi}
+
+%D \macros
+%D  {flushlayer}
+%D
+%D When we flush a layer, we flush both the main one and the
+%D page dependent one (when defined). This feature is more
+%D efficient in \ETEX\ since there testing for an undefined
+%D macro does not takes hash space.
+
+% todo: setups before flush, handy hook
+
+% \unexpanded\def\flushlayer[#1]%
+%   {\doifelsevalue{\??ll#1\c!state}\v!next
+%      {\global\letvalue{\??ll#1\c!state}\v!start} % dangerous, stack-built-up
+%      {\doifelsevalue{\??ll#1\c!state}\v!continue
+%         {\global\letvalue{\??ll#1\c!state}\v!repeat} % dangerous, stack-built-up
+%         {\doifelsevalue{\??ll#1\c!doublesided}\v!yes
+%            {\doifundefinedelse{\@@layerbox#1}%
+%               {\dodoflushlayerA[#1]}
+%               {\doifbothsidesoverruled
+%                  {\dodoflushlayerB\v!left [#1]}%  left
+%                  {\dodoflushlayerB\v!right[#1]}% right
+%                  {\dodoflushlayerB\v!left [#1]}}}%  left
+%            {\dodoflushlayerA[#1]}}}}
+
+\unexpanded\def\flushlayer[#1]% quite core, so optimized
+  {\begingroup
+   \forgetall
+   \edef\currentlayer{#1}%
+   \edef\@@currentlayerstate{\csname\??ll\currentlayer\c!state\endcsname}%
+   \ifx\@@currentlayerstate\v!stop
+     % nothing
+   \else\ifx\@@currentlayerstate\v!next
+     \global\expandafter\let\csname\??ll\currentlayer\c!state\endcsname\v!start  % dangerous, stack-built-up
+   \else\ifx\@@currentlayerstate\v!continue
+     \global\expandafter\let\csname\??ll\currentlayer\c!state\endcsname\v!repeat % dangerous, stack-built-up
+   \else
+     \edef\@@currentlayerdoublesided{\csname\??ll\currentlayer\c!doublesided\endcsname}%
+     \ifx\@@currentlayerdoublesided\v!yes
+       \ifcsname\@@layerbox#1\endcsname
+         % we can make a dedicated one for this
+         \doifbothsidesoverruled{\dodoflushlayerB\v!left}{\dodoflushlayerB\v!right}{\dodoflushlayerB\v!left}%
+       \else
+         \dodoflushlayerA
+       \fi
+     \else
+        \dodoflushlayerA
+     \fi
+   \fi\fi\fi
+   \endgroup}
+
+%  \ifcase#1\else\writestatus{layer}{unknown layer #3}\fi
+
+\def\dodoflushlayerA
+  {\startoverlay
+     {\ifcsname\@@layerbox\currentlayer           \endcsname\dodoflushlayer\plusone   \currentlayer            \fi}%
+     {\ifcsname\@@layerbox\currentlayer:\realfolio\endcsname\dodoflushlayer\zerocount{\currentlayer:\realfolio}\fi}%
+   \stopoverlay}
+
+\def\dodoflushlayerB#1%
+  {\startoverlay
+     {\ifcsname\@@layerbox  \currentlayer           \endcsname\dodoflushlayer\plusone     \currentlayer            \fi}%
+     {\ifcsname\@@layerbox  \currentlayer:\realfolio\endcsname\dodoflushlayer\zerocount  {\currentlayer:\realfolio}\fi}%
+     {\ifcsname\@@layerbox#1\currentlayer           \endcsname\dodoflushlayer\plusone  {#1\currentlayer           }\fi}%
+     {\ifcsname\@@layerbox#1\currentlayer:\realfolio\endcsname\dodoflushlayer\zerocount{#1\currentlayer:\realfolio}\fi}%
+   \stopoverlay}
+
+\def\dodoflushlayer#1#2% quite core, so optimized
+  {\begingroup % already grouped
+   \offinterlineskip
+   \edef\@@currentlayermethod{\csname\??ll\currentlayer\c!method\endcsname}%
+   \edef\@@currentlayeroption{\csname\??ll\currentlayer\c!option\endcsname}%
+   % needed because we need to handle method but we should find a way to
+   % speed this up
+   \edef\@@currentlayerpreset{\csname\??ll\currentlayer\c!preset\endcsname}%
+   \ifcsname\??ll\??ll\@@currentlayerpreset\endcsname\csname\??ll\??ll\@@currentlayerpreset\endcsname\currentlayer{}\fi
+   %
+   \ifx\@@currentlayeroption\v!test
+     \tracelayerstrue
+   \fi
+   \iftracelayers
+     \traceboxplacementtrue
+   \fi
+   \!!doneafalse
+   \!!donebfalse
+   \ifx\@@currentlayermethod\v!overlay\!!doneatrue\fi
+   \ifx\@@currentlayermethod\v!fit    \!!donebtrue\fi
+   \!!donectrue
+   \ifcase#1\else
+     \edef\@@currentlayerposition{\csname\??ll\currentlayer\c!position\endcsname}%
+     \ifx\@@currentlayerposition\v!yes \else
+       \edef\@@currentlayerrepeat{\csname\??ll\currentlayer\c!repeat\endcsname}%
+     % \edef\@@currentlayerstate {\csname\??ll\currentlayer\c!state\endcsname}% actually this is already set
+       \ifx\@@currentlayerrepeat\v!yes
+         \!!donecfalse
+       \else\ifx\@@currentlayerstate\v!repeat
+         \!!donecfalse
+       \fi\fi
+     \fi
+   \fi
+   \chardef\layerbox\csname\@@layerbox#2\endcsname % \@@layerbox\currentlayer
+   % we need to copy in order to retain the negative offsets for a next
+   % stage of additions, i.e. llx/lly accumulate in repeat mode and the
+   % compensation may differ each flush depending on added content
+   \setbox\nextbox
+     \if!!doneb
+       \therepositionededlayerbox
+     \else
+       \if!!donec\box\else\copy\fi\layerbox % sorry for the delay due to copying
+     \fi
+   % todo: method=offset => overlayoffset right/down (handy for backgrounds with offset)
+   \doifoverlayelse{#2}{\setlayoutcomponentattribute\v!layer{#2}}\resetlayoutcomponentattribute
+   \iftracelayers \ruledvbox \else \vbox \fi \if!!donea to \overlayheight \fi \layoutcomponentboxattribute
+     {\hbox \if!!donea to \overlaywidth \fi
+        {\edef\@@currentlayerpageposition{\csname\??ll#2\realfolio\c!position\endcsname}%
+         \ifx\@@currentlayerpageposition\v!yes\xypos{lyr:#2:\realfolio}\fi
+         \box\nextbox
+         \hss}%
+      \vss}%
+   \if!!donec
+     \gsetboxllx\layerbox\zeropoint
+     \gsetboxlly\layerbox\zeropoint
+   \fi
+   \endgroup}
+
+\def\therepositionededlayerbox % assumes that \if!!donec is set (todo: use dedicated flags)
+  {\vbox
+     {\vskip-\getboxlly\layerbox
+      \hskip-\getboxllx\layerbox
+      \hsize-\dimexpr\getboxllx\layerbox-\wd\layerbox\relax
+      \if!!donec\box\else\copy\fi\layerbox}}
+
+% \definelayer[test][method=fit] \setupcolors[state=start] \tracelayerstrue
+%
+% \framed[framecolor=red,offset=overlay]{\setlayer[test]{aa}\setlayer[test][x=10pt]{g}\flushlayer[test]}
+% \framed[framecolor=red,offset=overlay]{\setlayer[test]{aa}\setlayer[test][x=-10pt]{bb}\flushlayer[test]}
+% \framed[framecolor=red,offset=overlay]{\setlayer[test][x=-20pt]{cccccc}\flushlayer[test]}
+% \framed[framecolor=red,offset=overlay]{\setlayer[test]{dd}\setlayer[test][x=-20pt,y=-3pt]{eeeeee}\flushlayer[test]}
+
+%D \macros
+%D  {composedlayer,placelayer,tightlayer}
+%D
+%D This is a handy shortcut, which saves a couple of braces
+%D when we use it as parameter. This name also suits better
+%D to other layering commands.
+
+\def\composedlayer#1{\flushlayer[#1]}
+
+\let\placelayer\flushlayer
+
+\def\tightlayer[#1]%
+  {\hbox
+     {\def\currentlayer{#1}% todo: left/right
+      \setbox\nextbox\emptybox       % hoogte/breedte are \wd\nextbox/\ht\nextbox
+      \hsize\layerparameter\c!width  % \overlaywidth   = \hsize
+      \vsize\layerparameter\c!height % \overlaywheight = \vsize
+      \composedlayer{#1}}}
+
+%D \macros
+%D  {resetlayer}
+%D
+%D This macro hardly needs an explanation (and is seldom
+%D needed as well).
+
+\def\doresetlayer#1%
+  {\ifcsname\@@layerbox#1\endcsname
+     \global\setbox\csname\@@layerbox#1\endcsname\emptybox
+   \fi}
+
+\def\resetlayer[#1]%
+  {\doresetlayer{#1}%
+   \doifvalue{\??ll#1\c!doublesided}\v!yes % kind of redundant test
+     {\doresetlayer{\v!left #1}%
+      \doresetlayer{\v!right#1}}%
+   \doresetlayer{#1:\realfolio}}
+
+%D \macros
+%D  {setMPlayer}
+%D
+%D The following layer macro uses the positions that are
+%D registered by \METAPOST.
+%D
+%D \starttyping
+%D \definelayer[test]
+%D
+%D \setMPlayer [test] [somepos-1] {Whatever we want here!}
+%D \setMPlayer [test] [somepos-2] {Whatever we need there!}
+%D \setMPlayer [test] [somepos-3] {\externalfigure[cow.mps][width=2cm]}
+%D
+%D \startuseMPgraphic{oeps}
+%D   draw fullcircle scaled 10cm withcolor red ;
+%D   register ("somepos-1",2cm,3cm,center currentpicture) ;
+%D   register ("somepos-2",8cm,5cm,(-1cm,-2cm)) ;
+%D   register ("somepos-3",0cm,0cm,(-2cm,2cm)) ;
+%D \stopuseMPgraphic
+%D
+%D \getMPlayer[test]{\useMPgraphic{oeps}}
+%D \stoptyping
+%D
+%D The last line is equivalent to
+%D
+%D \starttyping
+%D \framed
+%D   [background={foreground,test},offset=overlay]
+%D   {\useMPgraphic{oeps}}
+%D \stoptyping
+
+\def\setMPlayer
+  {\dotripleempty\dosetMPlayer}
+
+\def\MPlayerwidth {\hsize}
+\def\MPlayerheight{\vsize}
+
+\def\dosetMPlayer[#1][#2][#3]%
+  {\edef\MPlayerwidth {\MPw{#2}}%
+   \edef\MPlayerheight{\MPh{#2}}%
+   \setlayer[#1][\c!x=\MPx{#2},\c!y=\MPy{#2},\c!position=\v!no,#3]}
+
+\def\getMPlayer
+  {\dodoubleempty\dogetMPlayer}
+
+\def\dogetMPlayer[#1][#2]%
+  {\framed
+     [\c!background={\v!foreground,#1},
+      \c!frame=\v!off,
+      \c!offset=\v!overlay,#2]}
+
+% The next mechanism is obsolete and will be removed in \MKIV\ (or move to
+% the compatibility module.
+
+\newskip\xposition  \newskip\yposition
+\newskip\xdimension \newskip\ydimension
+\newskip\xoffset    \newskip\yoffset
+
+% already defined \newbox\positionbox
+
+\unexpanded\def\startpositioning
+  {\bgroup
+   \xposition \zeropoint     \yposition \zeropoint
+   \xdimension\zeropoint     \ydimension\zeropoint
+   \xoffset   \zeropoint     \yoffset   \zeropoint
+   \hfuzz     \paperwidth \vfuzz     \paperheight
+   \setbox\positionbox\hbox\bgroup}
+
+\unexpanded\def\stoppositioning
+  {\doifnot\@@psoffset\v!yes
+     {\global\xoffset\zeropoint
+      \global\yoffset\zeropoint}%
+   \global\advance\xdimension \xoffset
+   \global\advance\ydimension \yoffset
+   \egroup
+   \vbox to \ydimension
+     {\vskip\yoffset
+      \hbox to \xdimension
+        {\hskip\xoffset
+         \box\positionbox
+         \hfill}
+      \vfill}%
+   \egroup}
+
+\def\resetpositioning
+  {\getparameters[\??ps]
+     [\c!state=\v!start,%
+      \c!unit=\s!cm,%
+      \c!factor=1,%
+      \c!scale=1,%
+      \c!xfactor=\@@psfactor,%
+      \c!yfactor=\@@psfactor,%
+      \c!xscale=\@@psscale,%
+      \c!yscale=\@@psscale,%
+      \c!xstep=\v!absolute,%
+      \c!ystep=\v!absolute,%
+      \c!xoffset=\!!zeropoint,%
+      \c!yoffset=\!!zeropoint]}
+
+\unexpanded\def\setuppositioning
+  {\resetpositioning
+   \dodoubleargument\getparameters[\??ps]}
+
+\def\calculateposition#1#2#3#4#5#6#7#8#9%
+  {\setdimensionwithunit\scratchskip{#1}\@@psunit
+   \scratchskip#8\scratchskip
+   \scratchskip#9\scratchskip
+   \advance\scratchskip #4\relax
+   \doif{#2}\v!relative
+     {\advance\scratchskip #3%
+      \let#4\!!zeropoint}%
+   #3\scratchskip\relax
+   \doifnot\@@psstate\v!overlay
+     {\scratchskip#5\relax
+      \advance\scratchskip #3\relax
+      \ifdim#3<-#7\relax          \global#7-#3\relax          \fi
+      \ifdim\scratchskip>#6\relax \global#6\scratchskip\relax \fi}}
+
+\def\position
+  {\dosingleempty\doposition}
+
+\def\doposition[#1]#2(#3,#4)%
+  {\dowithnextbox
+     {\bgroup
+      \getparameters[\??ps][#1]%
+      \dontcomplain
+      \calculateposition{#3}\@@psxstep\xposition
+        \@@psxoffset{\nextboxwd}\xdimension\xoffset
+        \@@psxscale\@@psxfactor
+      \scratchdimen\nextboxht \advance\scratchdimen \nextboxdp
+      \calculateposition{#4}\@@psystep\yposition
+        \@@psyoffset\scratchdimen\ydimension\yoffset
+        \@@psyscale\@@psyfactor
+      \vbox to \zeropoint % kan beter.
+        {\vskip\yposition
+         \hbox to \zeropoint
+           {\hskip\xposition
+            \flushnextbox
+            \hss}
+         \vss}%
+      \xdef\dopoppositioning
+        {\xposition\the\xposition
+         \yposition\the\yposition
+         \noexpand\def\noexpand\@@psxoffset{\@@psxoffset}%
+         \noexpand\def\noexpand\@@psyoffset{\@@psyoffset}}%
+      \egroup
+      \dopoppositioning
+      \ignorespaces}
+   \hbox}
+
+\resetpositioning
+
+\setuppositioning
+  [\c!unit=\s!cm,
+   \c!factor=1,
+   \c!scale=1,
+   \c!xstep=\v!absolute,
+   \c!ystep=\v!absolute,
+   \c!offset=\v!yes,
+   \c!xoffset=\!!zeropoint,
+   \c!yoffset=\!!zeropoint]
+
+%D Watch out, a redefinition:
+
+\ifx\settextpagecontent\undefined \writestatus\m!systems{error in page-lyr.tex} \wait \fi
+
+\let\normalsettextpagecontent\settextpagecontent
+
+\definelayer
+  [OTRTEXT]
+
+\setuplayer
+  [OTRTEXT]
+  [\c!width=\innermakeupwidth,
+   \c!height=\textheight]
+
+% will be overloaded in page-spr
+
+\def\settextpagecontent#1#2#3% #2 and #3 will disappear
+  {\doifelselayerdata{OTRTEXT}
+     {\setbox#1\hbox to \makeupwidth
+        {\startoverlay
+           {\tightlayer[OTRTEXT]} % first, otherwise problems with toc
+           {\normalsettextpagecontent{#1}{#2}{#3}\box#1}
+         \stopoverlay}%
+      \dp#1\zeropoint}%
+     {\normalsettextpagecontent{#1}{#2}{#3}}}
+
+\protect \endinput
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