1 files changed, 794 insertions, 0 deletions
diff --git a/tex/context/base/mkiv/pack-lyr.mkxl b/tex/context/base/mkiv/pack-lyr.mkxl
new file mode 100644
index 000000000..838e2fe19
--- /dev/null
+++ b/tex/context/base/mkiv/pack-lyr.mkxl
@@ -0,0 +1,794 @@
+%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 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 / 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).
+
+%D The layering mechanism implemented here is independent of the output routine, but
+%D future extensions may depend on a more close cooperation.
+%D
+%D First we overload a macro from \type {pack-rul}. From now on we accept a
+%D (optional) argument: the specific layer it will go in. This means that we can
+%D move an overlay from one background to the other using the dimensions of the
+%D parent.
+
+\ifdefined\defineoverlay \else \message{loaded to early} \wait \fi
+
+\unexpanded\def\defineoverlay
+  {\dotripleempty\pack_framed_define_overlay}
+
+\def\pack_framed_define_overlay[#1][#2][#3]% overlay [layer] content
+  {\ifthirdargument
+    %\writestatus{BEWARE}{This (overlay definition) has changed!}% temp
+     \def\pack_framed_define_overlay_indeed##1{\setvalue{\??overlay##1}{\setlayer[#2]{\executedefinedoverlay{##1}{#3}}}}%
+   \else
+     \def\pack_framed_define_overlay_indeed##1{\setvalue{\??overlay##1}{\executedefinedoverlay{##1}{#2}}}%
+   \fi
+   \processcommalist[#1]\pack_framed_define_overlay_indeed}
+
+%D We use the command handler code. The previous, more direct parameter handling was
+%D 25\% faster when no parameters were passed when adding content to a layer.
+%D However, when we pass for instance a preset, the new methos is some 10\% faster
+%D and it happens that in most cases we do pass some parameters. It would be
+%D interesting to see if we can push the preset in between the regular chain but it
+%D could also lead to unwanted side effects when nesting layer placement.
+
+\installcorenamespace{layer}
+\installcorenamespace{layerbox}
+\installcorenamespace{layerpreset}
+\installcorenamespace{layerposition} % brr, unreadable
+
+%D \macros
+%D   {definelayer,setuplayer}
+%D
+%D Each layer gets its own (global) box. This also means that the data that goes
+%D into a layer, is typeset immediately. Each layer automatically gets an associated
+%D overlay, which can be used in any background assignment.
+%D
+%D After a layer is defined, you can change its characteristics.
+
+\installcommandhandler \??layer {layer} \??layer
+
+\setuplayer
+  [\c!state=\v!start,
+  %\c!doublesided=,
+  %\c!preset=,
+  %\c!option=,
+  %\c!corner=,
+  %\c!page=,
+  %\c!rotation=, % geen 0 !
+   \c!direction=\v!normal,
+   \c!position=\v!no,
+   \c!method=\v!overlay,
+   \c!x=\zeropoint,
+   \c!y=\zeropoint,
+   \c!line=0,
+   \c!column=0,
+   \c!width=\wd\nextbox,  % don't change this globally
+   \c!height=\ht\nextbox, % don't change this globally
+   \c!offset=\zeropoint,
+   \c!hoffset=\zeropoint,
+   \c!voffset=\zeropoint,
+   \c!dx=\zeropoint,
+   \c!dy=\zeropoint,
+   \c!location=rb,
+   \c!sx=1,
+   \c!sy=1,
+   \c!region=\layeranchor]
+
+\def\layeranchor{\currentlayer:\the\realpageno}
+
+\let\p_pack_layers_doublesided\empty
+\let\p_pack_layers_state      \empty
+\let\p_pack_layers_option     \empty
+\let\p_pack_layers_method     \empty
+\let\p_pack_layers_preset     \empty
+\let\p_pack_layers_rotation   \empty
+\let\p_pack_layers_position   \empty
+\let\p_pack_layers_hoffset    \empty
+\let\p_pack_layers_voffset    \empty
+\let\p_pack_layers_offset     \empty
+\let\p_pack_layers_dx         \empty
+\let\p_pack_layers_dy         \empty
+\let\p_pack_layers_sx         \empty
+\let\p_pack_layers_sy         \empty
+\let\p_pack_layers_x          \empty
+\let\p_pack_layers_y          \empty
+\let\p_pack_layers_corner     \empty
+\let\p_pack_layers_location   \empty
+\let\p_pack_layers_line       \empty
+\let\p_pack_layers_column     \empty
+\let\p_pack_layers_width      \empty
+\let\p_pack_layers_height     \empty
+\let\p_pack_layers_direction  \empty
+\let\p_pack_layers_region     \empty
+
+\let\m_pack_layers_page       \empty
+\let\m_pack_layers_target     \empty
+\let\m_pack_layers_region     \empty
+\let\m_pack_layers_anchor     \empty
+
+\newconditional\c_pack_layers_repeated
+\newconditional\c_pack_layers_trace
+\newcount      \c_pack_layers_current_data
+
+\newbox\b_layers
+
+\newdimen\d_pack_layers_x_size
+\newdimen\d_pack_layers_y_size
+\newdimen\d_pack_layers_x_offset
+\newdimen\d_pack_layers_y_offset
+\newdimen\d_pack_layers_x_position
+\newdimen\d_pack_layers_y_position
+
+\newdimen\layerwidth
+\newdimen\layerheight
+
+\let\lastlayerxpos\!!zeropoint
+\let\lastlayerypos\!!zeropoint
+\let\lastlayerwd  \!!zeropoint
+\let\lastlayerht  \!!zeropoint
+\let\lastlayerdp  \!!zeropoint
+
+\appendtoks
+    \edef\p_pack_layers_doublesided{\layerparameter\c!doublesided}%
+    \ifx\p_pack_layers_doublesided\v!yes
+        \relateparameterhandlers{layer}{\v!left \currentlayer}{layer}\currentlayer % permits left*
+        \relateparameterhandlers{layer}{\v!right\currentlayer}{layer}\currentlayer % permits right*
+        \pack_layers_preset_box{\v!left \currentlayer}%
+        \pack_layers_preset_box{\v!right\currentlayer}%
+    \fi
+    \pack_layers_preset_box\currentlayer
+    \normalexpanded{\defineoverlay[\currentlayer][\noexpand\composedlayer{\currentlayer}]}%
+\to \everydefinelayer
+
+\def\pack_layers_preset_box#1%
+  {\ifcsname\??layerbox#1\endcsname
+     \resetlayer[#1]%
+   \else
+     \expandafter\newbox\csname\??layerbox#1\endcsname
+   \fi}
+
+%D \macros
+%D  {resetlayer}
+%D
+%D This macro hardly needs an explanation (but is seldom needed anyway).
+
+\def\pack_layers_reset_box#1%
+  {\ifcsname\??layerbox#1\endcsname
+    %\global\setbox\csname\??layerbox#1\endcsname\emptybox
+     \global\setbox\lastnamedcs\emptybox
+   \fi}
+
+\def\resetlayer[#1]%
+  {\pack_layers_reset_box{#1}%
+   \pack_layers_reset_box{\v!left #1}%
+   \pack_layers_reset_box{\v!right#1}%
+   \pack_layers_reset_box{#1:\the\realpageno}}
+
+%D \macros
+%D   {setlayer}
+%D
+%D Data is moved into a layer with the following macro. When \type {position} is
+%D set, relative positioning is used, with the current point as reference point.
+%D Otherwise the topleft corner is used as reference point.
+%D
+%D \starttyping
+%D \setlayer [identifier] [optional parameters] {data}
+%D \stoptyping
+
+\def\setcurrentlayerdimensions
+  {\dodoubleempty\pack_layers_set_current_dimensions}
+
+\def\pack_layers_set_current_dimensions[#1][#2]% name left|right
+  {\edef\currentlayerwidth {\thelayerwidth {#2#1}}%
+   \edef\currentlayerheight{\thelayerheight{#2#1}}}
+
+\def\thelayerwidth #1{\the\ifcsname\??layerbox#1\endcsname\wd\lastnamedcs\else\zeropoint\fi}
+\def\thelayerheight#1{\the\ifcsname\??layerbox#1\endcsname\ht\lastnamedcs\else\zeropoint\fi}
+
+\unexpanded\def\setlayer
+  {\dotripleempty\pack_layers_set}
+
+\def\pack_layers_set[#1][#2][#3]% #4 == box do \fi is ok
+  {\bgroup
+   \checkpositionoverlays % otherwise funny regions
+   \edef\currentlayer{#1}%
+   \edef\p_pack_layers_state{\layerparameter\c!state}%
+   \ifx\p_pack_layers_state\v!stop
+     \dowithnextboxcs\egroup\hbox % no pack ?
+   \orelse\ifthirdargument
+     \pack_layers_set_indeed[#1][#2][#3]%
+   \else
+      \ifcondition\validassignment{#2}%
+        \pack_layers_set_indeed[#1][][#2]%
+      \else
+        \pack_layers_set_indeed[#1][#2][]%
+      \fi
+   \fi}
+
+\def\pack_layers_set_indeed[#1][#2][#3]% #2 = links/rechts
+  {\page_backgrounds_recalculate % brrr
+   \global\advance\c_pack_layers_current_data\plusone
+   \forgetall
+   \dontcomplain
+   \edef\p_pack_layers_option{\layerparameter\c!option}%
+   \ifx\p_pack_layers_option\v!test
+     \settrue\c_pack_layers_trace
+     \traceboxplacementtrue
+   \fi
+   \edef\m_pack_layers_target{#2}%
+   \dowithnextbox{\pack_layers_set_finish{#3}}\hbox}
+
+\def\pack_layers_set_finish#1%
+  {\ifcsname\??layerbox\currentlayer\endcsname % can move up
+     \ifx\m_pack_layers_target\v!even
+       \ifodd\realpageno
+         % discard nextbox
+       \else
+         \let\m_pack_layers_target\v!left
+         \pack_layers_set_content{#1}%
+       \fi
+     \orelse\ifx\m_pack_layers_target\v!odd
+       \ifodd\realpageno
+         \let\m_pack_layers_target\v!right
+         \pack_layers_set_content{#1}%
+       \else
+         % discard nextbox
+       \fi
+     \else
+       \pack_layers_set_content{#1}%
+     \fi
+   \else
+     \writestatus{layer}{unknown layer \currentlayer}%
+   \fi
+   \egroup}
+
+% todo: left/right
+% todo: get position data in one go
+
+\def\pack_layers_set_last_position_yes % target: left|right
+  {% this will become one call
+   \edef\m_pack_layers_anchor{\??layerposition\the\c_pack_layers_current_data}%
+   \edef\m_pack_layers_page  {\MPp\m_pack_layers_anchor}%
+   %edef\m_pack_layers_region{\MPr\m_pack_layers_anchor}% wrong one
+   \edef\m_pack_layers_region{\layerparameter\c!region}%
+   \d_pack_layers_x_position \dimexpr-\MPx\m_pack_layers_region+\MPx\m_pack_layers_anchor\relax
+   \d_pack_layers_y_position \dimexpr \MPy\m_pack_layers_region-\MPy\m_pack_layers_anchor+\MPh\m_pack_layers_region\relax
+   \xdef\lastlayerxpos{\the\d_pack_layers_x_position}%
+   \xdef\lastlayerypos{\the\d_pack_layers_y_position}%
+ % \writestatus{layering}{region: \m_pack_layers_region=>\MPxywhd\m_pack_layers_region}%
+ % \writestatus        {}{anchor: \m_pack_layers_anchor=>\MPxywhd\m_pack_layers_anchor}%
+ % \writestatus        {}{offset: \c!dx,\c!dy          =>\lastlayerxpos,\lastlayerypos}%
+   \global\letlayerparameter\c!state\v!start % needed ?
+   \setbox\b_layers\vpack to \d_pack_layers_y_size
+     {\hpack to \d_pack_layers_x_size
+        {\xypos\m_pack_layers_anchor\hss}%
+      \vss}}
+
+\def\pack_layers_set_last_position_nop
+  {\setbox\b_layers\emptybox
+   \d_pack_layers_x_position\p_pack_layers_sx\dimexpr\p_pack_layers_x\relax
+   \d_pack_layers_y_position\p_pack_layers_sy\dimexpr\p_pack_layers_y\relax
+   \glet\lastlayerxpos\!!zeropoint
+   \glet\lastlayerypos\!!zeropoint
+   \doifinset\v!bottom\p_pack_layers_corner\pack_layers_set_bottom_positions
+   \doifinset\v!right \p_pack_layers_corner\pack_layers_set_right_positions
+   \doifinset\v!middle\p_pack_layers_corner\pack_layers_set_middle_positions
+   \edef\m_pack_layers_page{\layerparameter\c!page}}
+
+\unexpanded\def\definelayerpreset
+  {\dodoubleargument\pack_layers_define_preset}
+
+\def\pack_layers_define_preset[#1][#2]%
+  {\doifelseassignment{#2}
+     {\setvalue{\??layerpreset#1}{\setupcurrentlayer[#2]}}
+     {\setvalue{\??layerpreset#1}{\csname\??layerpreset#2\endcsname}}}
+
+\def\pack_layers_set_content#1%
+  {\layerwidth \layerparameter\c!width  % global (local later)
+   \layerheight\layerparameter\c!height % global (local later)
+   \d_pack_layers_x_size\layerwidth
+   \d_pack_layers_y_size\layerheight
+   %
+   \setupcurrentlayer[#1]% preroll
+   %
+   \edef\p_pack_layers_preset   {\layerparameter\c!preset  }%
+   %
+   \ifcsname\??layerpreset\p_pack_layers_preset\endcsname
+     \lastnamedcs
+     \setupcurrentlayer[#1]% postroll
+   \fi
+   %
+   \edef\p_pack_layers_rotation {\layerparameter\c!rotation }%
+   \edef\p_pack_layers_position {\layerparameter\c!position }%
+   \edef\p_pack_layers_hoffset  {\layerparameter\c!hoffset  }%
+   \edef\p_pack_layers_voffset  {\layerparameter\c!voffset  }%
+   \edef\p_pack_layers_offset   {\layerparameter\c!offset   }%
+   \edef\p_pack_layers_dx       {\layerparameter\c!dx       }%
+   \edef\p_pack_layers_dy       {\layerparameter\c!dy       }%
+   \edef\p_pack_layers_sx       {\layerparameter\c!sx       }%
+   \edef\p_pack_layers_sy       {\layerparameter\c!sy       }%
+   \edef\p_pack_layers_x        {\layerparameter\c!x        }%
+   \edef\p_pack_layers_y        {\layerparameter\c!y        }%
+   \edef\p_pack_layers_corner   {\layerparameter\c!corner   }%
+   \edef\p_pack_layers_location {\layerparameter\c!location }%
+   \edef\p_pack_layers_line     {\layerparameter\c!line     }%
+   \edef\p_pack_layers_column   {\layerparameter\c!column   }%
+   \edef\p_pack_layers_width    {\layerparameter\c!width    }% local ones
+   \edef\p_pack_layers_height   {\layerparameter\c!height   }% local ones
+   \edef\p_pack_layers_direction{\layerparameter\c!direction}%
+   %
+   \ifx\p_pack_layers_position\v!overlay
+     \let\p_pack_layers_width   \zeropoint
+     \let\p_pack_layers_height  \zeropoint
+     \let\p_pack_layers_position\v!yes
+   \fi
+   \ifx\p_pack_layers_rotation\empty \else
+     % use direct call
+     \setbox\nextbox\hpack
+       {\rotate[\c!location=\v!high,\c!rotation=\layerparameter\c!rotation]{\box\nextbox}}%
+   \fi
+   \d_pack_layers_x_offset\p_pack_layers_sx\dimexpr
+     \ifx\p_pack_layers_hoffset\v!max\d_pack_layers_x_size\else\p_pack_layers_hoffset\fi+\p_pack_layers_offset+\p_pack_layers_dx
+   \relax
+   \d_pack_layers_y_offset\p_pack_layers_sy\dimexpr
+     \ifx\p_pack_layers_voffset\v!max\d_pack_layers_y_size\else\p_pack_layers_voffset\fi+\p_pack_layers_offset+\p_pack_layers_dy
+   \relax
+   \ifx\p_pack_layers_position\v!yes
+     \pack_layers_set_last_position_yes
+   \else
+     \pack_layers_set_last_position_nop
+   \fi
+   %
+   \ifx\m_pack_layers_page\empty \else % is expanded
+     \edef\m_pack_layers_page{:\m_pack_layers_page}%
+     \ifcsname\??layerbox\m_pack_layers_target\currentlayer\m_pack_layers_page\endcsname \else
+       \expandafter\newbox\csname\??layerbox\m_pack_layers_target\currentlayer\m_pack_layers_page\endcsname
+     \fi
+   \fi
+   \chardef\layerpagebox\csname\??layerbox\m_pack_layers_target\currentlayer\m_pack_layers_page\endcsname
+   \ifvoid\layerpagebox
+     \gsetboxllx\layerpagebox\zeropoint
+     \gsetboxlly\layerpagebox\zeropoint
+   \fi
+   \global\setbox\layerpagebox\vpack %to \layerparameter\c!height % new, otherwise no negative y possible
+     {\offinterlineskip
+      \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
+        \ifx\p_pack_layers_direction\v!reverse\else
+          \box\layerpagebox
+        \fi
+      \fi
+      % don't move
+      \xdef\lastlayerwd{\the\wd\nextbox}%
+      \xdef\lastlayerht{\the\ht\nextbox}% % not entirely ok when grid !
+      \xdef\lastlayerdp{\the\dp\nextbox}% % not entirely ok when grid !
+      % this code
+      \ifx\p_pack_layers_location\v!grid
+        \ht\nextbox\strutheight
+        \dp\nextbox\strutdepth
+      \else
+        \setbox\nextbox\hpack
+          {\alignedbox[\p_pack_layers_location]\vpack{\box\nextbox}}%
+      \fi
+      \ifnum\p_pack_layers_line=\zerocount\else % no \ifcase, can be negative
+        \advance\d_pack_layers_y_position\dimexpr\p_pack_layers_line\lineheight+\topskip-\lineheight-\ht\nextbox\relax
+      \fi
+      \ifnum\p_pack_layers_column=\zerocount\else % no \ifcase, can be negative
+        \advance\d_pack_layers_x_position\layoutcolumnoffset\p_pack_layers_column\relax
+      \fi
+      \ifx\p_pack_layers_location\v!grid
+        \setbox\nextbox\hpack
+          {\alignedbox[rb]\vpack{\box\nextbox}}%
+      \fi
+      % ll registration
+      \scratchdimen\dimexpr\d_pack_layers_x_position+\d_pack_layers_x_offset\relax
+      \ifdim\scratchdimen<\getboxllx\layerpagebox
+        \gsetboxllx\layerpagebox\scratchdimen
+      \fi
+      \advance\scratchdimen\wd\nextbox
+      \wd\nextbox\ifdim\scratchdimen>\lastlayerwidth \scratchdimen \else \lastlayerwidth \fi
+      \scratchdimen\dimexpr\d_pack_layers_y_position+\d_pack_layers_y_offset\relax
+      \ifdim\scratchdimen<\getboxlly\layerpagebox
+        \gsetboxlly\layerpagebox\scratchdimen
+      \fi
+      % ll compensation
+      \advance\scratchdimen\dimexpr\ht\nextbox+\dp\nextbox\relax
+      \ht\nextbox\ifdim\scratchdimen>\lastlayerheight \scratchdimen \else \lastlayerheight \fi
+      \dp\nextbox\zeropoint
+      % placement
+      \hsize\p_pack_layers_width
+      \vpack to \p_pack_layers_height \bgroup
+        \smashbox\nextbox
+        \vskip\dimexpr\d_pack_layers_y_position+\d_pack_layers_y_offset\relax
+        \hskip\dimexpr\d_pack_layers_x_position+\d_pack_layers_x_offset\relax
+        % or maybe instead of the \vskip
+        % \raise-\dimexpr\d_pack_layers_y_position+\d_pack_layers_y_offset\relax
+        \box\nextbox
+        \ifvoid\layerpagebox
+          % already flushed
+        \else
+          % the reverse case % check !
+          \vskip-\dimexpr\d_pack_layers_y_position+\d_pack_layers_y_offset\relax
+          \box\layerpagebox
+        \fi
+      \egroup}%
+   % when position is true, the layerbox holds the compensation and needs
+   % to be placed; never change this !
+   \ifvoid\b_layers \else
+     \box\b_layers
+   \fi}
+
+\def\pack_layers_set_bottom_positions
+  {\ifnum\p_pack_layers_line=\zerocount\else % can be < 0
+     \edef\p_pack_layers_line{\the\numexpr-\p_pack_layers_line+\layoutlines+\plusone\relax}% use counter instead ?
+   \fi
+   \ifdim\d_pack_layers_y_size>\zeropoint
+     \advance\d_pack_layers_y_position-\d_pack_layers_y_size
+     \d_pack_layers_y_position-\d_pack_layers_y_position
+     \d_pack_layers_y_offset-\d_pack_layers_y_offset
+   \fi}
+
+\def\pack_layers_set_right_positions
+  {\ifnum\p_pack_layers_column=\zerocount\else % can be < 0
+     \edef\p_pack_layers_column{\the\numexpr-\layerparameter\c!column+\layoutcolumns+\plusone\relax}% use counter instead ?
+   \fi
+   \ifdim\d_pack_layers_x_size>\zeropoint
+     \advance\d_pack_layers_x_position-\d_pack_layers_x_size
+     \d_pack_layers_x_position-\d_pack_layers_x_position
+     \d_pack_layers_x_offset-\d_pack_layers_x_offset
+   \fi}
+
+\def\pack_layers_set_middle_positions
+  {\ifdim\d_pack_layers_x_size>\zeropoint \advance\d_pack_layers_x_position.5\d_pack_layers_x_size \fi
+   \ifdim\d_pack_layers_y_size>\zeropoint \advance\d_pack_layers_y_position.5\d_pack_layers_y_size \fi}
+
+%D Given the task to be accomplished, the previous macro is not even that
+%D complicated. It mainly comes down to skipping to the right place and placing a
+%D box on top of or below the existing content. In the case of position tracking,
+%D another reference point is chosen.
+
+%D \macros
+%D  {doifelselayerdata}
+
+\def\doifelselayerdata#1%
+  {\ifcsname\??layerbox#1\endcsname
+    %\ifvoid\csname\??layerbox#1\endcsname
+     \ifvoid\lastnamedcs
+       \doubleexpandafter\secondoftwoarguments
+     \else
+       \doubleexpandafter\firstoftwoarguments
+     \fi
+   \else
+     \expandafter\secondoftwoarguments
+   \fi}
+
+\let\doiflayerdataelse\doifelselayerdata
+
+%D \macros
+%D  {flushlayer}
+%D
+%D When we flush a layer, we flush both the main one and the page dependent one
+%D (when defined). This feature is more efficient in \ETEX\ since there testing for
+%D an undefined macro does not takes hash space.
+
+% todo: setups before flush, handy hook
+
+\unexpanded\def\flushlayer[#1]% quite core, so optimized (todo: check for void)
+  {\begingroup
+   \forgetall
+   \edef\currentlayer{#1}%
+   \edef\p_pack_layers_state{\layerparameter\c!state}%
+   \ifx\p_pack_layers_state\v!stop
+     % nothing
+   \orelse\ifx\p_pack_layers_state\v!next
+     \global\letlayerparameter\c!state\v!start  % dangerous, stack-built-up
+   \orelse\ifx\p_pack_layers_state\v!continue
+     \global\letlayerparameter\c!state\v!repeat % dangerous, stack-built-up
+   \else
+     \edef\p_pack_layers_doublesided{\layerparameter\c!doublesided}%
+     \ifx\p_pack_layers_doublesided\v!yes
+       \ifcsname\??layerbox#1\endcsname
+         % we can make a dedicated one for this
+         \doifbothsidesoverruled
+           {\pack_layers_flush_double\v!left }%
+           {\pack_layers_flush_double\v!right}%
+           {\pack_layers_flush_double\v!left }%
+       \else
+         \pack_layers_flush_single
+       \fi
+     \else
+       \pack_layers_flush_single
+     \fi
+   \fi
+   \endgroup}
+
+% \def\pack_layers_flush_single
+%   {\startoverlay
+%      {\ifcsname\??layerbox  \currentlayer                \endcsname\pack_layers_flush_indeed\plusone   \currentlayer                 \fi}%
+%      {\ifcsname\??layerbox  \currentlayer:\the\realpageno\endcsname\pack_layers_flush_indeed\zerocount{\currentlayer:\the\realpageno}\fi}%
+%    \stopoverlay}
+%
+% \def\pack_layers_flush_double#1%
+%   {\startoverlay
+%      {\ifcsname\??layerbox  \currentlayer                \endcsname\pack_layers_flush_indeed\plusone     \currentlayer                 \fi}%
+%      {\ifcsname\??layerbox  \currentlayer:\the\realpageno\endcsname\pack_layers_flush_indeed\zerocount  {\currentlayer:\the\realpageno}\fi}%
+%      {\ifcsname\??layerbox#1\currentlayer                \endcsname\pack_layers_flush_indeed\plusone  {#1\currentlayer                }\fi}%
+%      {\ifcsname\??layerbox#1\currentlayer:\the\realpageno\endcsname\pack_layers_flush_indeed\zerocount{#1\currentlayer:\the\realpageno}\fi}%
+%    \stopoverlay}
+
+% optimized:
+
+\def\pack_layers_flush_single
+  {\ifcsname\??layerbox\currentlayer\endcsname
+     \ifvoid\lastnamedcs
+       \ifcsname\??layerbox\currentlayer:\the\realpageno\endcsname
+         \ifvoid\lastnamedcs\else
+           \chardef\b_layer_two\lastnamedcs
+           \pack_layers_flush_indeed\zerocount{\currentlayer:\the\realpageno}\b_layer_two
+         \fi
+       \fi
+     \else
+       \chardef\b_layer_one\lastnamedcs
+       \ifcsname\??layerbox\currentlayer:\the\realpageno\endcsname
+         \ifvoid\lastnamedcs\else
+           \chardef\b_layer_two\lastnamedcs
+           \startoverlay
+             {\pack_layers_flush_indeed\plusone   \currentlayer                 \b_layer_one}%
+             {\pack_layers_flush_indeed\zerocount{\currentlayer:\the\realpageno}\b_layer_two}%
+           \stopoverlay
+         \fi
+       \else
+         \pack_layers_flush_indeed\plusone\currentlayer\b_layer_one
+       \fi
+     \fi
+   \orelse\ifcsname\??layerbox\currentlayer:\the\realpageno\endcsname
+     \ifvoid\lastnamedcs
+        % nothing
+     \else
+       \chardef\b_layer_two\lastnamedcs
+       \pack_layers_flush_indeed\zerocount{\currentlayer:\the\realpageno}\b_layer_two
+     \fi
+   \fi}
+
+% less optimized:
+
+\def\pack_layers_flush_double#1%
+  {\startoverlay
+     {\ifcsname\??layerbox\currentlayer\endcsname
+        \ifvoid\lastnamedcss\else \chardef\b_layer_two\lastnamedcs
+          \pack_layers_flush_indeed\plusone\currentlayer\b_layer_two
+        \fi
+      \fi}%
+     {\ifcsname\??layerbox\currentlayer:\the\realpageno\endcsname
+        \ifvoid\lastnamedcss\else \chardef\b_layer_two\lastnamedcs
+          \pack_layers_flush_indeed\zerocount{\currentlayer:\the\realpageno}\b_layer_two
+        \fi
+      \fi}%
+     {\ifcsname\??layerbox#1\currentlayer\endcsname
+        \ifvoid\lastnamedcss\else \chardef\b_layer_two\lastnamedcs
+          \pack_layers_flush_indeed\plusone{#1\currentlayer}\b_layer_two
+        \fi
+      \fi}%
+     {\ifcsname\??layerbox#1\currentlayer:\the\realpageno\endcsname
+        \ifvoid\lastnamedcss\else \chardef\b_layer_two\lastnamedcs
+          \pack_layers_flush_indeed\zerocount{#1\currentlayer:\the\realpageno}\b_layer_two
+        \fi
+      \fi}%
+   \stopoverlay}
+
+\let\pack_layers_top_fill   \relax
+\let\pack_layers_bottom_fill\vss
+
+%def\pack_layers_flush_indeed#1#2%
+\def\pack_layers_flush_indeed#1#2#3%
+  {\begingroup % already grouped
+   \offinterlineskip
+   \edef\p_pack_layers_preset{\layerparameter\c!preset}%
+   \ifcsname\??layerpreset\p_pack_layers_preset\endcsname
+     \lastnamedcs
+   \fi
+   \edef\p_pack_layers_method{\layerparameter\c!method}%
+   \edef\p_pack_layers_option{\layerparameter\c!option}%
+   \ifx\p_pack_layers_option\v!test
+     \settrue\c_pack_layers_trace
+     \traceboxplacementtrue
+   \fi
+   \ifcase#1\relax
+     \setfalse\c_pack_layers_repeated
+   \else
+     \edef\p_pack_layers_position{\layerparameter\c!position}%
+     \ifx\p_pack_layers_position\v!yes
+       \setfalse\c_pack_layers_repeated
+     \else
+       \edef\p_pack_layers_repeat{\layerparameter\c!repeat}%
+       \ifx\p_pack_layers_repeat\v!yes
+         \settrue\c_pack_layers_repeated
+       \orelse\ifx\p_pack_layers_state\v!repeat
+         \settrue\c_pack_layers_repeated
+       \else
+         \setfalse\c_pack_layers_repeated
+       \fi
+     \fi
+   \fi
+   %chardef\b_layers\csname\??layerbox#2\endcsname % trick
+   \let\b_layers#3%
+   % 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
+     \ifx\p_pack_layers_method\v!fit
+       \pack_layers_positioned_box_yes
+     \else
+       \pack_layers_positioned_box_nop
+     \fi
+   % todo: method=offset => overlayoffset right/down (handy for backgrounds with offset)
+   \doifelseoverlay{#2}%
+     {\setlayoutcomponentattribute{\v!layer:#2}}%
+     \resetlayoutcomponentattribute
+   % we have conflicting demands: some mechanisms want ll anchoring .. I need to figure this out
+   % and maybe we will have 'origin=bottom' or so
+   \setbox\nextbox
+   \ifx\p_pack_layers_option\v!test \ruledvbox \else \vpack \fi \ifx\p_pack_layers_method\v!overlay to \d_overlay_height \fi \layoutcomponentboxattribute
+     {\pack_layers_top_fill
+%
+%       \hpack \ifx\p_pack_layers_method\v!overlay to \d_overlay_width \fi
+%         {\box\nextbox
+%          \hss}%
+%
+      \ifx\p_pack_layers_method\v!overlay \wd\nextbox\d_overlay_width\fi
+      \box\nextbox
+%
+      \pack_layers_bottom_fill}%
+   % \edef\currentlayer{#2}% :\the\realpageno}% local .. check \anchor
+   % \edef\p_pack_layers_position{\layerparameter\c!position}% local
+   \ifx\p_pack_layers_position\v!yes
+     \edef\p_pack_layers_region{\layerparameter\c!region}%
+     \ifx\p_pack_layers_region\empty
+     \else
+       \anch_mark_tagged_box\nextbox\p_pack_layers_region % was \layeranchor
+     \fi
+   \fi
+   \box\nextbox
+   %
+   \ifconditional\c_pack_layers_repeated\else
+     \gsetboxllx\b_layers\zeropoint
+     \gsetboxlly\b_layers\zeropoint
+   \fi
+   \endgroup}
+
+\def\pack_layers_positioned_box_yes
+  {\vpack
+     {\vskip-\getboxlly\b_layers
+      \hskip-\getboxllx\b_layers
+      \hsize-\dimexpr\getboxllx\b_layers-\wd\b_layers\relax
+      \ifconditional\c_pack_layers_repeated\copy\else\box\fi\b_layers}}
+
+\def\pack_layers_positioned_box_nop
+  {\ifconditional\c_pack_layers_repeated\copy\else\box\fi\b_layers}
+
+% \definelayer[test][method=fit] \setupcolors[state=start,option=test]
+%
+% \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 when we use it as
+%D parameter. This name also suits better to other layering commands.
+
+\unexpanded\def\composedlayer#1{\flushlayer[#1]}
+
+\unexpanded\def\tightlayer[#1]%
+  {\hpack
+     {\def\currentlayer{#1}% todo: left/right
+      \setbox\nextbox\emptybox
+      \d_overlay_width \layerparameter\c!width
+      \d_overlay_height\layerparameter\c!height
+      \composedlayer{#1}}}
+
+\let\placelayer\flushlayer
+
+%D \macros
+%D  {setMPlayer}
+%D
+%D The following layer macro uses the positions that are 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
+
+\unexpanded\def\setMPlayer
+  {\dotripleempty\pack_layers_set_MP}
+
+\def\MPlayerwidth {\hsize}
+\def\MPlayerheight{\vsize}
+
+\def\pack_layers_set_MP[#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]}
+
+\unexpanded\def\getMPlayer
+  {\dodoubleempty\pack_layers_get_MP}
+
+\def\pack_layers_get_MP[#1][#2]%
+  {\framed[\c!background={\v!foreground,#1},\c!frame=\v!off,\c!offset=\v!overlay,#2]} % takes argument
+
+%D Watch out, a redefinition:
+
+\ifdefined\settextpagecontent \else
+    \writestatus\m!system{error in page-lyr.tex} \wait
+\fi
+
+\definelayer
+  [OTRTEXT]
+
+\setuplayer
+  [OTRTEXT]
+  [\c!width=\innermakeupwidth,
+   \c!height=\textheight]
+
+\let\normalsettextpagecontent\settextpagecontent % will be overloaded in page-spr
+
+\unexpanded\def\settextpagecontent#1#2#3% #2 and #3 will disappear
+  {\doifelselayerdata{OTRTEXT}
+     {\setbox#1\hpack 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