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+%D \module
+%D [ file=supp-mpe,
+%D version=1999.07.10,
+%D title=\CONTEXT\ Support Macros,
+%D subtitle=METAPOST Special Extensions,
+%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.
+
+%D This module is still experimental and deals with some
+%D extensions to \METAPOST. When using \POSTSCRIPT\ output,
+%D these extensions can be supplied by means of proper
+%D preamble definitions, but when producing \PDF\ we have to
+%D set up the appropriate datastructures ourselves. It acts as
+%D a plug in into \type {supp-pdf}. As soon as we need more
+%D extensions, we will generalize these macro.
+
+\writestatus{loading}{MetaPost Special Extensions}
+
+%D We implement extensions by using the \METAPOST\ special
+%D mechanism. Opposite to \TEX's specials, the \METAPOST\ ones
+%D are flushed before or after the graphic data, but thereby
+%D are no longer connected to a position.
+%D
+%D We implement specials by overloading the \type {fill}
+%D operator. By counting the fills, we can let the converter
+%D treat the appropriate fill in a special way. The
+%D specification of the speciality can have two forms,
+%D determined by the setting of a boolean variable:
+%D
+%D \starttypen
+%D _inline_shading_ := false ; % comment like code (default)
+%D _inline_shading_ := true ; % command like code
+%D \stoptypen
+%D
+%D When the specification is embedded as comment, it looks
+%D like:
+%D
+%D \starttypen
+%D %%MetaPostSpecial <size> <data> <number> <identifier>
+%D \stoptypen
+%D
+%D The in||line alternative is more tuned for \POSTSCRIPT,
+%D since it permits us to define a macro \type {special}.
+%D
+%D \starttypen
+%D inline : <data> <number> <identifier> <size> special
+%D \stoptypen
+%D
+%D The \type {identifier} determines what to do, and the data
+%D can be used to accomplish this. A type~2 shading function
+%D has identifier~2. Alltogether, the number of parameters is
+%D specified in \type {size}. The \type {number} is the number
+%D of the fill that needs the special treatment. For a type~2
+%D and~3 shaded fill, the datablock contains the following
+%D data:
+%D
+%D \starttypen
+%D from to n inner_r g b x y outer_r g b x y
+%D from to n inner_r g b x y radius outer_r g b x y radius
+%D \stoptypen
+%D
+%D The implementation below, saves the data on the stack in
+%D a way similar to the macros in \type {supp-pdf.tex}, and
+%D just overload a few already defined handlers. That way,
+%D the existing macros are still generic. \voetnoot {Actually,
+%D the macros here are just as generic.}
+%D
+%D Currently the only extension concerns shading, which is
+%D accomplished by handling yet another value of \type
+%D {\finiMPpath}. The recource disctionary is stored and
+%D later picked up by the general \CONTEXT\ figure inclusion
+%D macros.
+
+\unprotect
+
+\newcount\currentPDFshade % global count
+\newcount\currentMPshade % local count
+\newcount\currentMPfill % local count
+\chardef\inlineMPspecials=0 % only needed for stack resetting
+\let\currentMPshades\empty
+
+\def\dohandleMPspecialcomment#1
+ {\setMPargument{#1}%
+ \advance\scratchcounter by -1
+ \ifcase\scratchcounter
+ \handleMPspecialcommand
+ \donetrue
+ \doresetMPstack
+ \let\handleMPsequence=\dohandleMPsequence
+ \expandafter\handleMPsequence
+ \else
+ \expandafter\dohandleMPspecialcomment
+ \fi}
+
+\def\handleMPspecialcomment #1 % number of arguments
+ {\doresetMPstack
+ \scratchcounter=#1\relax
+ \ifcase\scratchcounter % when zero, inline shading is used
+ \chardef\inlineMPspecials=1
+ \let\handleMPsequence=\dohandleMPsequence
+ \expandafter\handleMPsequence
+ \else
+ \chardef\inlineMPspecials=0
+ \expandafter\dohandleMPspecialcomment
+ \fi}
+
+\def\startMPresources%
+ {\global\let\currentMPshades\empty
+ \global\currentMPfill=0
+ \global\currentMPshade=0
+ \ifx\currentPDFresources\empty\else
+ \message{unused resources before shade \the\currentPDFshade}%
+ \fi
+ \global\let\currentPDFresources\empty}
+
+\def\stopMPresources%
+ {\ifx\currentMPshades\empty
+ \global\let\currentPDFresources\empty
+ \else
+ \xdef\currentPDFresources%
+ {/Shading << \currentMPshades >>}%
+ \fi}
+
+\def\startMPshading#1%
+ {\edef\currentMPspecial{\gMPs{#1}}}
+
+\def\stopMPshading%
+ {\global\advance\currentPDFshade by 1
+ \global\advance\currentMPshade by 1
+ \setevalue{mps:Sh:\currentMPspecial}% non global !!
+ {\the\currentPDFshade}%
+ \xdef\currentMPshades%
+ {\currentMPshades/Sh\the\currentPDFshade\space\the\pdflastobj\space0 R }}
+
+\def\processMPpath%
+ {\global\advance\currentMPfill by 1
+ \ifnum\finiMPpath=2 \ifx\currentMPshades\empty \else
+ \doifdefined{mps:Sh:\the\currentMPfill}
+ {\chardef\finiMPpath=4 \PDFcode{q /Pattern cs}}%
+ \fi \fi
+ \flushMPpath
+ \closeMPpath
+ \PDFcode
+ {\ifcase\finiMPpath
+ W n\or S\or f\or B\or W n /Sh\getvalue{mps:Sh:\the\currentMPfill} sh Q%
+ \fi}%
+ \let\handleMPsequence=\dohandleMPsequence
+ \resetMPstack
+ \nofMPsegments=0
+ \handleMPsequence}
+
+\def\handleMPspecialcommand%
+ {\ifcase\inlineMPspecials\or
+ \advance\nofMParguments by -1 % pop the size
+ \fi
+ \doifundefinedelse{\MPspecial}
+ {\message{[unknown \MPspecial]}}
+ {\getvalue{\MPspecial}}%
+ \ifcase\inlineMPspecials
+ \doresetMPstack % 0
+ \else
+ \resetMPstack % 1
+ \fi}
+
+\def\MPspecial%
+ {MP special \gMPs\nofMParguments}
+
+\def\defineMPspecial#1#2%
+ {\setvalue{MP special #1}{#2}}
+
+%D Shading is an example of a more advanced graphic feature,
+%D but users will seldom encounter those complications. Here
+%D we only show a few simple examples, but many other
+%D alternatives are possible by setting up the functions built
+%D in \PDF\ in the appropriate way.
+%D
+%D Shading has to do with interpolation between two or more
+%D points or user supplied ranges. In \PDF, the specifications
+%D of a shade has to be encapsulated in objects and passed on
+%D as resources. This is a \PDF\ level 1.3. feature. One can
+%D simulate three dimensional shades as well and define simple
+%D functions using a limited set of \POSTSCRIPT\ primitives.
+%D Given the power of \METAPOST\ and these \PDF\ features, we
+%D can achieve superb graphic effects.
+%D
+%D Since everything is hidden in \TEX\ and \METAPOST\ graphics,
+%D we can stick to high level \CONTEXT\ command, as shown in
+%D the following exmples.
+%D
+%D \startbuffer
+%D \startuniqueMPgraphic{CircularShade}
+%D path p ; p := unitsquare xscaled \overlaywidth yscaled \overlayheight ;
+%D circular_shade(p,0,.2red,.9red) ;
+%D \stopuniqueMPgraphic
+%D
+%D \startuniqueMPgraphic{LinearShade}
+%D path p ; p := unitsquare xscaled \overlaywidth yscaled \overlayheight ;
+%D linear_shade(p,0,.2blue,.9blue) ;
+%D \stopuniqueMPgraphic
+%D
+%D \startuniqueMPgraphic{DuotoneShade}
+%D path p ; p := unitsquare xscaled \overlaywidth yscaled \overlayheight ;
+%D linear_shade(p,2,.5green,.5red) ;
+%D \stopuniqueMPgraphic
+%D \stopbuffer
+%D
+%D \typebuffer
+%D
+%D \haalbuffer
+%D
+%D These graphics can be hooked into the overlay mechanism,
+%D which is available in many commands.
+%D
+%D \startbuffer
+%D \defineoverlay[demo 1][\uniqueMPgraphic{CircularShade}]
+%D \defineoverlay[demo 2][\uniqueMPgraphic {LinearShade}]
+%D \defineoverlay[demo 3][\uniqueMPgraphic {DuotoneShade}]
+%D \stopbuffer
+%D
+%D \typebuffer
+%D
+%D \haalbuffer
+%D
+%D These backgrounds can for instance be applied to \type
+%D {\framed}:
+%D
+%D \startbuffer
+%D \setupframed[breedte=3cm,hoogte=2cm,kader=uit]
+%D \startcombinatie[3*1]
+%D {\framed[achtergrond=demo 1]{\bfd \white Demo 1}} {}
+%D {\framed[achtergrond=demo 2]{\bfd \white Demo 2}} {}
+%D {\framed[achtergrond=demo 3]{\bfd \white Demo 3}} {}
+%D \stopcombinatie
+%D \stopbuffer
+%D
+%D \typebuffer
+%D
+%D \startregelcorrectie
+%D \haalbuffer
+%D \stopregelcorrectie
+%D
+%D There are a few more alternatives, determined by the second
+%D parameter passed to \type {circular_shade} and alike.
+%D
+%D \def\SomeShade#1#2#3#4#5%
+%D {\startuniqueMPgraphic{Shade-#1}
+%D width := \overlaywidth ;
+%D height := \overlayheight ;
+%D path p ; p := unitsquare xscaled width yscaled height ;
+%D #2_shade(p,#3,#4,#5) ;
+%D \stopuniqueMPgraphic
+%D \defineoverlay[Shade-#1][\uniqueMPgraphic{Shade-#1}]%
+%D \framed[achtergrond=Shade-#1,breedte=2cm,hoogte=2cm,kader=uit]{}}
+%D
+%D \startregelcorrectie
+%D \startcombinatie[5*1]
+%D {\SomeShade{10}{circular}{0}{.3blue}{.9blue}} {circular 0}
+%D {\SomeShade{11}{circular}{1}{.3blue}{.9blue}} {circular 1}
+%D {\SomeShade{12}{circular}{2}{.3blue}{.9blue}} {circular 2}
+%D {\SomeShade{13}{circular}{3}{.3blue}{.9blue}} {circular 3}
+%D {\SomeShade{14}{circular}{4}{.3blue}{.9blue}} {circular 4}
+%D \stopcombinatie
+%D \stopregelcorrectie
+%D
+%D \blanko
+%D
+%D \startregelcorrectie
+%D \startcombinatie[5*1]
+%D {\SomeShade{20}{circular}{0}{.9green}{.3green}} {circular 0}
+%D {\SomeShade{21}{circular}{1}{.9green}{.3green}} {circular 1}
+%D {\SomeShade{22}{circular}{2}{.9green}{.3green}} {circular 2}
+%D {\SomeShade{23}{circular}{3}{.9green}{.3green}} {circular 3}
+%D {\SomeShade{24}{circular}{4}{.9green}{.3green}} {circular 4}
+%D \stopcombinatie
+%D \stopregelcorrectie
+%D
+%D \blanko
+%D
+%D \startregelcorrectie
+%D \startcombinatie[4*1]
+%D {\SomeShade{30}{linear}{0}{.3red}{.9red}} {linear 0}
+%D {\SomeShade{31}{linear}{1}{.3red}{.9red}} {linear 1}
+%D {\SomeShade{32}{linear}{2}{.3red}{.9red}} {linear 2}
+%D {\SomeShade{33}{linear}{3}{.3red}{.9red}} {linear 3}
+%D \stopcombinatie
+%D \stopregelcorrectie
+%D
+%D These macros closely cooperate with the \METAPOST\ module
+%D \type {mp-spec.mp}, which is part of the \CONTEXT\
+%D distribution.
+%D
+%D The low level (\PDF) implementation is based on the \TEX\
+%D based \METAPOST\ to \PDF\ converter. Shading is supported
+%D by overloading the \type {fill} operator as implemented
+%D earlier. In \PDF\ type~2 and~3 shading functions are
+%D specified in terms of:
+%D
+%D \starttabulatie[|Tl|l|]
+%D \NC /Domain \NC sort of meeting range \NC \NR
+%D \NC /C0 \NC inner shade \NC \NR
+%D \NC /C1 \NC outer shade \NC \NR
+%D \NC /N \NC smaller values, bigger inner circles \NC \NR
+%D \stoptabulatie
+
+\defineMPspecial{2}
+ {\startMPshading{14}% type 2
+ \immediate\pdfobj
+ {<</FunctionType 2
+ /Domain [\gMPs1 \gMPs2]
+ /C0 [\gMPs4 \gMPs5 \gMPs6]
+ /C1 [\gMPs9 \gMPs{10} \gMPs{11}]
+ /N \gMPs3>>}%
+ \immediate\pdfobj
+ {<</ShadingType 2
+ /ColorSpace /DeviceRGB
+ /Function \the\pdflastobj\space 0 R
+ /Coords [\gMPs7 \gMPs8 \gMPs{12} \gMPs{13}]
+ /Extend [true true]>>}%
+ \stopMPshading}
+
+\defineMPspecial{3}
+ {\startMPshading{16}% type 3
+ \immediate\pdfobj
+ {<</FunctionType 2
+ /Domain [\gMPs1 \gMPs2]
+ /C0 [\gMPs4 \gMPs5 \gMPs6]
+ /C1 [\gMPs{10} \gMPs{11} \gMPs{12}]
+ /N \gMPs3>>}%
+ \immediate\pdfobj
+ {<</ShadingType 3
+ /ColorSpace /DeviceRGB
+ /Function \the\pdflastobj\space 0 R
+ /Coords [\gMPs7 \gMPs8 \gMPs9 \gMPs{13} \gMPs{14} \gMPs{15}]
+ /Extend [true true]>>}%
+ \stopMPshading}
+
+\protect \endinput
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