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1%D \module
2%D   [       file=page-fac,   % moved from page-ini
3%D        version=2011.12.07, % 2000.10.20,
4%D          title=\CONTEXT\ Page Macros,
5%D       subtitle=Facing Pages,
6%D         author=Hans Hagen,
7%D           date=\currentdate,
8%D      copyright={PRAGMA ADE \& \CONTEXT\ Development Team}]
9%C
10%C This module is part of the \CONTEXT\ macro||package and is
11%C therefore copyrighted by \PRAGMA. See mreadme.pdf for
12%C details.
13
14\writestatus{loading}{ConTeXt Page Macros / Facing Pages}
15
16\unprotect
17
18%D \macros
19%D   {setupoppositeplacing,startopposite}
20%D
21%D \starttyping
22%D \starttext
23%D test \startopposite \blackrule[width=3cm,height=4cm] \stopopposite test
24%D test \startopposite \blackrule[width=3cm,height=4cm] \stopopposite test
25%D \stoptext
26%D \stoptyping
27
28\newbox        \b_page_facings_content
29\newconditional\c_page_facings_busy
30
31\installcorenamespace{oppositeplacing}
32
33\installsetuponlycommandhandler \??oppositeplacing {oppositeplacing}
34
35\unexpanded\def\startopposite
36  {\dowithnextboxcontent
37     {\hsize\makeupwidth}%
38     {\global\setbox\b_page_facings_content\vbox
39        {\ifvoid\b_page_facings_content
40           \directoppositeplacingparameter\c!before
41         \else
42           \directoppositeplacingparameter\c!inbetween
43           \unvbox\b_page_facings_content
44         \fi
45         \box\nextbox}}%
46     \vbox\bgroup}
47
48\unexpanded\def\stopopposite
49  {\egroup}
50
51\def\page_facings_finish
52  {\ifvoid\b_page_facings_content \else
53     \global\setbox\b_page_facings_content\vbox to \makeupheight
54       {\unvbox\b_page_facings_content
55        \directoppositeplacingparameter\c!after
56        \vss}%
57   \fi}
58
59\def\page_facings_flush
60  {\ifconditional\c_page_facings_busy
61     \ifvoid\b_page_facings_content \else
62        \page_facings_flush_indeed
63     \fi
64   \fi}
65
66\def\page_facings_flush_indeed
67  {\ifnum\realpageno>\plusone
68     \begingroup
69     \pageornamentstate\plusone % tricky
70     \page_facings_finish
71     \page_boxes_shipout{\page_boxes_constructed_page\box\b_page_facings_content}%
72     \endgroup
73   \else
74     \global\setbox\b_page_facings_content\emptybox
75   \fi}
76
77\appendtoks
78    \doifelse{\directoppositeplacingparameter\c!state}\v!start\settrue\setfalse\c_page_facings_busy
79\to \everysetupoppositeplacing
80
81\setupoppositeplacing
82  [\c!state=\v!start,
83   \c!before=,
84   \c!inbetween=\blank,
85   \c!after=]
86
87\protect \endinput
88