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1%D \module
2%D   [       file=spac-pag,
3%D        version=2009.10.16, % 1997.03.31, was core-spa.tex
4%D          title=\CONTEXT\ Spacing Macros,
5%D       subtitle=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 Spacing Macros / Pages}
15
16\unprotect
17
18%D The code here has evolved over time and might not be the best
19%D around. Maybe much will be gone a some point.
20
21\installcorenamespace {alignswitch}
22
23\letvalue{\??alignswitch\v!left  }\zerocount
24\letvalue{\??alignswitch\v!middle}\plusone
25\letvalue{\??alignswitch\v!right }\plustwo
26
27\def\setalignmentswitch#1%
28  {\chardef\alignmentswitch\csname\??alignswitch\ifcsname\??alignswitch#1\endcsname#1\else\v!left\fi\endcsname}
29
30\newif      \ifpagestatemismatch
31\newcount   \realpagestateno
32\newconstant\frozenpagestate
33
34\def\dotrackpagestate#1#2%
35  {\ifdoublesided \ifinpagebody \else
36     \doforcedtrackpagestate{#1}{#2}%
37   \fi \fi}
38
39\def\doforcedtrackpagestate#1#2%
40  {\ifcase\frozenpagestate
41     \global\advance#2\plusone
42     \setpagestate[#1][\number#2]%
43   \fi}
44
45\let\m_spac_pagestates_realpage\empty
46
47\newconditional\c_spac_pagestates_found
48
49\unexpanded\def\docheckpagestate#1#2%
50  {\ifcase\frozenpagestate
51     \setpagestaterealpageno{#1}{\number#2}%
52   \fi}
53
54\unexpanded\def\doifelserightpagestate#1#2% not expandable !
55  {\ifcase\frozenpagestate
56     \pagestatemismatchfalse
57     \realpagestateno\realfolio
58     \ifinpagebody
59       \ifdoublesided
60         \ifodd\realpageno\relax
61           \settrue\c_spac_pagestates_found
62         \else
63           \setfalse\c_spac_pagestates_found
64         \fi
65       \else
66         \settrue\c_spac_pagestates_found
67       \fi
68     \else\ifdoublesided
69       \edef\m_spac_pagestates_realpage{\pagestaterealpage{#1}{\number#2}}%
70       \ifx\m_spac_pagestates_realpage\empty
71         \ifodd\realpageno\relax
72           \settrue\c_spac_pagestates_found
73         \else
74           \setfalse\c_spac_pagestates_found
75         \fi
76       \else
77         \realpagestateno\m_spac_pagestates_realpage\relax
78         \ifnum\realpagestateno=\realpageno \else
79           \pagestatemismatchtrue
80         \fi
81         \ifodd\realpagestateno\relax
82           \settrue\c_spac_pagestates_found
83         \else
84           \setfalse\c_spac_pagestates_found
85         \fi
86       \fi
87     \else
88       \settrue\c_spac_pagestates_found
89     \fi\fi
90   \else
91     \ifodd\realpagestateno\relax
92       \settrue\c_spac_pagestates_found
93     \else
94       \setfalse\c_spac_pagestates_found
95     \fi
96   \fi
97   \ifconditional\c_spac_pagestates_found
98     \expandafter\firstoftwoarguments
99   \else
100     \expandafter\secondoftwoarguments
101   \fi}
102
103\unexpanded\def\doifelseforcedrightpagestate#1#2%
104  {\ifcase\frozenpagestate
105     \pagestatemismatchfalse
106     \realpagestateno\realfolio
107     \edef\m_spac_pagestates_realpage{\pagestaterealpage{#1}{\number#2}}%
108     \ifx\m_spac_pagestates_realpage\empty
109       \ifodd\realpageno\relax
110         \settrue\c_spac_pagestates_found
111       \else
112         \setfalse\c_spac_pagestates_found
113       \fi
114     \else
115       \realpagestateno\m_spac_pagestates_realpage\relax
116       \ifnum\realpagestateno=\realpageno \else
117         \pagestatemismatchtrue
118       \fi
119       \ifodd\realpagestateno\relax
120         \settrue\c_spac_pagestates_found
121       \else
122         \setfalse\c_spac_pagestates_found
123       \fi
124     \fi
125   \else
126     \ifodd\realpagestateno\relax
127       \settrue\c_spac_pagestates_found
128     \else
129       \setfalse\c_spac_pagestates_found
130     \fi
131   \fi
132   \ifconditional\c_spac_pagestates_found
133     \expandafter\firstoftwoarguments
134   \else
135     \expandafter\secondoftwoarguments
136   \fi}
137
138\let\doifrightpagestateelse      \doifelserightpagestate
139\let\doifforcedrightpagestateelse\doifelseforcedrightpagestate
140
141\unexpanded\def\freezepagestate {\frozenpagestate\plusone  }
142\unexpanded\def\defrostpagestate{\frozenpagestate\zerocount}
143
144% we can make more of these on top, but how to deal with mixed frozen states
145
146% \dorecurse{500}{\dontleavehmode\signalrightpage\doifrightpageelse{right}{left}\par} % given doublesided
147
148\newcount\nofraggedparagraphs
149
150\definepagestate[\s!paragraph]
151
152\unexpanded\def\signalrightpage  {\dotrackpagestate      \s!paragraph\nofraggedparagraphs} % use \dontleavehmode if needed
153\unexpanded\def\doifelserightpage{\doifelserightpagestate\s!paragraph\nofraggedparagraphs}
154\unexpanded\def\rightpageorder   {\pagestaterealpageorder\s!paragraph\nofraggedparagraphs}
155
156\let\doifrightpageelse\doifelserightpage
157
158\installcorenamespace{pagechanges}
159
160\newif\ifpagechanged \let\lastchangedpage\empty
161
162\def\spac_pagechanges_check#1#2#3%
163  {\pagechangedfalse
164   \doforcedtrackpagestate{#2}{#3}%
165   \edef\m_spac_pagestates_realpage{\pagestaterealpage{#2}{\number#3}}%
166   \ifx\m_spac_pagestates_realpage\empty \else
167     \ifnum\m_spac_pagestates_realpage>0\csname\??pagechanges#2:#1\endcsname\relax
168       \pagechangedtrue
169     \fi
170   \fi
171   \ifpagechanged
172     \letgvalue{\??pagechanges#2:#1}\m_spac_pagestates_realpage
173     \glet\lastchangedpage\m_spac_pagestates_realpage
174   \else
175     \glet\lastchangedpage\realfolio
176   \fi}
177
178\def\changedpagestate#1#2%
179  {\executeifdefined{\??pagechanges#2:#1}0}
180
181\def\checkpagechange#1{\spac_pagechanges_check{#1}\s!paragraph\nofraggedparagraphs}
182\def\changedpage    #1{\changedpagestate{#1}\s!paragraph}
183
184\protect \endinput
185