1UNICODE_LINE_BREAK(3) Courier Unicode Library UNICODE_LINE_BREAK(3)
2
6 unicode_line_break, unicode_lb_init, unicode_lb_set_opts,
7 unicode_lb_next, unicode_lb_next_cnt, unicode_lb_end, unicode_lbc_init,
8 unicode_lbc_set_opts, unicode_lbc_next, unicode_lbc_next_cnt,
9 unicode_lbc_end - calculate mandatory or allowed line breaks
10
12 #include <courier-unicode.h>
13 unicode_lb_info_t unicode_lb_init(int (*cb_func)(int, void *),
15 void *cb_arg);
16 void unicode_lb_set_opts(unicode_lb_info_t lb, int opts);
18 int unicode_lb_next(unicode_lb_info_t lb, char32_t c);
20 int unicode_lb_next_cnt(unicode_lb_info_t lb, const char32_t *cptr,
22 size_t cnt);
23 int unicode_lb_end(unicode_lb_info_t lb);
25 unicode_lbc_info_t
27 unicode_lbc_init(int (*cb_func)(int, char32_t, void *),
28 void *cb_arg);
29 void unicode_lbc_set_opts(unicode_lbc_info_t lb, int opts);
31 int unicode_lbc_next(unicode_lb_info_t lb, char32_t c);
33 int unicode_lbc_next_cnt(unicode_lb_info_t lb, const char32_t *cptr,
35 size_t cnt);
36 int unicode_lbc_end(unicode_lb_info_t lb);
38
40 These functions implement the unicode line breaking algorithm. Invoke
41 unicode_lb_init() to initialize the line breaking algorithm. The first
42 parameter is a callback function. The second parameter is an opaque
43 pointer. The callback function gets invoked with two parameters. The
44 first parameter is one of three values: UNICODE_LB_MANDATORY,
45 UNICODE_LB_NONE, or UNICODE_LB_ALLOWED, as described below. The second
46 parameter is the opaque pointer that was passed to unicode_lb_init();
47 the opaque pointer is not subject to any further interpretation by
48 these functions.
49 unicode_lb_init() returns an opaque handle. Repeated invocations of
51 unicode_lb_next(), passing the handle and one unicode character at a
52 time, defines a sequence of unicode characters over which the line
53 breaking algorithm calculation takes place. unicode_lb_next_cnt() is a
54 shortcut for invoking unicode_lb_next() repeatedly over an array cptr
55 containing cnt unicode characters.
56 unicode_lb_end() denotes the end of the unicode character sequence.
58 After the call to unicode_lb_end() the line breaking unicode_lb_info_t
59 handle is no longer valid.
60 Between the call to unicode_lb_init() and unicode_lb_end(), the
62 callback function gets invoked exactly once for each unicode character
63 given to unicode_lb_next() or unicode_lb_next_cnt(). Usually each call
64 to unicode_lb_next() results in the callback function getting invoked
65 immediately, but it does not have to be. It's possible that a call to
66 unicode_lb_next() returns without invoking the callback function, and
67 some subsequent call to unicode_lb_next() (or unicode_lb_end()) invokes
68 the callback function more than once, to catch up. The contract is that
69 before unicode_lb_end() returns, the callback function gets invoked the
70 exact number of times as the number of characters in the unicode
71 sequence defined by the intervening calls to unicode_lb_next() and
72 unicode_lb_next_cnt(), unless an error occurs.
73 Each call to the callback function reports the calculated line breaking
75 status of the corresponding character in the unicode character
76 sequence:
77 UNICODE_LB_MANDATORY
79 A line break is MANDATORY before the corresponding character.
80 UNICODE_LB_NONE
82 A line break is PROHIBITED before the corresponding character.
83 UNICODE_LB_ALLOWED
85 A line break is OPTIONAL before the corresponding character.
86 The callback function should return 0. A non-zero value indicates to
88 the line breaking algorithm that an error has occurred.
89 unicode_lb_next() and unicode_lb_next_cnt() return zero either if they
90 never invoked the callback function, or if each call to the callback
91 function returned zero. A non zero return from the callback function
92 results in unicode_lb_next() and unicode_lb_next_cnt() immediately
93 returning the same value.
94 unicode_lb_end() must be invoked to destroy the line breaking handle
96 even if unicode_lb_next() and unicode_lb_next_cnt() returned an error
97 indication. It's also possible that, under normal circumstances,
98 unicode_lb_end() invokes the callback function one or more times. The
99 return value from unicode_lb_end() has the same meaning as from
100 unicode_lb_next() and unicode_lb_next_cnt(); however in all cases after
101 unicode_lb_end() returns the line breaking handle is no longer valid.
102 Alternative callback function
104 unicode_lbc_init(), unicode_lbc_next(), unicode_lbc_next_cnt(),
105 unicode_lbc_end() are alternative functions that implement the same
106 algorithm. The only difference is that the callback function receives
107 an extra parameter, the unicode character value to which the line
108 breaking status applies to, passed through from the input unicode
109 character sequence.
110 Options
112 unicode_lb_set_opts() and unicode_lbc_set_opts() enable non-default
113 options for the line breaking algorithm. These functions must be called
114 immediately after unicode_lb_init() or unicode_lbc_init(), and before
115 any other function. opts is a bitmask that can contain the following
116 values:
117 UNICODE_LB_OPT_PRBREAK
119 Enables a modified LB24 rule. This prevents plus signs, as in “C++”
120 from breaking. This flag adds the following rules to the LB24 rule:
121 PR x PR
123 AL x PR
125 ID x PR
127 UNICODE_LB_OPT_SYBREAK
129 Tailored breaking rules for the “/” character. This prevents
130 breaking after the “/” character (think URLs); including an
131 exception to the “x SY” rule in LB13. This flag adds the following
132 rules to the LB24 rule:
133 SY x EX
135 SY x AL
137 SY x ID
139 SP ÷ SY, which takes precedence over "x SY".
141 UNICODE_LB_OPT_DASHWJ
143 This flag reclassifies U+2013 and U+2014 as class WJ, prohibiting
144 breaks before and after the m-dash and the n-dash unicode
145 characters.
146
148 courier-unicode(7), unicode::linebreak(3), TR-14[1]
149
151 Sam Varshavchik
152 Author
153
155 1. TR-14
156 https://www.unicode.org/reports/tr14/tr14-45.html
157Courier Unicode Library 05/31/2022 UNICODE_LINE_BREAK(3)