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UNICODE_LINE_BREAK(3) Courier Unicode Library UNICODE_LINE_BREAK(3)
NAME
unicode_lb_init, unicode_lb_set_opts, unicode_lb_next,
unicode_lb_next_cnt, unicode_lb_end, unicode_lbc_init,
unicode_lbc_set_opts, unicode_lbc_next, unicode_lbc_next_cnt,
unicode_lbc_end - calculate mandatory or allowed line breaks
SYNOPSIS
#include <courier-unicode.h>
unicode_lb_info_t unicode_lb_init(int (*cb_func)(int, void *),
void *cb_arg);
void unicode_lb_set_opts(unicode_lb_info_t lb, int opts);
int unicode_lb_next(unicode_lb_info_t lb, unicode_char c);
int unicode_lb_next_cnt(unicode_lb_info_t lb, const unicode_char *cptr,
size_t cnt);
int unicode_lb_end(unicode_lb_info_t lb);
unicode_lbc_info_t
unicode_lbc_init(int
(*cb_func)(int, unicode_char,
void *), void *cb_arg);
void unicode_lbc_set_opts(unicode_lbc_info_t lb, int opts);
int unicode_lbc_next(unicode_lb_info_t lb, unicode_char c);
int unicode_lbc_next_cnt(unicode_lb_info_t lb,
const unicode_char *cptr, size_t cnt);
int unicode_lbc_end(unicode_lb_info_t lb);
DESCRIPTION
These functions implement the unicode line breaking algorithm. Invoke
unicode_lb_init() to initialize the line breaking algorithm. The first
parameter is a callback function. The second parameter is an opaque
pointer. The callback function gets invoked with two parameters. The
first parameter is one of three values: UNICODE_LB_MANDATORY,
UNICODE_LB_NONE, or UNICODE_LB_ALLOWED, as described below. The second
parameter is the opaque pointer that was passed to unicode_lb_init();
the opaque pointer is not subject to any further interpretation by
these functions.
unicode_lb_init() returns an opaque handle. Repeated invocations of
unicode_lb_next(), passing the handle and one unicode character at a
time, defines a sequence of unicode characters over which the line
breaking algorithm calculation takes place. unicode_lb_next_cnt() is a
shortcut for invoking unicode_lb_next() repeatedly over an array cptr
containing cnt unicode characters.
unicode_lb_end() denotes the end of the unicode character sequence.
After the call to unicode_lb_end() the line breaking unicode_lb_info_t
handle is no longer valid.
Between the call to unicode_lb_init() and unicode_lb_end(), the
callback function gets invoked exactly once for each unicode character
given to unicode_lb_next() or unicode_lb_next_cnt(). Usually each call
to unicode_lb_next() results in the callback function getting invoked
immediately, but it does not have to be. It's possible that a call to
unicode_lb_next() returns without invoking the callback function, and
some subsequent call to unicode_lb_next() (or unicode_lb_end()) invokes
the callback function more than once, to catch up. The contract is that
before unicode_lb_end() returns, the callback function gets invoked the
exact number of times as the number of characters in the unicode
sequence defined by the intervening calls to unicode_lb_next() and
unicode_lb_next_cnt(), unless an error occurs.
Each call to the callback function reports the calculated line breaking
status of the corresponding character in the unicode character
sequence:
UNICODE_LB_MANDATORY
A line break is MANDATORY before the corresponding character.
UNICODE_LB_NONE
A line break is PROHIBITED before the corresponding character.
UNICODE_LB_ALLOWED
A line break is OPTIONAL before the corresponding character.
The callback function should return 0. A non-zero value indicates to
the line breaking algorithm that an error has occured.
unicode_lb_next() and unicode_lb_next_cnt() return zero either if they
never invoked the callback function, or if each call to the callback
function returned zero. A non zero return from the callback function
results in unicode_lb_next() and unicode_lb_next_cnt() immediately
returning the same value.
unicode_lb_end() must be invoked to destroy the line breaking handle
even if unicode_lb_next() and unicode_lb_next_cnt() returned an error
indication. It's also possible that, under normal circumstances,
unicode_lb_end() invokes the callback function one or more times. The
return value from unicode_lb_end() has the same meaning as from
unicode_lb_next() and unicode_lb_next_cnt(); however in all cases after
unicode_lb_end() returns the line breaking handle is no longer valid.
Alternative callback function
unicode_lbc_init(), unicode_lbc_next(), unicode_lbc_next_cnt(),
unicode_lbc_end() are alternative functions that implement the same
algorithm. The only difference is that the callback function receives
an extra parameter, the unicode character value to which the line
breaking status applies to, passed through from the input unicode
character sequence.
Options
unicode_lb_set_opts() and unicode_lbc_set_opts() enable non-default
options for the line breaking algorithm. These functions must be called
immediately after unicode_lb_init() or unicode_lbc_init(), and before
any other function. opts is a bitmask that can contain the following
values:
UNICODE_LB_OPT_PRBREAK
Enables a modified LB24 rule. This prevents plus signs, as in "C++"
from breaking. This flag adds the following rules to the LB24 rule:
PR x PR
AL x PR
ID x PR
UNICODE_LB_OPT_SYBREAK
Tailored breaking rules for the "/" character. This prevents
breaking after the "/" character (think URLs); including an
exception to the "x SY" rule in LB13. This flag adds the following
rules to the LB24 rule:
SY x EX
SY x AL
SY x ID
SP / SY, which takes precedence over "x SY".
UNICODE_LB_OPT_DASHWJ
This flag reclassifies U+2013 and U+2014 as class WJ, prohibiting
breaks before and after the m-dash and the n-dash unicode
characters.
SEE ALSO
courier-unicode(7), unicode::linebreak(3), TR-14[1]
AUTHOR
Sam Varshavchik
Author
NOTES
1. TR-14
http://www.unicode.org/reports/tr14/tr14-35.html
Courier Unicode Library 07/29/2015 UNICODE_LINE_BREAK(3)