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, char32_t c);

int unicode_lb_next_cnt(unicode_lb_info_t lb, const char32_t *cptr, size_t cnt);

int unicode_lb_end(unicode_lb_info_t lb);

unicode_lbc_info_t unicode_lbc_init( int (*cb_func)(int, char32_t, 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, char32_t c);

int unicode_lbc_next_cnt(unicode_lb_info_t lb, const char32_t *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 After the call to unicode_lb_end() the line breaking unicode_lb_info_t handle is no longer valid.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

UNICODE_LB_NONE

UNICODE_LB_ALLOWED

The callback function should return 0. A non-zero value indicates to the line breaking algorithm that an error has occurred. 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.

			PR x PR
			AL x PR
		        ID x PR

			SY x EX
			SY x AL
			SY x ID
		        SP ÷ SY, which takes precedence over "x SY".

SEE ALSO¶

courier-unicode(7), unicode::linebreak(3), TR-14[1]

AUTHOR¶

Sam Varshavchik

NOTES¶

1.

TR-14