@node unilbrk.h
@chapter Line breaking @code{<unilbrk.h>}

@cindex line breaks
@cindex breaks, line
@cindex wrapping
This include file declares functions for determining where in a string
line breaks could or should be introduced, in order to make the displayed
string fit into a column of given width.

These functions are locale dependent.  The @var{encoding} argument identifies
the encoding (e.g@. @code{"ISO-8859-2"} for Polish).

The following enumerated values indicate whether, at a given position, a line
break is possible or not.  Given an string @var{s} as an array
@code{@var{s}[0..@var{n}-1]} and a position @var{i}, the values have the
following meanings:

@deftypevr Constant int UC_BREAK_MANDATORY
This value indicates that @code{@var{s}[@var{i}]} is a line break character.
@end deftypevr

@deftypevr Constant int UC_BREAK_POSSIBLE
This value indicates that a line break may be inserted between
@code{@var{s}[@var{i}-1]} and @code{@var{s}[@var{i}]}.
@end deftypevr

@deftypevr Constant int UC_BREAK_HYPHENATION
This value indicates that a hyphen and a line break may be inserted between
@code{@var{s}[@var{i}-1]} and @code{@var{s}[@var{i}]}.  But beware of language
dependent hyphenation rules.
@end deftypevr

@deftypevr Constant int UC_BREAK_PROHIBITED
This value indicates that @code{@var{s}[@var{i}-1]} and @code{@var{s}[@var{i}]}
must not be separated.
@end deftypevr

@deftypevr Constant int UC_BREAK_UNDEFINED
This value is not used as a return value; rather, in the overriding argument of
the @code{u*_width_linebreaks} functions, it indicates the absence of an
override.
@end deftypevr

The following functions determine the positions at which line breaks are
possible.

@deftypefun void u8_possible_linebreaks (const@tie{}uint8_t@tie{}*@var{s}, size_t@tie{}@var{n}, const@tie{}char@tie{}*@var{encoding}, char@tie{}*@var{p})
@deftypefunx void u16_possible_linebreaks (const@tie{}uint16_t@tie{}*@var{s}, size_t@tie{}@var{n}, const@tie{}char@tie{}*@var{encoding}, char@tie{}*@var{p})
@deftypefunx void u32_possible_linebreaks (const@tie{}uint32_t@tie{}*@var{s}, size_t@tie{}@var{n}, const@tie{}char@tie{}*@var{encoding}, char@tie{}*@var{p})
@deftypefunx void ulc_possible_linebreaks (const@tie{}char@tie{}*@var{s}, size_t@tie{}@var{n}, const@tie{}char@tie{}*@var{encoding}, char@tie{}*@var{p})
Determines the line break points in @var{s}, and stores the result at
@code{@var{p}[0..@var{n}-1]}.  Every @code{@var{p}[@var{i}]} is assigned one of
the values @code{UC_BREAK_MANDATORY}, @code{UC_BREAK_POSSIBLE},
@code{UC_BREAK_HYPHENATION}, @code{UC_BREAK_PROHIBITED}.
@end deftypefun

The following functions determine where line breaks should be inserted so that
each line fits in a given width, when output to a device that uses
non-proportional fonts.

@deftypefun int u8_width_linebreaks (const@tie{}uint8_t@tie{}*@var{s}, size_t@tie{}@var{n}, int@tie{}@var{width}, int@tie{}@var{start_column}, int@tie{}@var{at_end_columns}, const@tie{}char@tie{}*@var{override}, const@tie{}char@tie{}*@var{encoding}, char@tie{}*@var{p})
@deftypefunx int u16_width_linebreaks (const@tie{}uint16_t@tie{}*@var{s}, size_t@tie{}@var{n}, int@tie{}@var{width}, int@tie{}@var{start_column}, int@tie{}@var{at_end_columns}, const@tie{}char@tie{}*@var{override}, const@tie{}char@tie{}*@var{encoding}, char@tie{}*@var{p})
@deftypefunx int u32_width_linebreaks (const@tie{}uint32_t@tie{}*@var{s}, size_t@tie{}@var{n}, int@tie{}@var{width}, int@tie{}@var{start_column}, int@tie{}@var{at_end_columns}, const@tie{}char@tie{}*@var{override}, const@tie{}char@tie{}*@var{encoding}, char@tie{}*@var{p})
@deftypefunx int ulc_width_linebreaks (const@tie{}char@tie{}*@var{s}, size_t@tie{}@var{n}, int@tie{}@var{width}, int@tie{}@var{start_column}, int@tie{}@var{at_end_columns}, const@tie{}char@tie{}*@var{override}, const@tie{}char@tie{}*@var{encoding}, char@tie{}*@var{p})
Chooses the best line breaks, assuming that every character occupies a width
given by the @code{uc_width} function (see @ref{uniwidth.h}).

The string is @code{@var{s}[0..@var{n}-1]}.

The maximum number of columns per line is given as @var{width}.
The starting column of the string is given as @var{start_column}.
If the algorithm shall keep room after the last piece, this amount of room can
be given as @var{at_end_columns}.

@var{override} is an optional override; if
@code{@var{override}[@var{i}] != UC_BREAK_UNDEFINED},
@code{@var{override}[@var{i}]} takes precedence over @code{@var{p}[@var{i}]}
as returned by the @code{u*_possible_linebreaks} function.

The given @var{encoding} is used for disambiguating widths in @code{uc_width}.

Returns the column after the end of the string, and stores the result at
@code{@var{p}[0..@var{n}-1]}.  Every @code{@var{p}[@var{i}]} is assigned one of
the values @code{UC_BREAK_MANDATORY}, @code{UC_BREAK_POSSIBLE},
@code{UC_BREAK_HYPHENATION}, @code{UC_BREAK_PROHIBITED}.  Here the value
@code{UC_BREAK_POSSIBLE} indicates that a line break @emph{should} be inserted.
@end deftypefun