GNU libunistring: 12. Line breaking <unilbrk.h>

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# 12. Line breaking `<unilbrk.h>`

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 encoding argument identifies the encoding (e.g. `"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 s as an array `s[0..n-1]` and a position i, the values have the following meanings:

Constant: int UC_BREAK_MANDATORY

  This value indicates that `s[i]` is a line break character.

Constant: int UC_BREAK_CR_BEFORE_LF

  This value is a variant of `UC_BREAK_MANDATORY`. It indicates that `s[i]` is a CR character and that `s[i+1]` is a LF character.

Constant: int UC_BREAK_POSSIBLE

  This value indicates that a line break may be inserted between `s[i-1]` and `s[i]`.

Constant: int UC_BREAK_HYPHENATION

  This value indicates that a hyphen and a line break may be inserted between `s[i-1]` and `s[i]`. But beware of language dependent hyphenation rules.

Constant: int UC_BREAK_PROHIBITED

  This value indicates that `s[i-1]` and `s[i]` must not be separated.

Constant: int UC_BREAK_UNDEFINED

  This value is not used as a return value; rather, in the overriding argument of the `u*_width_linebreaks` functions, it indicates the absence of an override.

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

Function: void u8_possible_linebreaks (const uint8_t *s, size_t n, const char *encoding, char *p)
Function: void u16_possible_linebreaks (const uint16_t *s, size_t n, const char *encoding, char *p)
Function: void u32_possible_linebreaks (const uint32_t *s, size_t n, const char *encoding, char *p)
Function: void ulc_possible_linebreaks (const char *s, size_t n, const char *encoding, char *p)

  Determines the line break points in s, and stores the result at `p[0..n-1]`. Every `p[i]` is assigned one of the values `UC_BREAK_MANDATORY`, `UC_BREAK_CR_BEFORE_LF`, `UC_BREAK_POSSIBLE`, `UC_BREAK_HYPHENATION`, `UC_BREAK_PROHIBITED`.

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.

Function: int u8_width_linebreaks (const uint8_t *s, size_t n, int width, int start_column, int at_end_columns, const char *override, const char *encoding, char *p)
Function: int u16_width_linebreaks (const uint16_t *s, size_t n, int width, int start_column, int at_end_columns, const char *override, const char *encoding, char *p)
Function: int u32_width_linebreaks (const uint32_t *s, size_t n, int width, int start_column, int at_end_columns, const char *override, const char *encoding, char *p)
Function: int ulc_width_linebreaks (const char *s, size_t n, int width, int start_column, int at_end_columns, const char *override, const char *encoding, char *p)

  Chooses the best line breaks, assuming that every character occupies a width given by the `uc_width` function (see Display width `<uniwidth.h>`).

  The string is `s[0..n-1]`.

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

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

  The given encoding is used for disambiguating widths in `uc_width`.

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

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