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UNICODE::BIDI(3) Courier Unicode Library UNICODE::BIDI(3) NAME unicode::bidi, unicode::bidi_calc, unicode::bidi_calc_types, uni- code::bidi_reorder, unicode::bidi_cleanup, unicode::bidi_logical_order, unicode::bidi_combinings, unicode::bidi_needs_embed, unicode::bidi_embed, unicode::bidi_embed_paragraph_level, unicode::bidi_get_direction, uni- code::bidi_override - unicode bi-directional algorithm SYNOPSIS #include <courier-unicode.h> struct unicode::bidi_calc_types { bidi_calc_types(const std::u32string & string); std::vector<unicode_bidi_type_t> types ; void setbnl(std::u32string & string); }.fi std::tuple<std::vector<unicode_bidi_level_t>, struct unicode_bidi_direction> unicode::bidi_calc(const unicode::bidi_calc_types &ustring); std::tuple<std::vector<unicode_bidi_level_t>, struct unicode_bidi_direction> unicode::bidi_calc(const unicode::bidi_calc_types &ustring, unicode_bidi_level_t embedding_level); int unicode::bidi_reorder(std::u32string &string, std::vector<unicode_bidi_level_t> &embedding_level, const std::function<void (size_t, size_t)> &reorder_callback=[](size_t, size_t){}, size_t starting_pos=0, size_t n=(size_t)-1); void unicode::bidi_reorder(std::vector<unicode_bidi_level_t> &embedding_level, const std::function<void (size_t, size_t)> &reorder_callback=[](size_t, size_t){}, size_t starting_pos=0, size_t n=(size_t)-1); void unicode::bidi_cleanup(std::u32string &string, const std::function<void (size_t)> &removed_callback=[](size_t){}, int cleanup_options); int unicode::bidi_cleanup(std::u32string &string, std::vector <unicode_bidi_level_t> &levels, const std::function<void (size_t)> &removed_callback=[](size_t){}, int cleanup_options=0); int unicode::bidi_cleanup(std::u32string &string, std::vector <unicode_bidi_level_t> &levels, const std::function<void (size_t)> &removed_callback, int cleanup_options, size_t starting_pos, size_t n); int unicode::bidi_logical_order(std::u32string &string, std::vector <unicode_bidi_level_t> &levels, unicode_bidi_level_t paragraph_embedding, const std::function<void (size_t, size_t)> &reorder_callback=[](size_t, size_t){}, size_t starting_pos=0, size_t n=(size_t)-1); void unicode::bidi_combinings(const std::u32string_view &string, const std::vector <unicode_bidi_level_t> &levels, const std::function <void (unicode_bidi_level_t level, size_t level_start, size_t n_chars, size_t comb_start, size_t n_comb_chars)> &callback); void unicode::bidi_combinings(const std::u32string_view &string, const std::function <void (unicode_bidi_level_t level, size_t level_start, size_t n_chars, size_t comb_start, size_t n_comb_chars)> &callback); void unicode::bidi_logical_order(std::vector <unicode_bidi_level_t> &levels, unicode_bidi_level_t paragraph_embedding, const std::function<void (size_t, size_t)> &reorder_callback, size_t starting_pos=0, size_t n=(size_t)-1); bool unicode::bidi_needs_embed(const std::u32string_view &string, const std::vector <unicode_bidi_level_t> &levels, const unicode_bidi_level_t (paragraph_embedding=NULL, size_t starting_pos=0, size_t n=(size_t)-1); int unicode::bidi_embed(const std::u32string_new &string, const std::vector <unicode_bidi_level_t> &levels, unicode_bidi_level_t paragraph_embedding, const std::function<void (const char32_t *, size_t, bool)> &callback); std::u32string unicode::bidi_embed(const std::u32string &string, const std::vector <unicode_bidi_level_t> &levels, unicode_bidi_level_t paragraph_embedding); char32_t unicode::bidi_embed_paragraph_level(const std::u32string_view &string, unicode_bidi_level_t paragraph_embedding); unicode_bidi_direction bidi_get_direction(const std::u32string_view &string, size_t starting_pos=0, size_t n=(size_t)-1); std::u32string bidi_override(const std::u32string_view &string, unicode_bidi_level_t direction, int cleanup_options=0); DESCRIPTION These functions implement the C++ interface for the Unicode Bi-Directional algorithm[1]. See the description of the underlying unicode_bidi(3) C li- brary API for more information. C++ specific notes: * unicode::bidi_calc returns the directional embedding value buffer and the calculated paragraph embedding level. Its ustring is implicitly converted from a std::u32string: std::u32string text; auto [levels, direction]=unicode::bidi_calc(text); Alternatively a unicode::bidi_calc_types objects gets constructed from the same std::u32string and then passed directly to unicode::bidi_calc: std::u32string text; unicode::bidi_calc_types types{text}; types.setbnl(text); // Optional // types.types is a std::vector of enum_bidi_types_t values auto [levels, direction]=unicode::bidi_calc(types); This provides the means to access the intermediate enum_bidi_types_t values that get calculated from the Unicode text string. Note In all cases the std::u32string cannot be a temporary object, and it must remain in scope until unicode::bidi_calc() returns. The optional setbnl() method uses unicode_bidi_setbnl(3) to replace paragraph separators with newline characters, in the unicode string. It requires the same unicode string that was passed to the constructor as a parameter (because the constructor takes a constant reference, but this method modifies the string. * Several C functions provide a "dry-run" mode by passing a NULL pointer. The C++ API provides separate overloads, with and without the nullable parameter. * Several C functions accept a nullable function pointer, with the NULL function pointer specifying no callback. The C++ functions have a std::function parameter with a default do-nothing closure. * Several C functions accept two parameters, a Unicode character pointer and the embedding level buffer, and a single parameter that specifies the size of both. The equivalent C++ function takes two discrete para- meters, a std::u32string_view and a std::vector and returns an int; a negative value if their sizes differ, and 0 if their sizes match, and the requested function completes. The unicode::bidi_embed overload that returns a std::u32string returns an empty string in case of a mismatch. * unicode::bidi_reorder reorders the entire string and its embedding_lev- els by default. The optional starting_pos and n parameters limit the reordering to the indicated subset of the original string (specified as the starting position offset index, and the number of characters). * unicode::bidi_reorder, unicode::bidi_cleanup, unicode::bidi_logical_or- der, unicode::bidi_needs_embed and unicode::bidi_get_direction take two optional parameters (defaulted values or overloaded) specifying an op- tional starting position and number of characters that define a subset of the original string that gets reordered, cleaned up, or has its di- rection determined. This unicode::bidi_cleanup does not trim off the passed in string and embedding level buffer, since it affects only a subset of the string. The number of times the removed character callback gets invoked indi- cates how much the substring should be trimmed off. * unicode::bidi_override modifies the passed-in string as follows: * unicode::bidi_cleanup() is applied with the specified, or de- faulted, cleanup_options * Either the LRO or an RLO override marker gets prepended to the Uni- code string, forcing the entire string to be interpreted in a sin- gle rendering direction, when processed by the Unicode bi-direc- tional algorithm. unicode::bidi_override makes it possible to use a Unicode-aware appli- cation or algorithm in a context that only works with text that's al- ways displayed in a fixed direction, allowing graceful handling of in- put containing bi-directional text. unicode::literals namespace using namespace unicode::literals; std::u32string foo(std::u32string bar) { return bar + LRO; } This namespace contains the following constexpr definitions: * char32_t arrays with literal Unicode character strings containing Uni- code directional, isolate, and override markers, like LRO, RLO and oth- ers. * CLEANUP_EXTRA, CLEANUP_BNL, and CLEANUP_CANONICAL options for uni- code::bidi_cleanup(). SEE ALSO courier-unicode(7), unicode_bidi(3). AUTHOR Sam Varshavchik Author NOTES 1. Unicode Bi-Directional algorithm https://www.unicode.org/reports/tr9/tr9-51.html Courier Unicode Library 04/12/2026 UNICODE::BIDI(3)
NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | AUTHOR | NOTES
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