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curs_getcchar(3X) Library calls curs_getcchar(3X) NAME getcchar, setcchar - convert between a wide-character string and a curses complex character SYNOPSIS #include <curses.h> int getcchar(const cchar_t * wch, wchar_t * wc, attr_t * attrs, short * pair, void * opts); int setcchar(cchar_t * wch, const wchar_t * wc, const attr_t attrs, short pair, const void * opts); DESCRIPTION The curses complex character data type cchar_t is a structure type com- prising a wide-character string, a set of attributes, and a color pair identifier. The cchar_t structure is opaque; do not attempt to access its members directly. The library provides functions to manipulate this type. getcchar getcchar destructures a cchar_t into its components. If wc is not a null pointer, getcchar: • stores the wide-character string in the curses complex character wch into wc; • stores the attributes in attrs; and • stores the color pair identifier in pair. If wc is a null pointer, getcchar counts the wchar_t wide characters in wch, returns that value, and leaves attrs and pair unchanged. setcchar setcchar constructs a curses complex character wch from the components wc, attrs, and pair. The wide-character string wch must be terminated with a null wide character L'\0' and must contain at most one spacing character, which, if present, must be the first wide character in the string. Up to CCHARW_MAX - 1 non-spacing characters may follow (see curs_variables(3X)). ncurses ignores any additional non-spacing char- acters. The string may contain a single control character instead. In that case, no non-spacing characters are allowed. RETURN VALUE If getcchar is passed a null pointer as its wc argument, it returns the number of wide characters for a given wch that it would store in wc, counting a trailing null wide character. If getcchar is not passed a null pointer as its wc argument, it returns OK on success and ERR on failure. In ncurses, getcchar returns ERR if either attrs or pair is a null pointer and wc is not. setcchar returns OK on success and ERR on failure. In ncurses, setcchar returns ERR if • wch is a null pointer, • wc starts with a (wide) control character and contains any other wide characters, or • pair has a negative value. NOTES wch may be a value stored by setcchar or another curses function with a writable cchar_t argument. If wch is constructed by any other means, the library's behavior is unspecified. EXTENSIONS X/Open Curses documents the opts argument as reserved for future use, saying that it must be a null pointer. The ncurses 6 ABI uses it with functions that have a color pair parameter to support extended color pairs. • In functions that assign colors, such as setcchar, if opts is not a null pointer, ncurses treats it as a pointer to int, and interprets it instead of the short pair parameter as a color pair identifier. • In functions that retrieve colors, such as getcchar, if opts is not a null pointer, ncurses treats it as a pointer to int, and stores the retrieved color pair identifier there as well as in the short pair parameter (which may therefore undergo a narrowing conver- sion). PORTABILITY Applications employing ncurses extensions should condition their use on the visibility of the NCURSES_VERSION preprocessor macro. These functions are described in X/Open Curses Issue 4. It specifies no error conditions for them. X/Open Curses does not detail the layout of the cchar_t structure, de- scribing only its minimal required contents: • a spacing wide character (wchar_t), • at least five non-spacing wide characters (wchar_t; see below), • attributes (at least 15 bits' worth, inferred from the count of specified WA_ constants), • a color pair identifier (at least 16 bits, inferred from the short type used to encode it). Non-spacing characters are optional, in the sense that zero or more may be stored in a cchar_t. XOpen/Curses specifies a limit: Implementations may limit the number of non-spacing characters that can be associated with a spacing character, provided any limit is at least 5. Then-contemporary Unix implementations adhered to that limit. • AIX 4 and OSF/1 4 used the same declaration with a single spacing wide character c and an array of 5 non-spacing wide characters z. • HP-UX 10 used an opaque structure of 28 bytes, large enough for 6 wchar_t values. • Solaris xcurses uses a single array of 6 wchar_t values. ncurses defined its cchar_t in 1995 using 5 as the total of spacing and non-spacing characters (CCHARW_MAX). That was probably due to a mis- reading of the AIX 4 header files, because the X/Open Curses document was not generally available at that time. Later (in 2002), this detail was overlooked when work began to implement the functions using the structure. In practice, a mere four non-spacing characters may seem adequate. X/Open Curses documents possible applications of non-spacing charac- ters, including their use as ligatures (a feature apparently not sup- ported by any curses implementation). Unicode does not limit the (analogous) number of combining characters in a grapheme cluster; some applications may be affected. ncurses can be compiled with a different CCHARW_MAX value; doing so alters the library's ABI. HISTORY X/Open Curses Issue 4 (1995) initially specified these functions. SEE ALSO curses(3X), curs_attr(3X), curs_color(3X), wcwidth(3) ncurses 6.6 2025-02-23 curs_getcchar(3X)
NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | EXTENSIONS | PORTABILITY | HISTORY | SEE ALSO
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