curs_getcchar(3X)

💖 curs_getcchar — library calls 💖

okay bestie, we're in the ncurses section of the manual (that's the 3X part, iykyk) and this page is ALL about the getcchar and setcchar girlies. let's go 🫶

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✨ NAME ✨

getcchar, setcchar — convert between a wide-character string and a curses complex character

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🌸 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);

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💅 DESCRIPTION 💅

so the curses complex character data type, cchar_t, is a structure type that's literally three things holding hands: a wide-character string, a set of attributes, and a color pair identifier. 🎀

🚨 real talk: the cchar_t structure is opaque. do NOT go poking at its members directly, bestie, that's not the vibe. the library hands you functions to manipulate this type instead. periodt.

🌈 getcchar

getcchar destructures a cchar_t into its components. like un-building a lewk into its individual pieces ✨

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 completely unchanged. no touchy. 🙈

🦋 setcchar

setcchar constructs a curses complex character wch out of the components wc, attrs, and pair. it's giving assembly line, honestly.

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 it's there at all, has to be the first wide character in the string. 👑

up to CCHARW_MAX - 1 non-spacing characters may follow (peep curs_variables(3X) for that). ncurses ignores any additional non-spacing characters. it simply does not see them, bestie.

the string may contain a single control character instead. but in that case? no non-spacing characters allowed. none. zero. that's the rule 💀

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⭐ 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.

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💜 NOTES 💜

wch may be a value stored by setcchar or another curses function with a writable cchar_t argument. but if wch was constructed by any other means, the library's behavior is unspecified. so like… don't. 🫣

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🎀 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. iconic behavior, honestly.

• 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 conversion). 👀

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🌟 PORTABILITY 🌟

apps employing ncurses extensions should condition their use on the visibility of the NCURSES_VERSION preprocessor macro. that's the vibe check for "am i actually on ncurses rn".

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, describing 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. history lesson time, bestie 📚

• 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 misreading 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. 😭 the way that a tiny slip-up echoes through the decades…

in practice, a mere four non-spacing characters may seem adequate. X/Open Curses documents possible applications of non-spacing characters, including their use as ligatures (a feature apparently not supported 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 — but doing so alters the library's ABI. so, like, don't do that casually. 🚨

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🔥 HISTORY 🔥

X/Open Curses Issue 4 (1995) initially specified these functions.

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🌈 SEE ALSO 🌈

curses(3X), curs_attr(3X), curs_color(3X), wcwidth(3)

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and that's the whole page, bestie 💖 this one came from ncurses 6.6, dated 2025-02-23, and it's the curs_getcchar(3X) manual page. go forth and destructure responsibly 🫶✨🎀