# curs_getcchar 3x 2023-12-16 ncurses 6.4 Library calls

    curs_getcchar(3x)                Library calls               curs_getcchar(3x)

## NAME

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

## SYNOPSIS

           #include <curses.h>

           int getcchar(
                   const cchar_t *wcval,
                   wchar_t *wch,
                   attr_t *attrs,
                   short *color_pair,
                   void *opts );

           int setcchar(
                   cchar_t *wcval,
                   const wchar_t *wch,
                   const attr_t attrs,
                   short color_pair,
                   const void *opts );

## DESCRIPTION

### getcchar

           The getcchar function gets a wide-character string and rendition from a
           cchar_t  argument.   When  wch  is  not  a  null  pointer, the getcchar
           function does the following:

           o   Extracts information from a cchar_t value wcval

           o   Stores the character attributes in the location pointed to by attrs

           o   Stores the color pair in the location pointed to by color_pair

           o   Stores the wide-character string, characters referenced  by  wcval,
               into the array pointed to by wch.

           When wch is a null pointer, the getcchar function does the following:

           o   Obtains the number of wide characters pointed to by wcval

           o   Does not change the data referenced by attrs or color_pair

### setcchar

           The  setcchar  function initializes the location pointed to by wcval by
           using:

           o   The character attributes in attrs

           o   The color pair in color_pair

           o   The wide-character string pointed to by wch.  The  string  must  be
               L'\0' terminated, contain at most one spacing character, which must
               be the first.

               Up to CCHARW_MAX-1 non-spacing characters may  follow.   Additional
               non-spacing characters are ignored.

               The string may contain a single control character instead.  In that
               case, no non-spacing characters are allowed.

## RETURN VALUE

           When wch is a  null  pointer,  getcchar  returns  the  number  of  wide
           characters referenced by wcval, including one for a trailing null.

           When  wch  is  not  a null pointer, getcchar returns OK upon successful
           completion, and ERR otherwise.

           Upon successful completion, setcchar returns OK.  Otherwise, it returns
           ERR.

## NOTES

           The wcval argument may be a value generated by a call to setcchar or by
           a function that has a cchar_t output argument.  If wcval is constructed
           by any other means, the effect is unspecified.

## EXTENSIONS

           X/Open  Curses  documents the opts argument as reserved for future use,
           saying that it must be null.  This implementation uses  that  parameter
           in ABI 6 for the functions which have a color pair parameter to support
           extended color pairs:

           o   For  functions  which modify the color, e.g., setcchar, if opts  is
               set it is treated as a pointer to int, and used to  set  the  color
               pair instead of the short pair parameter.

           o   For functions which retrieve the color, e.g., getcchar, if opts  is
               set it is treated as a pointer to int, and  used  to  retrieve  the
               color pair as an int value,  in  addition  retrieving  it  via  the
               standard pointer to short parameter.

## PORTABILITY

           The  CCHARW_MAX  symbol is specific to ncurses.  X/Open Curses does not
           provide details for the layout of the cchar_t structure.  It tells what
           data are stored in it:

           o   a spacing character (wchar_t, i.e., 32-bits).

           o   non-spacing characters (again, wchar_t's).

           o   attributes  (at  least  16 bits, inferred from the various ACS- and
               WACS-flags).

           o   color pair (at least 16 bits,  inferred  from  the  unsigned  short
               type).

           The 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.

           The Unix implementations at the time follow that limit:

           o   AIX 4 and OSF1 4 use the same declaration with an array of  5  non-
               spacing characters z and a single spacing character c.

           o   HP-UX 10  uses  an  opaque  structure with 28 bytes, which is large
               enough for the 6 wchar_t values.

           o   Solaris xpg4 curses uses a single array of 6 wchar_t values.

           This implementation's cchar_t was defined in 1995 using 5 for 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  beginning  to  implement  the
           functions using the structure.

           In  practice, even four non-spacing characters may seem enough.  X/Open
           Curses documents possible uses for  non-spacing  characters,  including
           using  them  for ligatures between characters (a feature apparently not
           supported by any curses implementation).  Unicode does  not  limit  the
           (analogous) number of combining characters, so some applications may be
           affected.

## SEE ALSO

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

    ncurses 6.4                       2023-12-16                 curs_getcchar(3x)