curs_getcchar 3x 2024-04-20 ncurses 6.5 Library calls

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


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


       #include <curses.h>

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

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



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

       o   Extracts information from a cchar_t value wch

       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  wch,
           into the array pointed to by wc.

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

       o   Obtains the number of wide characters pointed to by wch

       o   Does not change the data referenced by attrs or color_pair


       The  setcchar  function  initializes  the location pointed to by wch by

       o   The character attributes in attrs

       o   The color pair in color_pair

       o   The wide-character string pointed to by wc.   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.


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

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

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


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


       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.


       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

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

       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


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

ncurses 6.5                       2024-04-20                 curs_getcchar(3x)