# curs_add_wch 3x 2025-04-05 ncurses 6.5 Library calls

    curs_add_wch(3x)                 Library calls                curs_add_wch(3x)

## NAME

           add_wch, wadd_wch, mvadd_wch, mvwadd_wch, echo_wchar, wecho_wchar - add
           a curses complex character to a window, possibly advancing the cursor

## SYNOPSIS

           #include <curses.h>

           int add_wch(const cchar_t * wch);
           int wadd_wch(WINDOW * win, const cchar_t * wch);
           int mvadd_wch(int y, int x, const cchar_t * wch);
           int mvwadd_wch(WINDOW * win, int y, int x,
                 const cchar_t * wch);

           int echo_wchar(const cchar_t * wch);
           int wecho_wchar(WINDOW * win, const cchar_t *wch);

           /* (integer) constants */
           /* ... */ WACS_BLOCK;
           /* ... */ WACS_BOARD;
           /* ... */ WACS_BTEE;
           /* ... */ WACS_BULLET;
           /* ... */ WACS_CKBOARD;
           /* ... */ WACS_DARROW;
           /* ... */ WACS_DEGREE;
           /* ... */ WACS_DIAMOND;
           /* ... */ WACS_HLINE;
           /* ... */ WACS_LANTERN;
           /* ... */ WACS_LARROW;
           /* ... */ WACS_LLCORNER;
           /* ... */ WACS_LRCORNER;
           /* ... */ WACS_LTEE;
           /* ... */ WACS_PLMINUS;
           /* ... */ WACS_PLUS;
           /* ... */ WACS_RARROW;
           /* ... */ WACS_RTEE;
           /* ... */ WACS_S1;
           /* ... */ WACS_S9;
           /* ... */ WACS_TTEE;
           /* ... */ WACS_UARROW;
           /* ... */ WACS_ULCORNER;
           /* ... */ WACS_URCORNER;
           /* ... */ WACS_VLINE;
           /* extensions */
           /* ... */ WACS_GEQUAL;
           /* ... */ WACS_LEQUAL;
           /* ... */ WACS_NEQUAL;
           /* ... */ WACS_PI;
           /* ... */ WACS_S3;
           /* ... */ WACS_S7;
           /* ... */ WACS_STERLING;
           /* extensions for thick lines */
           /* ... */ WACS_T_BTEE;
           /* ... */ WACS_T_HLINE;
           /* ... */ WACS_T_LLCORNER;
           /* ... */ WACS_T_LRCORNER;
           /* ... */ WACS_T_LTEE;
           /* ... */ WACS_T_PLUS;
           /* ... */ WACS_T_RTEE;
           /* ... */ WACS_T_TTEE;
           /* ... */ WACS_T_ULCORNER;
           /* ... */ WACS_T_URCORNER;
           /* ... */ WACS_T_VLINE;
           /* extensions for double lines */
           /* ... */ WACS_D_BTEE;
           /* ... */ WACS_D_HLINE;
           /* ... */ WACS_D_LLCORNER;
           /* ... */ WACS_D_LRCORNER;
           /* ... */ WACS_D_LTEE;
           /* ... */ WACS_D_PLUS;
           /* ... */ WACS_D_RTEE;
           /* ... */ WACS_D_TTEE;
           /* ... */ WACS_D_ULCORNER;
           /* ... */ WACS_D_URCORNER;
           /* ... */ WACS_D_VLINE;

## DESCRIPTION

### wadd_wch

           wadd_wch writes the curses complex character wch  to  the  window  win,
           then  may  advance  the  cursor position, analogously to the standard C
           library's putwchar(3).  ncurses(3x)  describes  the  variants  of  this
           function.

           Construct  a curses complex character from a wchar_t with setcchar(3x).
           A cchar_t can be copied from  place  to  place  using  win_wch(3x)  and
           wadd_wch.   See  curs_attr(3x)  for values of predefined constants that
           can be usefully "or"ed with characters.  A complex character whose only
           character  component  is  a  wide  space,  and  whose only attribute is
           WA_NORMAL, is a  blank  character,  and  therefore  combines  with  the
           window's background character; see curs_bkgrnd(3x).

           Much behavior depends on whether the wide characters in wch are spacing
           or non-spacing; see subsection "Complex Characters" below.

           o   If wch contains a spacing character,  then  any  character  at  the
               cursor  is  first  removed.   The  complex  character wch, with its
               attributes and color pair  identifier,  becomes  the  base  of  the
               active complex character.

           o   If wch contains only non-spacing characters, they are combined with
               the active complex character.  curses ignores  its  attributes  and
               color pair identifier, and does not advance the cursor.

           Further  non-spacing  characters added with wadd_wch are not written at
           the new cursor position but combine with the active  complex  character
           until  another spacing character is written to the window or the cursor
           is moved.

           If the cursor is  not  at  the  bottom  of  the  scrolling  region  and
           advancement  occurs at the right margin, the cursor automatically wraps
           to the beginning of the next line.

           If the cursor is at the bottom of the scrolling region when advancement
           occurs  at  the  right margin, and scrollok(3x) is enabled for win, the
           scrolling region scrolls up one line and the  cursor  wraps  as  above.
           Otherwise,  advancement  and scrolling do not occur, and waddch returns
           ERR.

           If wch is a backspace, carriage return, line feed, or tab,  the  cursor
           moves appropriately within the window.

           o   Backspace  moves  the cursor one character left; at the left margin
               of a window, it does nothing.

           o   Carriage return moves the cursor to the left  margin  on  the  same
               line of the window.

           o   Line  feed  does a clrtoeol(3x), then advances as if from the right
               margin.

           o   Tab advances the cursor to the next tab stop (possibly on the  next
               line);  these  are placed at every eighth column by default.  Alter
               the   tab   interval    with    the    TABSIZE    extension;    see
               curs_variables(3x).

           If  wch  is  any other nonprintable character, it is drawn in printable
           form using the same convention as wunctrl(3x).  Calling win_wch(3x)  on
           the  location of a nonprintable character does not return the character
           itself, but its wunctrl(3x) representation.

### wecho_wchar

           echo_wchar  and  wecho_wchar  are  equivalent  to  calling   (w)add_wch
           followed  by  (w)refresh  on  stdscr  or  the specified window.  curses
           interprets these functions as a  hint  that  only  a  single  (complex)
           character  is  being output; for non-control characters, a considerable
           performance gain may be enjoyed by employing them.

### Forms-Drawing Characters

           curses defines macros  starting  with  WACS_  that  can  be  used  with
           wadd_wch  to  write  line-drawing  and  other  symbols  to  the screen.
           ncurses terms these forms-drawing  characters.   curses  uses  the  ACS
           default  listed  below  if the terminal type lacks the acs_chars (acsc)
           capability; that capability does  not  define  a  replacement  for  the
           character;  or  if  the  terminal type and locale configuration require
           Unicode to access these characters, but the library is  unable  to  use
           Unicode.   The "acsc char" column corresponds to how the characters are
           specified in the acs_chars (acsc) string capability, and the characters
           in  it  may  appear on the screen if the terminal type's database entry
           incorrectly advertises ACS support.  The name "ACS" originates  in  the
           Alternate Character Set feature of the DEC VT100 terminal.

                           Unicode   ACS       acsc
           Symbol          Default   Default   char   Glyph Name
           ------------------------------------------------------------------------
           WACS_BLOCK      U+25ae    #         0      solid square block
           WACS_BOARD      U+2592    #         h      board of squares
           WACS_BTEE       U+2534    +         v      bottom tee
           WACS_BULLET     U+00b7    o         ~      bullet
           WACS_CKBOARD    U+2592    :         a      checker board (stipple)
           WACS_DARROW     U+2193    v         .      arrow pointing down
           WACS_DEGREE     U+00b0    '         f      degree symbol
           WACS_DIAMOND    U+25c6    +         `      diamond
           WACS_GEQUAL     U+2265    >         >      greater-than-or-equal-to
           WACS_HLINE      U+2500    -         q      horizontal line
           WACS_LANTERN    U+2603    #         i      lantern symbol
           WACS_LARROW     U+2190    <         ,      arrow pointing left
           WACS_LEQUAL     U+2264    <         y      less-than-or-equal-to
           WACS_LLCORNER   U+2514    +         m      lower left-hand corner
           WACS_LRCORNER   U+2518    +         j      lower right-hand corner
           WACS_LTEE       U+2524    +         t      left tee
           WACS_NEQUAL     U+2260    !         |      not-equal
           WACS_PI         U+03c0    *         {      greek pi
           WACS_PLMINUS    U+00b1    #         g      plus/minus
           WACS_PLUS       U+253c    +         n      plus
           WACS_RARROW     U+2192    >         +      arrow pointing right
           WACS_RTEE       U+251c    +         u      right tee
           WACS_S1         U+23ba    -         o      scan line 1
           WACS_S3         U+23bb    -         p      scan line 3
           WACS_S7         U+23bc    -         r      scan line 7
           WACS_S9         U+23bd    _         s      scan line 9
           WACS_STERLING   U+00a3    f         }      pound-sterling symbol
           WACS_TTEE       U+252c    +         w      top tee
           WACS_UARROW     U+2191    ^         -      arrow pointing up
           WACS_ULCORNER   U+250c    +         l      upper left-hand corner

           WACS_URCORNER   U+2510    +         k      upper right-hand corner
           WACS_VLINE      U+2502    |         x      vertical line

           The  ncurses  wide  API  also defines symbols for thick lines (acsc "J"
           through "N", "T" through "X", and "Q"):

                             Unicode   ASCII     acsc
           ACS Name          Default   Default   Char   Glyph Name
           ------------------------------------------------------------------------
           WACS_T_BTEE       U+253b    +         V      thick tee pointing up
           WACS_T_HLINE      U+2501    -         Q      thick horizontal line
           WACS_T_LLCORNER   U+2517    +         M      thick lower left corner
           WACS_T_LRCORNER   U+251b    +         J      thick lower right corner
           WACS_T_LTEE       U+252b    +         T      thick tee pointing right
           WACS_T_PLUS       U+254b    +         N      thick large plus
           WACS_T_RTEE       U+2523    +         U      thick tee pointing left
           WACS_T_TTEE       U+2533    +         W      thick tee pointing down
           WACS_T_ULCORNER   U+250f    +         L      thick upper left corner
           WACS_T_URCORNER   U+2513    +         K      thick upper right corner
           WACS_T_VLINE      U+2503    |         X      thick vertical line

           and for double lines (acsc "A" through "I", plus "R" and "Y"):

                             Unicode   ASCII     acsc
           ACS Name          Default   Default   Char   Glyph Name
           ------------------------------------------------------------------------
           WACS_D_BTEE       U+2569    +         H      double tee pointing up
           WACS_D_HLINE      U+2550    -         R      double horizontal line
           WACS_D_LLCORNER   U+255a    +         D      double lower left corner
           WACS_D_LRCORNER   U+255d    +         A      double lower right corner
           WACS_D_LTEE       U+2560    +         F      double tee pointing right
           WACS_D_PLUS       U+256c    +         E      double large plus
           WACS_D_RTEE       U+2563    +         G      double tee pointing left
           WACS_D_TTEE       U+2566    +         I      double tee pointing down
           WACS_D_ULCORNER   U+2554    +         C      double upper left corner
           WACS_D_URCORNER   U+2557    +         B      double upper right corner
           WACS_D_VLINE      U+2551    |         Y      double vertical line

           Unicode's descriptions  for  these  characters  differs  slightly  from
           ncurses,  by  introducing  the  term "light" (along with less important
           details).  Here are its descriptions for the normal, thick, and  double
           horizontal lines:

           o   U+2500 BOX DRAWINGS LIGHT HORIZONTAL

           o   U+2501 BOX DRAWINGS HEAVY HORIZONTAL

           o   U+2550 BOX DRAWINGS DOUBLE HORIZONTAL

## RETURN VALUE

           These functions return OK on success and ERR on failure.

           In ncurses, these functions fail if

           o   the curses screen has not been initialized,

           o   (for  functions  taking  a  WINDOW  pointer argument) win is a null
               pointer,

           o   wrapping to a new line is impossible because scrollok(3x)  has  not
               been  called  on win (or stdscr, as applicable) when writing to its
               bottom right location is attempted, or

           o   it is not possible to  add  a  complete  character  at  the  cursor
               position.

           Functions  prefixed with "mv" first perform cursor movement and fail if
           the position (y, x) is outside the window boundaries.

## NOTES

           add_wch, mvadd_wch, mvwadd_wch, and echo_wchar may  be  implemented  as
           macros.

## EXTENSIONS

           The   symbols  WACS_S3,  WACS_S7,  WACS_LEQUAL,  WACS_GEQUAL,  WACS_PI,
           WACS_NEQUAL,  and  WACS_STERLING  are  not  standard.   However,   many
           publicly   available   terminfo   entries   include   acs_chars  (acsc)
           capabilities in which their key characters (pryz{|}) are embedded,  and
           a  second-hand  list of their character descriptions has come to light.
           The ncurses developers invented WACS-prefixed names for them.

## 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.

           The defaults specified for forms-drawing characters apply in the  POSIX
           locale.   X/Open Curses makes it clear that the WACS_ symbols should be
           defined as a pointer to  cchar_t  data,  e.g.,  in  the  discussion  of
           border_set.  A few implementations are problematic:

           o   NetBSD curses defines the symbols as a wchar_t within a cchar_t.

           o   HP-UX  curses  equates  some  of  the ACS_ symbols to the analogous
               WACS_ symbols as if the ACS_ symbols  were  wide  characters.   The
               misdefined  symbols  are the arrows and other symbols which are not
               used for line-drawing.

           X/Open Curses does not specify  symbols  for  thick-  or  double-lines.
           SVr4 curses implementations defined their line-drawing symbols in terms
           of intermediate symbols.  ncurses extends those symbols, providing  new
           definitions not found in SVr4 implementations.

           Not  all  Unicode-capable  terminals  provide  support  for VT100-style
           alternate character sets (i.e., the acsc_chars (acsc) capability), with
           their  corresponding  line-drawing  characters.   X/Open Curses did not
           address the aspect of integrating Unicode with line-drawing characters.
           Existing  implementations  of System V curses (AIX, HP-UX, Solaris) use
           only the acsc_chars (acsc) character-mapping to provide  this  feature.
           As  a  result,  those  implementations  can  use only single-byte line-
           drawing characters.  ncurses 5.3 (2002) provided  a  table  of  Unicode
           values  to solve these problems.  NetBSD curses incorporated that table
           in 2010.

           ncurses  uses  the  Unicode  values  instead  of  the   terminal   type
           description's acsc_chars (acsc) mapping as discussed in ncurses(3x) for
           the environment variable NCURSES_NO_UTF8_ACS.   In  contrast,  for  the
           same cases, the line-drawing characters described in addch(3x) will use
           only the ASCII default values.

           Having Unicode available does not solve all of the problems with  line-
           drawing for curses:

           o   The  closest  Unicode equivalents to the VT100 graphics S1, S3, S7,
               and S9 frequently are not displayed at the regular intervals  which
               the terminal used.

           o   The  lantern  is  a special case.  It originated with the AT&T 4410
               terminal in the early 1980s.  There is no accessible  documentation
               depicting the lantern symbol on the AT&T terminal.

               Lacking documentation, most readers assume that a storm lantern was
               intended.  But there are several possibilities, all with problems.

               Unicode 6.0 (2010) does provide two lantern  symbols:  U+1F383  and
               U+1F3EE.   Those  were  not  available  in 2002, and are irrelevant
               since they lie outside the Basic Multilingual Plane and as a result
               are unavailable on many terminals.  They are not storm lanterns, in
               any case.

               Most storm lanterns have a tapering glass chimney (to guard against
               tipping); some have a wire grid protecting the chimney.

               For  the  tapering  appearance,   U+2603 was adequate.  In use on a
               terminal, no one can tell what the image represents.  Unicode calls
               it a snowman.

               Others have suggested these alternatives: <section> U+00A7 (section
               mark), <Theta> U+0398 (theta), <Phi> U+03A6 (phi),  <delta>  U+03B4
               (delta),  U+2327 (x in a rectangle),  U+256C (forms double vertical
               and horizontal), and  U+2612 (ballot box with x).

### Complex Characters

           The complex character  type  cchar_t  can  store  more  than  one  wide
           character  (wchar_t).  X/Open Curses does not mention this possibility,
           specifying behavior only  where  wch  is  a  single  character,  either
           spacing or non-spacing.

           ncurses assumes that wch is constructed using setcchar(3x), and in turn
           that the result

           o   contains at most one spacing character at the beginning of its list
               of wide characters, and zero or more non-spacing characters, or

           o   holds one non-spacing character.

           In  the  latter  case,  ncurses  adds  the non-spacing character to the
           active complex character.

## HISTORY

           X/Open Curses Issue 4 (1995) initially specified these functions.   The
           System V  Interface  Definition  (SVID)  Version 4  of  the  same  year
           specified functions named waddwch (and the usual variants),  echowchar,
           and wechowchar.  These were later additions to SVr4.x, not appearing in
           the first SVr4 (1989).  They differed from X/Open's later wadd_wch  and
           wecho_wchar  in that they each took an argument of type wchar_t instead
           of cchar_t.  SVID defined no  WACS_ symbols.

           X/Open Curses  Issue 4  also  defined  many  of  the  WACS_  constants,
           excepting  WACS_GEQUAL,  WACS_LEQUAL,  WACS_NEQUAL,  WACS_PI,  WACS_S3,
           WACS_S7, and WACS_STERLING; and those  for  drawing  thick  and  double
           lines.

           ncurses 5.3 (2002) furnished the remaining WACS_ constants.

## SEE ALSO

           curs_addch(3x) describes comparable functions of the ncurses library in
           its non-wide-character configuration.

           curses(3x),   curs_addwstr(3x),   curs_add_wchstr(3x),   curs_attr(3x),
           curs_bkgrnd(3x),  curs_clear(3x),  curs_getcchar(3x), curs_outopts(3x),
           curs_refresh(3x), curs_variables(3x), putwc(3)

    ncurses 6.5                       2025-04-05                  curs_add_wch(3x)