# curs_add_wch 3x 2025-02-01 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).
           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 advancement occurs at the right margin,

           o   the  cursor  automatically wraps to the beginning of the next line,
               then,

           o   if  it  was  at  the  bottom  of  the  scrolling  region,  and   if
               scrollok(3x)  is  enabled  for win, the scrolling region scrolls up
               one line.

           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.

           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
           background character; see curs_bkgrnd(3x).

### 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.  The ACS default listed
           below is used if the acs_chars  (acsc)  terminfo  capability  does  not
           define  a  terminal-specific replacement for it, or if the terminal and
           locale configuration requires 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, wadd_wch and wecho_wchar return ERR 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                       2025-02-01                  curs_add_wch(3x)