# curs_add_wch 3x 2024-04-20 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 and advance 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);

## DESCRIPTION

### add_wch

           The add_wch, wadd_wch, mvadd_wch,  and  mvwadd_wch  functions  put  the
           complex  character  wch  into the given window at its current position,
           which is then advanced.  These functions perform wrapping and  special-
           character processing as follows:

           o   If  wch  refers to a spacing character, then any previous character
               at that location is removed.  A new character specified by  wch  is
               placed  at  that  location  with  rendition  specified by wch.  The
               cursor then advances after this spacing character, to  prepare  for
               writing the next character on the screen.

               The newly added spacing character is the base of the active complex
               character.  Subsequent non-spacing characters can be combined  with
               this base until another spacing character is written to the screen,
               or the cursor is moved, e.g., using wmove.

           o   If wch refers to a non-spacing character, it  is  appended  to  the
               active complex character, retaining the previous characters at that
               location.  The rendition specified by wch is ignored.

               The cursor is not advanced after adding  a  non-spacing  character.
               Subsequent calls to add non-spacing characters will update the same
               position.

           o   If the character part of wch is a tab, newline, backspace or  other
               control character, the window is updated and the cursor moves as if
               addch were called.

### echo_wchar

           The echo_wchar function is functionally equivalent to a call to add_wch
           followed  by  a  call  to  refresh(3x).   Similarly, the wecho_wchar is
           functionally equivalent to a call to wadd_wch followed  by  a  call  to
           wrefresh.   The  knowledge that only a single character is being output
           is  taken  into  consideration  and,  for  non-control  characters,   a
           considerable  performance  gain  might  be  seen  by  using  the *echo*
           functions instead of their equivalents.

### Line Graphics

           Like addch(3x), addch_wch accepts symbols which make it simple to  draw
           lines  and  other  frequently  used  special characters.  These symbols
           correspond to the same VT100 line-drawing set as addch(3x).

                           Unicode   ASCII     acsc

           ACS Name        Default   Default   Char   Glyph Name
           ------------------------------------------------------------------------
           WACS_BLOCK      0x25ae    #         0      solid square block
           WACS_BOARD      0x2592    #         h      board of squares
           WACS_BTEE       0x2534    +         v      bottom tee
           WACS_BULLET     0x00b7    o         ~      bullet
           WACS_CKBOARD    0x2592    :         a      checker board (stipple)
           WACS_DARROW     0x2193    v         .      arrow pointing down
           WACS_DEGREE     0x00b0    '         f      degree symbol
           WACS_DIAMOND    0x25c6    +         `      diamond
           WACS_GEQUAL     0x2265    >         >      greater-than-or-equal-to
           WACS_HLINE      0x2500    -         q      horizontal line
           WACS_LANTERN    0x2603    #         i      lantern symbol
           WACS_LARROW     0x2190    <         ,      arrow pointing left
           WACS_LEQUAL     0x2264    <         y      less-than-or-equal-to
           WACS_LLCORNER   0x2514    +         m      lower left-hand corner
           WACS_LRCORNER   0x2518    +         j      lower right-hand corner
           WACS_LTEE       0x2524    +         t      left tee
           WACS_NEQUAL     0x2260    !         |      not-equal
           WACS_PI         0x03c0    *         {      greek pi
           WACS_PLMINUS    0x00b1    #         g      plus/minus
           WACS_PLUS       0x253c    +         n      plus
           WACS_RARROW     0x2192    >         +      arrow pointing right
           WACS_RTEE       0x251c    +         u      right tee
           WACS_S1         0x23ba    -         o      scan line 1
           WACS_S3         0x23bb    -         p      scan line 3
           WACS_S7         0x23bc    -         r      scan line 7
           WACS_S9         0x23bd    _         s      scan line 9
           WACS_STERLING   0x00a3    f         }      pound-sterling symbol
           WACS_TTEE       0x252c    +         w      top tee
           WACS_UARROW     0x2191    ^         -      arrow pointing up
           WACS_ULCORNER   0x250c    +         l      upper left-hand corner
           WACS_URCORNER   0x2510    +         k      upper right-hand corner
           WACS_VLINE      0x2502    |         x      vertical line

           The wide-character configuration of ncurses also  defines  symbols  for
           thick lines (acsc "J" to "V"):

                             Unicode   ASCII     acsc
           ACS Name          Default   Default   Char   Glyph Name
           ------------------------------------------------------------------------
           WACS_T_BTEE       0x253b    +         V      thick tee pointing up
           WACS_T_HLINE      0x2501    -         Q      thick horizontal line
           WACS_T_LLCORNER   0x2517    +         M      thick lower left corner
           WACS_T_LRCORNER   0x251b    +         J      thick lower right corner
           WACS_T_LTEE       0x252b    +         T      thick tee pointing right
           WACS_T_PLUS       0x254b    +         N      thick large plus
           WACS_T_RTEE       0x2523    +         U      thick tee pointing left
           WACS_T_TTEE       0x2533    +         W      thick tee pointing down
           WACS_T_ULCORNER   0x250f    +         L      thick upper left corner
           WACS_T_URCORNER   0x2513    +         K      thick upper right corner
           WACS_T_VLINE      0x2503    |         X      thick vertical line

           and for double-lines (acsc "A" to "I"):

                             Unicode   ASCII     acsc
           ACS Name          Default   Default   Char   Glyph Name
           ------------------------------------------------------------------------
           WACS_D_BTEE       0x2569    +         H      double tee pointing up
           WACS_D_HLINE      0x2550    -         R      double horizontal line
           WACS_D_LLCORNER   0x255a    +         D      double lower left corner
           WACS_D_LRCORNER   0x255d    +         A      double lower right corner
           WACS_D_LTEE       0x2560    +         F      double tee pointing right
           WACS_D_PLUS       0x256c    +         E      double large plus
           WACS_D_RTEE       0x2563    +         G      double tee pointing left

           WACS_D_TTEE       0x2566    +         I      double tee pointing down
           WACS_D_ULCORNER   0x2554    +         C      double upper left corner
           WACS_D_URCORNER   0x2557    +         B      double upper right corner
           WACS_D_VLINE      0x2551    |         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

           All routines return the integer ERR upon failure and OK on success.

           X/Open  Curses  does  not   specify   any   error   conditions.    This
           implementation returns an error

           o   if the window pointer is null or

           o   if it is not possible to add a complete character in the window.

           The latter may be due to different causes:

           o   If  scrollok(3x)  is  not enabled, writing a character at the lower
               right margin succeeds.  However, an error is returned because it is
               not possible to wrap to a new line.

           o   If  an error is detected when converting a multibyte character to a
               sequence of bytes, or if it is not  possible  to  add  all  of  the
               resulting bytes in the window, an error is returned.

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

## NOTES

           Note that add_wch, mvadd_wch, mvwadd_wch, and echo_wchar may be macros.

## PORTABILITY

           These functions are described in X/Open Curses, Issue 4.  The  defaults
           specified for line-drawing characters apply in the POSIX locale.

### WACS Symbols

           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.  This implementation  extends  those  symbols,
           providing new definitions which are not in the SVr4 implementations.

           Not  all  Unicode-capable  terminals  provide  support  for VT100-style
           alternate character  sets  (i.e.,  the  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 Unix curses (AIX, HP-UX, Solaris) use only
           the acsc character-mapping to provide this feature.  As a result, those
           implementations  can  only  use  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.

           In  this  implementation,  the  Unicode  values are used instead of the
           terminal description's 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 BMP and as a result are not generally
               available in 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).   The  X/Open Curses description does not mention
           this possibility, describing only the cases  where  wch  is  a  spacing
           character or a non-spacing character.

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

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

           o   may hold one non-spacing character.

           In  the  latter  case,  ncurses  adds  the non-spacing character to the
           active (base) spacing character.

### TABSIZE

           The TABSIZE variable is implemented  in  SVr4  and  other  versions  of
           curses, but is not specified by X/Open Curses (see curs_variables(3x)).

## 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_clear(3x),  curs_getcchar(3x), curs_outopts(3x), curs_refresh(3x),
           curs_variables(3x), putwc(3)

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