Provided by: ncurses-doc_6.1+20190803-1ubuntu1_all bug


       add_wch,  wadd_wch,  mvadd_wch,  mvwadd_wch,  echo_wchar,  wecho_wchar  -  add  a  complex
       character and rendition to a curses window, then advance the cursor


       #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 );


       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:

       ·   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 to  the  next  spacing  character  on  the

       ·   If wch refers to a non-spacing character, all previous characters at that location are
           preserved.  The non-spacing characters  of  wch  are  added  to  the  spacing  complex
           character, and the rendition specified by wch is ignored.

       ·   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.

       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).

       ACS               Unicode    ASCII     acsc    Glyph
       Name              Default    Default   char    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 double-lines:

       ACS               Unicode   ASCII     acsc    Glyph
       Name              Default   Default   char    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

       and for thick lines:

       ACS               Unicode   ASCII     acsc    Glyph
       Name              Default   Default   char    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


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

       Functions with a “mv” prefix first perform a cursor movement using wmove,  and  return  an
       error if the position is outside the window, or if the window pointer is null.


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


       All  of  these  functions are described in the XSI Curses standard, Issue 4.  The defaults
       specified for line-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

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

       ·   HPUX 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  define  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

       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, HPUX, 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 curs_addch(3X)
       will use only the ASCII default values.

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

       ·   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.

       ·   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

           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

           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: § U+00A7 (section mark), Θ U+0398 (theta), Φ
           U+03A6 (phi), δ U+03B4 (delta), ⌧ U+2327 (x in a rectangle), ╬  U+256C  (forms  double
           vertical and horizontal), and ☒ U+2612 (ballot box with x).


       ncurses(3NCURSES), addch(3NCURSES), attr(3NCURSES), clear(3NCURSES), outopts(3NCURSES),
       refresh(3NCURSES), putwc(3)