# curs_add_wch 3x

    curs_add_wch(3x)                                              curs_add_wch(3x)

## NAME

           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

## 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 to the next spacing character on the screen.

           o   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.

           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).

           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
           thick lines (acsc "J" to "V"):

           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

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

           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

           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 does not  define  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 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  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.

## NOTES

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

## PORTABILITY

           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 problematic:

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

           o   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 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, 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:

           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).

## SEE ALSO

           curses(3x), curs_addch(3x), curs_attr(3x), curs_clear(3x),
           curs_outopts(3x), curs_refresh(3x), putwc(3)

                                                                  curs_add_wch(3x)