curs_add_wch 3x 2023-11-25 ncurses 6.4 Library calls

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


       add_wch, wadd_wch, mvadd_wch, mvwadd_wch, echo_wchar, wecho_wchar - add
       a curses complex character to a window and 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:

       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

       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.


       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:





       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(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  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.


       These functions are described in the XSI Curses standard, Issue 4.  The
       defaults specified for  line-drawing  characters  apply  in  the  POSIX

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 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, 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 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).

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.


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

ncurses 6.4                       2023-11-25                  curs_add_wch(3x)