curs_addch 3x

curs_addch(3x)                                                  curs_addch(3x)




       #include <curses.h>

       int addch(const chtype ch);
       int waddch(WINDOW *win, const chtype ch);
       int echochar(const chtype ch);
       int wechochar(WINDOW *win, const chtype ch);


Adding characters

       advanced.  They are  analogous  to  putchar(3)  in  stdio(3).   If  the
       advance is at the right margin:

       o   The cursor automatically wraps to the beginning of the next line.

       o   At  the  bottom of the current scrolling region, and if scrollok is
           enabled, the scrolling region is scrolled up one line.

       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

       If ch is a tab, newline, carriage return or backspace,  the  cursor  is
       moved appropriately within the window:

       o   Backspace  moves the cursor one character left; at the left edge of
           a window it does nothing.

       o   Carriage return moves the cursor to the window left margin  on  the
           current line.

       o   Newline  does  a clrtoeol, then moves the cursor to the window left

       o   Tabs are considered to be at every eighth column.  The tab interval
           may be altered by setting the TABSIZE variable.

       If  ch  is  any  other  control  character, it is drawn in ^X notation.
       Calling winch after adding a control  character  does  not  return  the
       character  itself, but instead returns the ^-representation of the con-
       trol character.

       Video attributes can be combined with a character  argument  passed  to
       another using inch(3x) and addch.)  See the curs_attr(3x) page for val-
       ues of predefined video attribute constants that can be usefully  OR'ed
       into characters.

Echoing characters

       The  echochar  and wechochar routines are equivalent to a call to addch
       followed by a call to refresh(3x), or a call to waddch  followed  by  a
       output is used and, for non-control characters, a considerable  perfor-
       mance gain may be seen by using these routines instead of their equiva-

Line Graphics

       The following variables may be used to add line drawing  characters  to
       the  screen  with  routines of the addch family.  The default character
       specific  replacement  for it, or if the terminal and locale configura-
       tion requires Unicode but the library is unable to use Unicode.

       The names are taken from VT100 nomenclature.

       ACS            ACS       acsc   Glyph
       Name           Default   char   Name
       ACS_BLOCK      #         0      solid square block
       ACS_BOARD      #         h      board of squares
       ACS_BTEE       +         v      bottom tee
       ACS_BULLET     o         ~      bullet
       ACS_CKBOARD    :         a      checker board (stipple)
       ACS_DARROW     v         .      arrow pointing down
       ACS_DEGREE     '         f      degree symbol
       ACS_DIAMOND    +         `      diamond
       ACS_GEQUAL     >         >      greater-than-or-equal-to
       ACS_HLINE      -         q      horizontal line
       ACS_LANTERN    #         i      lantern symbol
       ACS_LARROW     <         ,      arrow pointing left
       ACS_LEQUAL     <         y      less-than-or-equal-to
       ACS_LLCORNER   +         m      lower left-hand corner
       ACS_LRCORNER   +         j      lower right-hand corner
       ACS_LTEE       +         t      left tee
       ACS_NEQUAL     !         |      not-equal
       ACS_PI         *         {      greek pi
       ACS_PLMINUS    #         g      plus/minus
       ACS_PLUS       +         n      plus
       ACS_RARROW     >         +      arrow pointing right
       ACS_RTEE       +         u      right tee
       ACS_S1         -         o      scan line 1
       ACS_S3         -         p      scan line 3
       ACS_S7         -         r      scan line 7
       ACS_S9         _         s      scan line 9
       ACS_STERLING   f         }      pound-sterling symbol
       ACS_TTEE       +         w      top tee
       ACS_UARROW     ^         -      arrow pointing up
       ACS_ULCORNER   +         l      upper left-hand corner
       ACS_URCORNER   +         k      upper right-hand corner
       ACS_VLINE      |         x      vertical line


       cessful completion, unless otherwise noted  in  the  preceding  routine

       the window pointer is null.




       The defaults specified for forms-drawing characters apply in the  POSIX

ACS Symbols

       the wide-character implementation (see curs_add_wch), there are  analo-
       gous  WACS_  definitions which are cchar_t constants.  Some implementa-
       tions are problematic:

       o   Some implementations define the ACS symbols to a constant (such  as
           Solaris), while others define those to entries in an array.

           This  implementation uses an array acs_map, as done in SVr4 curses.
           NetBSD also uses an array, actually named _acs_char, with a #define
           for compatibility.

           symbols as if the ACS_ symbols were wide  characters.   The  misde-
           fined  symbols  are the arrows and other symbols which are not used
           for line-drawing.

       o   X/Open Curses (issues 2 through 7) has a  typographical  error  for
           the ACS_LANTERN symbol, equating its "VT100+ Character" to I (capi-
           tal I), while the header files for  SVr4  curses  and  the  various
           implementations use i (lowercase).

           None  of the terminal descriptions on Unix platforms use uppercase-
           I, except for Solaris (i.e., screen's terminal description,  appar-
           ently based on the X/Open documentation around 1995).  On the other
           hand, the terminal description gs6300 (AT&T PC6300 with EMOTS  Ter-
           minal Emulator) uses lowercase-i.

       ACS_NEQUAL, ACS_STERLING) were not documented in any publicly  released
       System  V.   However,  many  publicly  available terminfos include acsc
       The ACS-prefixed names for them were invented for ncurses(3x).

       The displayed values for the ACS_ and WACS_ constants depend on

       o   the library configuration, i.e., ncurses versus ncursesw, where the
           latter  is  capable  of displaying Unicode while the former is not,

       o   whether the locale uses UTF-8 encoding.

       In certain cases, the terminal is unable to display line-drawing  char-
       acters except by using UTF-8 (see the discussion of NCURSES_NO_UTF8_ACS
       in ncurses(3x)).

Character Set

       X/Open Curses assumes that the parameter passed to  waddch  contains  a
       single  character.   As  discussed in curs_attr(3x), that character may
       have been more than eight bits in an SVr3 or SVr4  implementation,  but
       in  the  X/Open Curses model, the details are not given.  The important
       distinction between SVr4 curses and X/Open Curses is that the non-char-
       acter information (attributes and color) was separated from the charac-
       ter information which is packed in a chtype to pass to waddch.

       In this implementation,  chtype  holds  an  eight-bit  character.   But
       ncurses  allows  multibyte  characters  to be passed in a succession of
       calls to waddch.  The other implementations do not do this; a  call  to
       waddch  passes  exactly  one  character which may be rendered as one or
       more cells on the screen depending on whether it is printable.

       Depending on the locale settings, ncurses will inspect the byte  passed
       in  each  call  to waddch, and check if the latest call will continue a
       multibyte sequence.  When a character is complete, ncurses displays the
       character and moves to the next position in the screen.

       If  the  calling  application  interrupts  the succession of bytes in a
       multibyte character by moving the current location (e.g., using wmove),
       ncurses discards the partially built character, starting over again.

       For  portability to other implementations, do not rely upon this behav-

       o   check if a character can be represented as a  single  byte  in  the
           current locale before attempting call waddch, and

       o   call wadd_wch for characters which cannot be handled by waddch.


       The  TABSIZE  variable  is  implemented  in  SVr4 and other versions of
       curses, but is not part of X/Open curses  (see  curs_variables(3x)  for
       more details).

       is not documented.


       curses(3x),  curs_attr(3x),  curs_clear(3x),  curs_inch(3x),  curs_out-
       opts(3x), curs_refresh(3x), curs_variables(3x), putc(3).

       Comparable functions  in  the  wide-character  (ncursesw)  library  are
       described in curs_add_wch(3x).