# curs_addch 3x 2023-12-23 ncurses 6.4 Library calls

    curs_addch(3x)                   Library calls                  curs_addch(3x)

## NAME

           addch,  waddch,  mvaddch,  mvwaddch, echochar, wechochar - add a curses
           character to a window and advance the cursor

## SYNOPSIS

           #include <curses.h>

           int addch(const chtype ch);
           int waddch(WINDOW *win, const chtype ch);
           int mvaddch(int y, int x, const chtype ch);
           int mvwaddch(WINDOW *win, int y, int x, const chtype ch);

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

## DESCRIPTION

### Adding Characters

           The addch, waddch, mvaddch and mvwaddch routines put the  character  ch
           into  the  given  window  at its current window position, which is then
           advanced.  They are analogous to the standard C  library's  putchar(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(3x)
               is enabled, the scrolling region is scrolled up one line.

           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.

           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
               margin on the next line, scrolling the window if on the last line.

           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 nonprintable character, it is drawn in printable
           form, using the same convention as unctrl(3x):

           o   Control characters are displayed in the ^X notation.

           o   Values above 128 are either meta characters (if the screen has  not
               been  initialized,  or  if  meta(3x)  has been called with a TRUE E
               parameter),  shown  in  the  M-X  notation,  or  are  displayed  as
               themselves.   In  the latter case, the values may not be printable;
               this follows the X/Open specification.

           Calling winch after adding a nonprintable character does not return the
           character  itself,  but instead returns the printable representation of
           the character.

           Video attributes can be combined with a character  argument  passed  to
           addch  or  related  functions by logical-ORing them into the character.
           (Thus, text, including attributes, can be  copied  from  one  place  to
           another  using  inch(3x)  and  addch.)   See the curs_attr(3x) page for
           values 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
           call  to wrefresh.  The knowledge that only a single character is being
           output  is  used  and,  for  non-control  characters,  a   considerable
           performance  gain  may be seen by using these routines instead of their
           equivalents.

### 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
           listed below is used if the acsc capability does not define a terminal-
           specific   replacement   for   it,   or  if  the  terminal  and  locale
           configuration 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

## RETURN VALUE

           All routines return the integer ERR upon failure and OK on success (the
           SVr4 manuals specify only "an  integer  value  other  than  ERR")  upon
           successful  completion, unless otherwise noted in the preceding routine
           descriptions.

           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.

           If it is not  possible  to  add  a  complete  character,  an  error  is
           returned:

           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.

## NOTES

           Note that addch, mvaddch, mvwaddch, and echochar may be macros.

## PORTABILITY

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

### ACS Symbols

           X/Open Curses states that the ACS_ definitions are char constants.  For
           the  wide-character  implementation  (see  curs_add_wch),   there   are
           analogous   WACS_   definitions  which  are  cchar_t  constants.   Some
           implementations 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.

           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.

           o   X/Open Curses (issues 2 through 7) has a  typographical  error  for
               the  ACS_LANTERN  symbol,  equating  its  "VT100+  Character"  to I
               (capital 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,
               apparently  based on the X/Open documentation around 1995).  On the
               other hand, the terminal description gs6300 (AT&T PC6300 with EMOTS
               Terminal Emulator) uses lowercase-i.

           Some  ACS  symbols  (ACS_S3,  ACS_S7,  ACS_LEQUAL,  ACS_GEQUAL, ACS_PI,
           ACS_NEQUAL, ACS_STERLING) were not documented in any publicly  released
           System  V.   However,  many  publicly  available terminfos include acsc
           strings in which their key characters (pryz{|})  are  embedded,  and  a
           second-hand  list  of  their  character descriptions has come to light.
           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,
               and

           o   whether the locale uses UTF-8 encoding.

           In certain cases,  the  terminal  is  unable  to  display  line-drawing
           characters   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-
           character  information  (attributes  and  color) was separated from the
           character 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
           behavior:

           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.

### TABSIZE

           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).

           If ch is a carriage return, the cursor is moved to the beginning of the
           current row of the window.  This is true of other implementations,  but
           is not documented.

## SEE ALSO

           curses(3x),      curs_attr(3x),      curs_clear(3x),     curs_inch(3x),
           curs_outopts(3x), curs_refresh(3x), curs_variables(3x), putc(3)

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

    ncurses 6.4                       2023-12-23                    curs_addch(3x)