# curs_addch 3x

    curs_addch(3x)                                                  curs_addch(3x)

## NAME

           addch, waddch, mvaddch, mvwaddch, echochar, wechochar - add a character
           (with attributes) to a curses window, then 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  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
               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  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
           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 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
           call  to wrefresh.  The knowledge that only a single character is being
           output is used and, for non-control characters, a considerable  perfor-
           mance gain may be seen by using these routines instead of their equiva-
           lents.

### 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 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

## 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 suc-
           cessful 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 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

           All 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 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.

           o   HPUX curses equates some of the ACS_ symbols to the analogous WACS_
               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.

           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 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-
           ior:

           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_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).

                                                                    curs_addch(3x)