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curs_addch(3)                                                    curs_addch(3)




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 nonprintable character, it is drawn in printable form,
       i.e., the ^X notation used by unctrl(3X).  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 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 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   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.

       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).



                                                                  curs_addch(3)

ncurses 6.4 - Generated Wed Jan 4 16:07:49 CST 2023
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