curs_addch(3x) curs_addch(3x)
addch, waddch, mvaddch, mvwaddch, echochar, wechochar - add a character
(with attributes) to a curses window, then advance the cursor
#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);
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 val-
ues of predefined video attribute constants that can be usefully OR'ed
into 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.
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
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.
Note that addch, mvaddch, mvwaddch, and echochar may be macros.
All these functions are described in the XSI Curses standard, Issue 4.
The defaults specified for forms-drawing characters apply in the POSIX
locale.
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)).
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.
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.
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)