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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | PORTABILITY | SEE ALSO | COLOPHON |
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curs_addch(3X) curs_addch(3X)
addch, waddch, mvaddch, mvwaddch, echochar, wechochar - add a charac‐
ter (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);
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:
· The cursor automatically wraps to the beginning of the next line.
· At the bottom of the current scrolling region, and if scrollok is
enabled, the scrolling region is scrolled up one line.
· 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:
· Backspace moves the cursor one character left; at the left edge
of a window it does nothing.
· Carriage return moves the cursor to the window left margin on the
current line.
· 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.
· 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
control 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
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.
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.
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 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
· the library configuration, i.e., ncurses versus ncursesw, where
the latter is capable of displaying Unicode while the former is
not, and
· 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 eight bits. 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:
· check if a character can be represented as a single byte in the
current locale before attempting call waddch, and
· call wadd_wch for characters which cannot be handled by waddch.
TABSIZE
The TABSIZE variable is implemented in some versions of curses, but
is not part of X/Open curses.
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_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).
This page is part of the ncurses (new curses) project. Information
about the project can be found at
⟨https://www.gnu.org/software/ncurses/ncurses.html⟩. If you have a
bug report for this manual page, send it to
bug-ncurses-request@gnu.org. This page was obtained from the
project's upstream Git mirror of the CVS repository
⟨git://ncurses.scripts.mit.edu/ncurses.git⟩ on 2018-02-02. (At that
time, the date of the most recent commit that was found in the repos‐
itory was 2018-01-30.) If you discover any rendering problems in
this HTML version of the page, or you believe there is a better or
more up-to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not part
of the original manual page), send a mail to man-pages@man7.org
curs_addch(3X)
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