addch, waddch, mvaddch, mvwaddch, echochar,
wechochar - add a character (with attributes) to a curses
window, then advance the cursor
#include <ncurses/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:
- 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 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.
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.
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.
If it is not possible to add a complete character, an error is
returned:
- 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 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
analogous WACS_ definitions which are cchar_t constants. Some
implementations are problematic:
- •
- 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.
- 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.
- 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
- 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)).
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:
- 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.
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.