1curs_addch(3X) curs_addch(3X)
2
6 addch, waddch, mvaddch, mvwaddch, echochar, wechochar - add a character
7 (with attributes) to a curses window, then advance the cursor
8
10 #include <curses.h>
11 int addch(const chtype ch);
13 int waddch(WINDOW *win, const chtype ch);
14 int mvaddch(int y, int x, const chtype ch);
15 int mvwaddch(WINDOW *win, int y, int x, const chtype ch);
16 int echochar(const chtype ch);
18 int wechochar(WINDOW *win, const chtype ch);
19
21 Adding characters
22 The addch, waddch, mvaddch and mvwaddch routines put the character ch
23 into the given window at its current window position, which is then ad‐
24 vanced. They are analogous to putchar(3) in stdio(3). If the advance
25 is at the right margin:
26 • The cursor automatically wraps to the beginning of the next line.
28 • At the bottom of the current scrolling region, and if scrollok is
30 enabled, the scrolling region is scrolled up one line.
31 • If scrollok is not enabled, writing a character at the lower right
33 margin succeeds. However, an error is returned because it is not
34 possible to wrap to a new line
35 If ch is a tab, newline, carriage return or backspace, the cursor is
37 moved appropriately within the window:
38 • Backspace moves the cursor one character left; at the left edge of
40 a window it does nothing.
41 • Carriage return moves the cursor to the window left margin on the
43 current line.
44 • Newline does a clrtoeol, then moves the cursor to the window left
46 margin on the next line, scrolling the window if on the last line.
47 • Tabs are considered to be at every eighth column. The tab interval
49 may be altered by setting the TABSIZE variable.
50 If ch is any other nonprintable character, it is drawn in printable
52 form, i.e., the ^X notation used by unctrl(3X). Calling winch after
53 adding a nonprintable character does not return the character itself,
54 but instead returns the printable representation of the character.
55 Video attributes can be combined with a character argument passed to
57 addch or related functions by logical-ORing them into the character.
58 (Thus, text, including attributes, can be copied from one place to an‐
59 other using inch(3X) and addch.) See the curs_attr(3X) page for values
60 of predefined video attribute constants that can be usefully OR'ed into
61 characters.
62 Echoing characters
64 The echochar and wechochar routines are equivalent to a call to addch
65 followed by a call to refresh(3X), or a call to waddch followed by a
66 call to wrefresh. The knowledge that only a single character is being
67 output is used and, for non-control characters, a considerable perfor‐
68 mance gain may be seen by using these routines instead of their equiva‐
69 lents.
70 Line Graphics
72 The following variables may be used to add line drawing characters to
73 the screen with routines of the addch family. The default character
74 listed below is used if the acsc capability does not define a terminal-
75 specific replacement for it, or if the terminal and locale configura‐
76 tion requires Unicode but the library is unable to use Unicode.
77 The names are taken from VT100 nomenclature.
79 ACS ACS acsc Glyph
81 Name Default char Name
82 ─────────────────────────────────────────────────────────
83 ACS_BLOCK # 0 solid square block
84 ACS_BOARD # h board of squares
85 ACS_BTEE + v bottom tee
86 ACS_BULLET o ~ bullet
87 ACS_CKBOARD : a checker board (stipple)
88 ACS_DARROW v . arrow pointing down
89 ACS_DEGREE ' f degree symbol
90 ACS_DIAMOND + ` diamond
91 ACS_GEQUAL > > greater-than-or-equal-to
92 ACS_HLINE - q horizontal line
93 ACS_LANTERN # i lantern symbol
94 ACS_LARROW < , arrow pointing left
95 ACS_LEQUAL < y less-than-or-equal-to
96 ACS_LLCORNER + m lower left-hand corner
97 ACS_LRCORNER + j lower right-hand corner
98 ACS_LTEE + t left tee
99 ACS_NEQUAL ! | not-equal
100 ACS_PI * { greek pi
101 ACS_PLMINUS # g plus/minus
102 ACS_PLUS + n plus
103 ACS_RARROW > + arrow pointing right
104 ACS_RTEE + u right tee
105 ACS_S1 - o scan line 1
106 ACS_S3 - p scan line 3
107 ACS_S7 - r scan line 7
108 ACS_S9 _ s scan line 9
109 ACS_STERLING f } pound-sterling symbol
110 ACS_TTEE + w top tee
111 ACS_UARROW ^ - arrow pointing up
112 ACS_ULCORNER + l upper left-hand corner
113 ACS_URCORNER + k upper right-hand corner
114 ACS_VLINE | x vertical line
115
117 All routines return the integer ERR upon failure and OK on success (the
118 SVr4 manuals specify only “an integer value other than ERR”) upon suc‐
119 cessful completion, unless otherwise noted in the preceding routine de‐
120 scriptions.
121 Functions with a “mv” prefix first perform a cursor movement using
123 wmove, and return an error if the position is outside the window, or if
124 the window pointer is null.
125 If it is not possible to add a complete character, an error is re‐
127 turned:
128 • If scrollok is not enabled, writing a character at the lower right
130 margin succeeds. However, an error is returned because it is not
131 possible to wrap to a new line
132 • If an error is detected when converting a multibyte character to a
134 sequence of bytes, or if it is not possible to add all of the re‐
135 sulting bytes in the window, an error is returned.
136
138 Note that addch, mvaddch, mvwaddch, and echochar may be macros.
139
141 All these functions are described in the XSI Curses standard, Issue 4.
142 The defaults specified for forms-drawing characters apply in the POSIX
143 locale.
144 ACS Symbols
146 X/Open Curses states that the ACS_ definitions are char constants. For
147 the wide-character implementation (see curs_add_wch), there are analo‐
148 gous WACS_ definitions which are cchar_t constants. Some implementa‐
149 tions are problematic:
150 • Some implementations define the ACS symbols to a constant (such as
152 Solaris), while others define those to entries in an array.
153 This implementation uses an array acs_map, as done in SVr4 curses.
155 NetBSD also uses an array, actually named _acs_char, with a #define
156 for compatibility.
157 • HPUX curses equates some of the ACS_ symbols to the analogous WACS_
159 symbols as if the ACS_ symbols were wide characters. The misde‐
160 fined symbols are the arrows and other symbols which are not used
161 for line-drawing.
162 • X/Open Curses (issues 2 through 7) has a typographical error for
164 the ACS_LANTERN symbol, equating its “VT100+ Character” to I (capi‐
165 tal I), while the header files for SVr4 curses and the various im‐
166 plementations use i (lowercase).
167 None of the terminal descriptions on Unix platforms use uppercase-
169 I, except for Solaris (i.e., screen's terminal description, appar‐
170 ently based on the X/Open documentation around 1995). On the other
171 hand, the terminal description gs6300 (AT&T PC6300 with EMOTS Ter‐
172 minal Emulator) uses lowercase-i.
173 Some ACS symbols (ACS_S3, ACS_S7, ACS_LEQUAL, ACS_GEQUAL, ACS_PI,
175 ACS_NEQUAL, ACS_STERLING) were not documented in any publicly released
176 System V. However, many publicly available terminfos include acsc
177 strings in which their key characters (pryz{|}) are embedded, and a
178 second-hand list of their character descriptions has come to light.
179 The ACS-prefixed names for them were invented for ncurses(3X).
180 The displayed values for the ACS_ and WACS_ constants depend on
182 • the library configuration, i.e., ncurses versus ncursesw, where the
184 latter is capable of displaying Unicode while the former is not,
185 and
186 • whether the locale uses UTF-8 encoding.
188 In certain cases, the terminal is unable to display line-drawing char‐
190 acters except by using UTF-8 (see the discussion of NCURSES_NO_UTF8_ACS
191 in ncurses(3X)).
192 Character Set
194 X/Open Curses assumes that the parameter passed to waddch contains a
195 single character. As discussed in curs_attr(3X), that character may
196 have been more than eight bits in an SVr3 or SVr4 implementation, but
197 in the X/Open Curses model, the details are not given. The important
198 distinction between SVr4 curses and X/Open Curses is that the non-char‐
199 acter information (attributes and color) was separated from the charac‐
200 ter information which is packed in a chtype to pass to waddch.
201 In this implementation, chtype holds an eight-bit character. But
203 ncurses allows multibyte characters to be passed in a succession of
204 calls to waddch. The other implementations do not do this; a call to
205 waddch passes exactly one character which may be rendered as one or
206 more cells on the screen depending on whether it is printable.
207 Depending on the locale settings, ncurses will inspect the byte passed
209 in each call to waddch, and check if the latest call will continue a
210 multibyte sequence. When a character is complete, ncurses displays the
211 character and moves to the next position in the screen.
212 If the calling application interrupts the succession of bytes in a
214 multibyte character by moving the current location (e.g., using wmove),
215 ncurses discards the partially built character, starting over again.
216 For portability to other implementations, do not rely upon this behav‐
218 ior:
219 • check if a character can be represented as a single byte in the
221 current locale before attempting call waddch, and
222 • call wadd_wch for characters which cannot be handled by waddch.
224 TABSIZE
226 The TABSIZE variable is implemented in SVr4 and other versions of
227 curses, but is not part of X/Open curses (see curs_variables(3X) for
228 more details).
229 If ch is a carriage return, the cursor is moved to the beginning of the
231 current row of the window. This is true of other implementations, but
232 is not documented.
233
235 curses(3X), curs_attr(3X), curs_clear(3X), curs_inch(3X), curs_out‐
236 opts(3X), curs_refresh(3X), curs_variables(3X), putc(3).
237 Comparable functions in the wide-character (ncursesw) library are de‐
239 scribed in curs_add_wch(3X).
240 curs_addch(3X)