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(3X)
30 is enabled, the scrolling region is scrolled up one line.
31 • If scrollok(3X) is not enabled, writing a character at the lower
33 right margin succeeds. However, an error is returned because it is
34 not 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, using the same convention as unctrl(3X):
53 • Control characters are displayed in the ^X notation.
55 • Values above 128 are either meta characters (if the screen has not
57 been initialized, or if meta(3X) has been called with a TRUE E pa‐
58 rameter), shown in the M-X notation, or are displayed as them‐
59 selves. In the latter case, the values may not be printable; this
60 follows the X/Open specification.
61 Calling winch after adding a nonprintable character does not return the
63 character itself, but instead returns the printable representation of
64 the character.
65 Video attributes can be combined with a character argument passed to
67 addch or related functions by logical-ORing them into the character.
68 (Thus, text, including attributes, can be copied from one place to an‐
69 other using inch(3X) and addch.) See the curs_attr(3X) page for values
70 of predefined video attribute constants that can be usefully OR'ed into
71 characters.
72 Echoing characters
74 The echochar and wechochar routines are equivalent to a call to addch
75 followed by a call to refresh(3X), or a call to waddch followed by a
76 call to wrefresh. The knowledge that only a single character is being
77 output is used and, for non-control characters, a considerable perfor‐
78 mance gain may be seen by using these routines instead of their equiva‐
79 lents.
80 Line Graphics
82 The following variables may be used to add line drawing characters to
83 the screen with routines of the addch family. The default character
84 listed below is used if the acsc capability does not define a terminal-
85 specific replacement for it, or if the terminal and locale configura‐
86 tion requires Unicode but the library is unable to use Unicode.
87 The names are taken from VT100 nomenclature.
89 ACS ACS acsc Glyph
91 Name Default char Name
92 ─────────────────────────────────────────────────────────
93 ACS_BLOCK # 0 solid square block
94 ACS_BOARD # h board of squares
95 ACS_BTEE + v bottom tee
96 ACS_BULLET o ~ bullet
97 ACS_CKBOARD : a checker board (stipple)
98 ACS_DARROW v . arrow pointing down
99 ACS_DEGREE ' f degree symbol
100 ACS_DIAMOND + ` diamond
101 ACS_GEQUAL > > greater-than-or-equal-to
102 ACS_HLINE - q horizontal line
103 ACS_LANTERN # i lantern symbol
104 ACS_LARROW < , arrow pointing left
105 ACS_LEQUAL < y less-than-or-equal-to
106 ACS_LLCORNER + m lower left-hand corner
107 ACS_LRCORNER + j lower right-hand corner
108 ACS_LTEE + t left tee
109 ACS_NEQUAL ! | not-equal
110 ACS_PI * { greek pi
111 ACS_PLMINUS # g plus/minus
112 ACS_PLUS + n plus
113 ACS_RARROW > + arrow pointing right
114 ACS_RTEE + u right tee
115 ACS_S1 - o scan line 1
116 ACS_S3 - p scan line 3
117 ACS_S7 - r scan line 7
118 ACS_S9 _ s scan line 9
119 ACS_STERLING f } pound-sterling symbol
120 ACS_TTEE + w top tee
121 ACS_UARROW ^ - arrow pointing up
122 ACS_ULCORNER + l upper left-hand corner
123 ACS_URCORNER + k upper right-hand corner
124 ACS_VLINE | x vertical line
125
127 All routines return the integer ERR upon failure and OK on success (the
128 SVr4 manuals specify only “an integer value other than ERR”) upon suc‐
129 cessful completion, unless otherwise noted in the preceding routine de‐
130 scriptions.
131 Functions with a “mv” prefix first perform a cursor movement using
133 wmove, and return an error if the position is outside the window, or if
134 the window pointer is null.
135 If it is not possible to add a complete character, an error is re‐
137 turned:
138 • If scrollok(3X) is not enabled, writing a character at the lower
140 right margin succeeds. However, an error is returned because it is
141 not possible to wrap to a new line
142 • If an error is detected when converting a multibyte character to a
144 sequence of bytes, or if it is not possible to add all of the re‐
145 sulting bytes in the window, an error is returned.
146
148 Note that addch, mvaddch, mvwaddch, and echochar may be macros.
149
151 All these functions are described in the XSI Curses standard, Issue 4.
152 The defaults specified for forms-drawing characters apply in the POSIX
153 locale.
154 ACS Symbols
156 X/Open Curses states that the ACS_ definitions are char constants. For
157 the wide-character implementation (see curs_add_wch), there are analo‐
158 gous WACS_ definitions which are cchar_t constants. Some implementa‐
159 tions are problematic:
160 • Some implementations define the ACS symbols to a constant (such as
162 Solaris), while others define those to entries in an array.
163 This implementation uses an array acs_map, as done in SVr4 curses.
165 NetBSD also uses an array, actually named _acs_char, with a #define
166 for compatibility.
167 • HPUX curses equates some of the ACS_ symbols to the analogous WACS_
169 symbols as if the ACS_ symbols were wide characters. The misde‐
170 fined symbols are the arrows and other symbols which are not used
171 for line-drawing.
172 • X/Open Curses (issues 2 through 7) has a typographical error for
174 the ACS_LANTERN symbol, equating its “VT100+ Character” to I (capi‐
175 tal I), while the header files for SVr4 curses and the various im‐
176 plementations use i (lowercase).
177 None of the terminal descriptions on Unix platforms use uppercase-
179 I, except for Solaris (i.e., screen's terminal description, appar‐
180 ently based on the X/Open documentation around 1995). On the other
181 hand, the terminal description gs6300 (AT&T PC6300 with EMOTS Ter‐
182 minal Emulator) uses lowercase-i.
183 Some ACS symbols (ACS_S3, ACS_S7, ACS_LEQUAL, ACS_GEQUAL, ACS_PI,
185 ACS_NEQUAL, ACS_STERLING) were not documented in any publicly released
186 System V. However, many publicly available terminfos include acsc
187 strings in which their key characters (pryz{|}) are embedded, and a
188 second-hand list of their character descriptions has come to light.
189 The ACS-prefixed names for them were invented for ncurses(3X).
190 The displayed values for the ACS_ and WACS_ constants depend on
192 • the library configuration, i.e., ncurses versus ncursesw, where the
194 latter is capable of displaying Unicode while the former is not,
195 and
196 • whether the locale uses UTF-8 encoding.
198 In certain cases, the terminal is unable to display line-drawing char‐
200 acters except by using UTF-8 (see the discussion of NCURSES_NO_UTF8_ACS
201 in ncurses(3X)).
202 Character Set
204 X/Open Curses assumes that the parameter passed to waddch contains a
205 single character. As discussed in curs_attr(3X), that character may
206 have been more than eight bits in an SVr3 or SVr4 implementation, but
207 in the X/Open Curses model, the details are not given. The important
208 distinction between SVr4 curses and X/Open Curses is that the non-char‐
209 acter information (attributes and color) was separated from the charac‐
210 ter information which is packed in a chtype to pass to waddch.
211 In this implementation, chtype holds an eight-bit character. But
213 ncurses allows multibyte characters to be passed in a succession of
214 calls to waddch. The other implementations do not do this; a call to
215 waddch passes exactly one character which may be rendered as one or
216 more cells on the screen depending on whether it is printable.
217 Depending on the locale settings, ncurses will inspect the byte passed
219 in each call to waddch, and check if the latest call will continue a
220 multibyte sequence. When a character is complete, ncurses displays the
221 character and moves to the next position in the screen.
222 If the calling application interrupts the succession of bytes in a
224 multibyte character by moving the current location (e.g., using wmove),
225 ncurses discards the partially built character, starting over again.
226 For portability to other implementations, do not rely upon this behav‐
228 ior:
229 • check if a character can be represented as a single byte in the
231 current locale before attempting call waddch, and
232 • call wadd_wch for characters which cannot be handled by waddch.
234 TABSIZE
236 The TABSIZE variable is implemented in SVr4 and other versions of
237 curses, but is not part of X/Open curses (see curs_variables(3X) for
238 more details).
239 If ch is a carriage return, the cursor is moved to the beginning of the
241 current row of the window. This is true of other implementations, but
242 is not documented.
243
245 curses(3X), curs_attr(3X), curs_clear(3X), curs_inch(3X), curs_out‐
246 opts(3X), curs_refresh(3X), curs_variables(3X), putc(3).
247 Comparable functions in the wide-character (ncursesw) library are de‐
249 scribed in curs_add_wch(3X).
250 curs_addch(3X)