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31 .\" $Id: curs_addch.3x,v 1.60 2023/03/11 20:39:26 tom Exp $
47 \fBwechochar\fP \- add a character (with attributes) to a \fBcurses\fP window, then advance the cursor
49 \fB#include <curses.h>\fP
51 \fBint addch(const chtype \fIch\fB);\fR
53 \fBint waddch(WINDOW *\fIwin\fB, const chtype \fIch\fB);\fR
55 \fBint mvaddch(int \fIy\fB, int \fIx\fB, const chtype \fIch\fB);\fR
57 \fBint mvwaddch(WINDOW *\fIwin\fB, int \fIy\fB, int \fIx\fB, const chtype \fIch\fB);\fR
59 \fBint echochar(const chtype \fIch\fB);\fR
61 \fBint wechochar(WINDOW *\fIwin\fB, const chtype \fIch\fB);\fR
65 The \fBaddch\fP, \fBwaddch\fP, \fBmvaddch\fP and \fBmvwaddch\fP routines put
66 the character \fIch\fP into the given window at its current window position,
67 which is then advanced.
68 They are analogous to \fBputchar\fP(3) in \fBstdio\fP(3).
69 If the advance is at the right margin:
71 The cursor automatically wraps to the beginning of the next line.
73 At the bottom of the current scrolling region,
74 and if \fBscrollok\fP(3X) is enabled,
75 the scrolling region is scrolled up one line.
77 If \fBscrollok\fP(3X) is not enabled,
78 writing a character at the lower right margin succeeds.
79 However, an error is returned because
80 it is not possible to wrap to a new line
82 If \fIch\fP is a tab, newline, carriage return or backspace,
83 the cursor is moved appropriately within the window:
85 Backspace moves the cursor one character left; at the left
86 edge of a window it does nothing.
88 Carriage return moves the cursor to the window left margin on the current line.
90 Newline does a \fBclrtoeol\fP,
91 then moves the cursor to the window left margin on the next line,
92 scrolling the window if on the last line.
94 Tabs are considered to be at every eighth column.
95 The tab interval may be altered by setting the \fBTABSIZE\fP variable.
97 If \fIch\fP is any other nonprintable character,
98 it is drawn in printable form,
99 using the same convention as \fBunctrl\fR(3X):
101 Control characters are displayed in the \fB^\fIX\fR notation.
103 Values above 128 are either meta characters (if the screen has not
104 been initialized, or if \fBmeta\fP(3X) has been called with a \fBTRUE\fP E parameter),
105 shown in the \fBM\-\fIX\fR notation, or are displayed as themselves.
106 In the latter case, the values may not be printable;
107 this follows the X/Open specification.
109 Calling \fBwinch\fP after adding a
110 nonprintable character does not return the character itself,
111 but instead returns the printable representation of the character.
113 Video attributes can be combined with a character argument passed to
114 \fBaddch\fP or related functions by logical-ORing them into the character.
115 (Thus, text, including attributes, can be copied from one place to another
116 using \fBinch\fP(3X) and \fBaddch\fP.) See the \fBcurs_attr\fP(3X) page for
117 values of predefined video attribute constants that can be usefully OR'ed
119 .SS Echoing characters
121 The \fBechochar\fP and \fBwechochar\fP routines are equivalent to a call to
122 \fBaddch\fP followed by a call to \fBrefresh\fP(3X), or a call to \fBwaddch\fP
123 followed by a call to \fBwrefresh\fP.
124 The knowledge that only a single
125 character is being output is used and, for non-control characters, a
126 considerable performance gain may be seen by using these routines instead of
129 The following variables may be used to add line drawing characters to the
130 screen with routines of the \fBaddch\fP family.
131 The default character listed
132 below is used if the \fBacsc\fP capability does not define a terminal-specific
134 or if the terminal and locale configuration requires Unicode but the
135 library is unable to use Unicode.
137 The names are taken from VT100 nomenclature.
144 \fBACS\fP \fBACS\fP \fBacsc\fP \fBGlyph\fP
145 \fBName\fP \fBDefault\fP \fBchar\fP \fBName\fP
146 ACS_BLOCK # 0 solid square block
147 ACS_BOARD # h board of squares
148 ACS_BTEE + v bottom tee
149 ACS_BULLET o ~ bullet
150 ACS_CKBOARD : a checker board (stipple)
151 ACS_DARROW v . arrow pointing down
152 ACS_DEGREE ' f degree symbol
153 ACS_DIAMOND + ` diamond
154 ACS_GEQUAL > > greater-than-or-equal-to
155 ACS_HLINE \- q horizontal line
156 ACS_LANTERN # i lantern symbol
157 ACS_LARROW < , arrow pointing left
158 ACS_LEQUAL < y less-than-or-equal-to
159 ACS_LLCORNER + m lower left-hand corner
160 ACS_LRCORNER + j lower right-hand corner
161 ACS_LTEE + t left tee
162 ACS_NEQUAL ! | not-equal
164 ACS_PLMINUS # g plus/minus
166 ACS_RARROW > + arrow pointing right
167 ACS_RTEE + u right tee
168 ACS_S1 \- o scan line 1
169 ACS_S3 \- p scan line 3
170 ACS_S7 \- r scan line 7
171 ACS_S9 \&_ s scan line 9
172 ACS_STERLING f } pound-sterling symbol
174 ACS_UARROW ^ \- arrow pointing up
175 ACS_ULCORNER + l upper left-hand corner
176 ACS_URCORNER + k upper right-hand corner
177 ACS_VLINE | x vertical line
180 All routines return the integer \fBERR\fP upon failure and \fBOK\fP on success
181 (the SVr4 manuals specify only
182 \*(``an integer value other than \fBERR\fP\*('') upon successful completion,
183 unless otherwise noted in the preceding routine descriptions.
185 Functions with a \*(``mv\*('' prefix first perform a cursor movement using
186 \fBwmove\fP, and return an error if the position is outside the window,
187 or if the window pointer is null.
189 If it is not possible to add a complete character,
190 an error is returned:
192 If \fBscrollok\fP(3X) is not enabled,
193 writing a character at the lower right margin succeeds.
194 However, an error is returned because
195 it is not possible to wrap to a new line
197 If an error is detected when converting a multibyte character to a sequence
199 or if it is not possible to add all of the resulting bytes in the window,
200 an error is returned.
202 Note that \fBaddch\fP, \fBmvaddch\fP, \fBmvwaddch\fP, and
203 \fBechochar\fP may be macros.
205 All these functions are described in the XSI Curses standard, Issue 4.
206 The defaults specified for forms-drawing characters apply in the POSIX locale.
209 X/Open Curses states that the \fBACS_\fP definitions are \fBchar\fP constants.
210 For the wide-character implementation (see \fBcurs_add_wch\fP),
211 there are analogous \fBWACS_\fP definitions which are \fBcchar_t\fP constants.
212 Some implementations are problematic:
214 Some implementations define the ACS symbols to a constant
215 (such as Solaris), while others define those to entries in an array.
217 This implementation uses an array \fBacs_map\fP, as done in SVr4 curses.
218 NetBSD also uses an array, actually named \fB_acs_char\fP, with a \fB#define\fP
221 HPUX curses equates some of the \fBACS_\fP symbols
222 to the analogous \fBWACS_\fP symbols as if the \fBACS_\fP symbols were
224 The misdefined symbols are the arrows
225 and other symbols which are not used for line-drawing.
227 X/Open Curses (issues 2 through 7) has a typographical error
228 for the ACS_LANTERN symbol, equating its \*(``VT100+ Character\*(''
229 to \fBI\fP (capital I), while the header files for SVr4 curses
230 and the various implementations use \fBi\fP (lowercase).
232 None of the terminal descriptions on Unix platforms use uppercase-I,
233 except for Solaris (i.e., \fBscreen\fP's terminal description,
234 apparently based on the X/Open documentation around 1995).
235 On the other hand, the terminal description \fIgs6300\fP
236 (AT&T PC6300 with EMOTS Terminal Emulator) uses lowercase-i.
246 were not documented in
247 any publicly released System V.
248 However, many publicly available terminfos
249 include \fBacsc\fP strings in which their key characters (pryz{|}) are
250 embedded, and a second-hand list of their character descriptions has come
252 The ACS-prefixed names for them were invented for \fBncurses\fP(3X).
254 The \fIdisplayed\fP values for the \fBACS_\fP and \fBWACS_\fP constants
257 the library configuration, i.e., \fBncurses\fP versus \fBncursesw\fP,
258 where the latter is capable of displaying Unicode while the former is not, and
260 whether the \fIlocale\fP uses UTF-8 encoding.
262 In certain cases, the terminal is unable to display line-drawing characters
263 except by using UTF-8 (see the discussion of \fBNCURSES_NO_UTF8_ACS\fP in
266 X/Open Curses assumes that the parameter passed to \fBwaddch\fP contains
268 As discussed in \fBcurs_attr\fP(3X), that character may have been
269 more than eight bits in an SVr3 or SVr4 implementation,
270 but in the X/Open Curses model, the details are not given.
271 The important distinction between SVr4 curses and X/Open Curses is
272 that the non-character information (attributes and color) was
273 separated from the character information which is packed in a \fBchtype\fP
274 to pass to \fBwaddch\fP.
276 In this implementation, \fBchtype\fP holds an eight-bit character.
277 But ncurses allows multibyte characters to be passed in a succession
278 of calls to \fBwaddch\fP.
279 The other implementations do not do this;
280 a call to \fBwaddch\fP passes exactly one character
281 which may be rendered as one or more cells on the screen
282 depending on whether it is printable.
284 Depending on the locale settings,
285 ncurses will inspect the byte passed in each call to \fBwaddch\fP,
286 and check if the latest call will continue a multibyte sequence.
287 When a character is \fIcomplete\fP,
288 ncurses displays the character and moves to the next position in the screen.
290 If the calling application interrupts the succession of bytes in
291 a multibyte character by moving the current location (e.g., using \fBwmove\fP),
292 ncurses discards the partially built character,
295 For portability to other implementations,
296 do not rely upon this behavior:
298 check if a character can be represented as a single byte in the current locale
299 before attempting call \fBwaddch\fP, and
301 call \fBwadd_wch\fP for characters which cannot be handled by \fBwaddch\fP.
304 The \fBTABSIZE\fP variable is implemented in SVr4 and other versions of curses,
305 but is not part of X/Open curses
306 (see \fBcurs_variables\fP(3X) for more details).
308 If \fIch\fP is a carriage return,
309 the cursor is moved to the beginning of the current row of the window.
310 This is true of other implementations, but is not documented.
314 \fBcurs_clear\fP(3X),
316 \fBcurs_outopts\fP(3X),
317 \fBcurs_refresh\fP(3X),
318 \fBcurs_variables\fP(3X),
321 Comparable functions in the wide-character (ncursesw) library are
323 \fBcurs_add_wch\fP(3X).
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