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31 .\" $Id: curs_addch.3x,v 1.65 2023/08/19 19:45:54 tom Exp $
32 .TH curs_addch 3X 2023-08-19 "ncurses 6.4" "Library calls"
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
104 (if the screen has not been initialized,
105 or if \fBmeta\fP(3X) has been called with a \fBTRUE\fP E parameter),
106 shown in the \fBM\-\fIX\fR notation, or are displayed as themselves.
107 In the latter case, the values may not be printable;
108 this follows the X/Open specification.
110 Calling \fBwinch\fP after adding a
111 nonprintable character does not return the character itself,
112 but instead returns the printable representation of the character.
114 Video attributes can be combined with a character argument passed to
115 \fBaddch\fP or related functions by logical-ORing them into the character.
116 (Thus, text, including attributes, can be copied from one place to another
117 using \fBinch\fP(3X) and \fBaddch\fP.) See the \fBcurs_attr\fP(3X) page for
118 values of predefined video attribute constants that can be usefully OR'ed
120 .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.
208 X/Open Curses states that the \fBACS_\fP definitions are \fBchar\fP constants.
209 For the wide-character implementation (see \fBcurs_add_wch\fP),
210 there are analogous \fBWACS_\fP definitions which are \fBcchar_t\fP constants.
211 Some implementations are problematic:
213 Some implementations define the ACS symbols to a constant
214 (such as Solaris), while others define those to entries in an array.
216 This implementation uses an array \fBacs_map\fP, as done in SVr4 curses.
217 NetBSD also uses an array, actually named \fB_acs_char\fP, with a \fB#define\fP
220 HPUX curses equates some of the \fBACS_\fP symbols
221 to the analogous \fBWACS_\fP symbols as if the \fBACS_\fP symbols were
223 The misdefined symbols are the arrows
224 and other symbols which are not used for line-drawing.
226 X/Open Curses (issues 2 through 7) has a typographical error
227 for the ACS_LANTERN symbol, equating its \*(``VT100+ Character\*(''
228 to \fBI\fP (capital I), while the header files for SVr4 curses
229 and the various implementations use \fBi\fP (lowercase).
231 None of the terminal descriptions on Unix platforms use uppercase-I,
232 except for Solaris (i.e., \fBscreen\fP's terminal description,
233 apparently based on the X/Open documentation around 1995).
234 On the other hand, the terminal description \fIgs6300\fP
235 (AT&T PC6300 with EMOTS Terminal Emulator) uses lowercase-i.
245 were not documented in
246 any publicly released System V.
247 However, many publicly available terminfos
248 include \fBacsc\fP strings in which their key characters (pryz{|}) are
249 embedded, and a second-hand list of their character descriptions has come
251 The ACS-prefixed names for them were invented for \fBncurses\fP(3X).
253 The \fIdisplayed\fP values for the \fBACS_\fP and \fBWACS_\fP constants
256 the library configuration, i.e., \fBncurses\fP versus \fBncursesw\fP,
257 where the latter is capable of displaying Unicode while the former is not, and
259 whether the \fIlocale\fP uses UTF-8 encoding.
261 In certain cases, the terminal is unable to display line-drawing characters
262 except by using UTF-8 (see the discussion of \fBNCURSES_NO_UTF8_ACS\fP in
265 X/Open Curses assumes that the parameter passed to \fBwaddch\fP contains
267 As discussed in \fBcurs_attr\fP(3X), that character may have been
268 more than eight bits in an SVr3 or SVr4 implementation,
269 but in the X/Open Curses model, the details are not given.
270 The important distinction between SVr4 curses and X/Open Curses is
271 that the non-character information (attributes and color) was
272 separated from the character information which is packed in a \fBchtype\fP
273 to pass to \fBwaddch\fP.
275 In this implementation, \fBchtype\fP holds an eight-bit character.
276 But ncurses allows multibyte characters to be passed in a succession
277 of calls to \fBwaddch\fP.
278 The other implementations do not do this;
279 a call to \fBwaddch\fP passes exactly one character
280 which may be rendered as one or more cells on the screen
281 depending on whether it is printable.
283 Depending on the locale settings,
284 ncurses will inspect the byte passed in each call to \fBwaddch\fP,
285 and check if the latest call will continue a multibyte sequence.
286 When a character is \fIcomplete\fP,
287 ncurses displays the character and moves to the next position in the screen.
289 If the calling application interrupts the succession of bytes in
290 a multibyte character by moving the current location (e.g., using \fBwmove\fP),
291 ncurses discards the partially built character,
294 For portability to other implementations,
295 do not rely upon this behavior:
297 check if a character can be represented as a single byte in the current locale
298 before attempting call \fBwaddch\fP, and
300 call \fBwadd_wch\fP for characters which cannot be handled by \fBwaddch\fP.
302 The \fBTABSIZE\fP variable is implemented in SVr4 and other versions of curses,
303 but is not part of X/Open curses
304 (see \fBcurs_variables\fP(3X) for more details).
306 If \fIch\fP is a carriage return,
307 the cursor is moved to the beginning of the current row of the window.
308 This is true of other implementations, but is not documented.
312 \fBcurs_clear\fP(3X),
314 \fBcurs_outopts\fP(3X),
315 \fBcurs_refresh\fP(3X),
316 \fBcurs_variables\fP(3X),
319 Comparable functions in the wide-character (ncursesw) library are
321 \fBcurs_add_wch\fP(3X).
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