'\" t
.\" $OpenBSD: curs_addch.3,v 1.5 2023/10/17 09:52:08 nicm Exp $
.\"
.\"***************************************************************************
.\" Copyright 2018-2022,2023 Thomas E. Dickey                                *
.\" Copyright 1998-2015,2017 Free Software Foundation, Inc.                  *
.\"                                                                          *
.\" Permission is hereby granted, free of charge, to any person obtaining a  *
.\" copy of this software and associated documentation files (the            *
.\" "Software"), to deal in the Software without restriction, including      *
.\" without limitation the rights to use, copy, modify, merge, publish,      *
.\" distribute, distribute with modifications, sublicense, and/or sell       *
.\" copies of the Software, and to permit persons to whom the Software is    *
.\" furnished to do so, subject to the following conditions:                 *
.\"                                                                          *
.\" The above copyright notice and this permission notice shall be included  *
.\" in all copies or substantial portions of the Software.                   *
.\"                                                                          *
.\" THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS  *
.\" OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF               *
.\" MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.   *
.\" IN NO EVENT SHALL THE ABOVE COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,   *
.\" DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR    *
.\" OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR    *
.\" THE USE OR OTHER DEALINGS IN THE SOFTWARE.                               *
.\"                                                                          *
.\" Except as contained in this notice, the name(s) of the above copyright   *
.\" holders shall not be used in advertising or otherwise to promote the     *
.\" sale, use or other dealings in this Software without prior written       *
.\" authorization.                                                           *
.\"***************************************************************************
.\"
.\" $Id: curs_addch.3,v 1.5 2023/10/17 09:52:08 nicm Exp $
.TH curs_addch 3 2023-08-19 "ncurses 6.4" "Library calls"
.ie \n(.g .ds `` \(lq
.el       .ds `` ``
.ie \n(.g .ds '' \(rq
.el       .ds '' ''
.de bP
.ie n  .IP \(bu 4
.el    .IP \(bu 2
..
.SH NAME
\fBaddch\fP,
\fBwaddch\fP,
\fBmvaddch\fP,
\fBmvwaddch\fP,
\fBechochar\fP,
\fBwechochar\fP \- add a character (with attributes) to a \fBcurses\fP window, then advance the cursor
.SH SYNOPSIS
\fB#include <curses.h>\fP
.PP
\fBint addch(const chtype \fIch\fB);\fR
.br
\fBint waddch(WINDOW *\fIwin\fB, const chtype \fIch\fB);\fR
.br
\fBint mvaddch(int \fIy\fB, int \fIx\fB, const chtype \fIch\fB);\fR
.br
\fBint mvwaddch(WINDOW *\fIwin\fB, int \fIy\fB, int \fIx\fB, const chtype \fIch\fB);\fR
.sp
\fBint echochar(const chtype \fIch\fB);\fR
.br
\fBint wechochar(WINDOW *\fIwin\fB, const chtype \fIch\fB);\fR
.br
.SH DESCRIPTION
.SS Adding characters
The \fBaddch\fP, \fBwaddch\fP, \fBmvaddch\fP and \fBmvwaddch\fP routines put
the character \fIch\fP into the given window at its current window position,
which is then advanced.
They are analogous to \fBputchar\fP(3) in \fBstdio\fP(3).
If the advance is at the right margin:
.bP
The cursor automatically wraps to the beginning of the next line.
.bP
At the bottom of the current scrolling region,
and if \fBscrollok\fP(3) is enabled,
the scrolling region is scrolled up one line.
.bP
If \fBscrollok\fP(3) 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
.PP
If \fIch\fP is a tab, newline, carriage return or backspace,
the cursor is moved appropriately within the window:
.bP
Backspace moves the cursor one character left; at the left
edge of a window it does nothing.
.bP
Carriage return moves the cursor to the window left margin on the current line.
.bP
Newline does a \fBclrtoeol\fP,
then moves the cursor to the window left margin on the next line,
scrolling the window if on the last line.
.bP
Tabs are considered to be at every eighth column.
The tab interval may be altered by setting the \fBTABSIZE\fP variable.
.PP
If \fIch\fP is any other nonprintable character,
it is drawn in printable form,
using the same convention as \fBunctrl\fR(3):
.bP
Control characters are displayed in the \fB^\fIX\fR notation.
.bP
Values above 128 are either meta characters
(if the screen has not been initialized,
or if \fBmeta\fP(3) has been called with a \fBTRUE\fP E parameter),
shown in the \fBM\-\fIX\fR notation, or are displayed as themselves.
In the latter case, the values may not be printable;
this follows the X/Open specification.
.PP
Calling \fBwinch\fP after adding a
nonprintable character does not return the character itself,
but instead returns the printable representation of the character.
.PP
Video attributes can be combined with a character argument passed to
\fBaddch\fP or related functions by logical-ORing them into the character.
(Thus, text, including attributes, can be copied from one place to another
using \fBinch\fP(3) and \fBaddch\fP.)  See the \fBcurs_attr\fP(3) page for
values of predefined video attribute constants that can be usefully OR'ed
into characters.
.SS Echoing characters
The \fBechochar\fP and \fBwechochar\fP routines are equivalent to a call to
\fBaddch\fP followed by a call to \fBrefresh\fP(3), or a call to \fBwaddch\fP
followed by a call to \fBwrefresh\fP.
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.
.SS Line Graphics
The following variables may be used to add line drawing characters to the
screen with routines of the \fBaddch\fP family.
The default character listed
below is used if the \fBacsc\fP 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.
.PP
The names are taken from VT100 nomenclature.
.PP
.TS
l l l l
l l l l
_ _ _ _
l l l l.
\fBACS\fP	\fBACS\fP	\fBacsc\fP	\fBGlyph\fP
\fBName\fP	\fBDefault\fP	\fBchar\fP	\fBName\fP
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
.TE
.SH RETURN VALUE
All routines return the integer \fBERR\fP upon failure and \fBOK\fP on success
(the SVr4 manuals specify only
\*(``an integer value other than \fBERR\fP\*('') upon successful completion,
unless otherwise noted in the preceding routine descriptions.
.PP
Functions with a \*(``mv\*('' prefix first perform a cursor movement using
\fBwmove\fP, and return an error if the position is outside the window,
or if the window pointer is null.
.PP
If it is not possible to add a complete character,
an error is returned:
.bP
If \fBscrollok\fP(3) 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
.bP
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.
.SH NOTES
Note that \fBaddch\fP, \fBmvaddch\fP, \fBmvwaddch\fP, and
\fBechochar\fP may be macros.
.SH PORTABILITY
All these functions are described in the XSI Curses standard, Issue 4.
The defaults specified for forms-drawing characters apply in the POSIX locale.
.SS ACS Symbols
X/Open Curses states that the \fBACS_\fP definitions are \fBchar\fP constants.
For the wide-character implementation (see \fBcurs_add_wch\fP),
there are analogous \fBWACS_\fP definitions which are \fBcchar_t\fP constants.
Some implementations are problematic:
.bP
Some implementations define the ACS symbols to a constant
(such as Solaris), while others define those to entries in an array.
.IP
This implementation uses an array \fBacs_map\fP, as done in SVr4 curses.
NetBSD also uses an array, actually named \fB_acs_char\fP, with a \fB#define\fP
for compatibility.
.bP
HPUX curses equates some of the \fBACS_\fP symbols
to the analogous \fBWACS_\fP symbols as if the \fBACS_\fP symbols were
wide characters.
The misdefined symbols are the arrows
and other symbols which are not used for line-drawing.
.bP
X/Open Curses (issues 2 through 7) has a typographical error
for the ACS_LANTERN symbol, equating its \*(``VT100+ Character\*(''
to \fBI\fP (capital I), while the header files for SVr4 curses
and the various implementations use \fBi\fP (lowercase).
.IP
None of the terminal descriptions on Unix platforms use uppercase-I,
except for Solaris (i.e., \fBscreen\fP's terminal description,
apparently based on the X/Open documentation around 1995).
On the other hand, the terminal description \fIgs6300\fP
(AT&T PC6300 with EMOTS Terminal Emulator) uses lowercase-i.
.LP
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 \fBacsc\fP 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 \fBncurses\fP(3).
.LP
The \fIdisplayed\fP values for the \fBACS_\fP and \fBWACS_\fP constants
depend on
.bP
the library configuration, i.e., \fBncurses\fP versus \fBncursesw\fP,
where the latter is capable of displaying Unicode while the former is not, and
.bP
whether the \fIlocale\fP uses UTF-8 encoding.
.LP
In certain cases, the terminal is unable to display line-drawing characters
except by using UTF-8 (see the discussion of \fBNCURSES_NO_UTF8_ACS\fP in
ncurses(3)).
.SS Character Set
X/Open Curses assumes that the parameter passed to \fBwaddch\fP contains
a single character.
As discussed in \fBcurs_attr\fP(3), 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 \fBchtype\fP
to pass to \fBwaddch\fP.
.PP
In this implementation, \fBchtype\fP holds an eight-bit character.
But ncurses allows multibyte characters to be passed in a succession
of calls to \fBwaddch\fP.
The other implementations do not do this;
a call to \fBwaddch\fP passes exactly one character
which may be rendered as one or more cells on the screen
depending on whether it is printable.
.PP
Depending on the locale settings,
ncurses will inspect the byte passed in each call to \fBwaddch\fP,
and check if the latest call will continue a multibyte sequence.
When a character is \fIcomplete\fP,
ncurses displays the character and moves to the next position in the screen.
.PP
If the calling application interrupts the succession of bytes in
a multibyte character by moving the current location (e.g., using \fBwmove\fP),
ncurses discards the partially built character,
starting over again.
.PP
For portability to other implementations,
do not rely upon this behavior:
.bP
check if a character can be represented as a single byte in the current locale
before attempting call \fBwaddch\fP, and
.bP
call \fBwadd_wch\fP for characters which cannot be handled by \fBwaddch\fP.
.SS TABSIZE
The \fBTABSIZE\fP variable is implemented in SVr4 and other versions of curses,
but is not part of X/Open curses
(see \fBcurs_variables\fP(3) for more details).
.LP
If \fIch\fP 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.
.SH SEE ALSO
\fBcurses\fP(3),
\fBcurs_attr\fP(3),
\fBcurs_clear\fP(3),
\fBcurs_inch\fP(3),
\fBcurs_outopts\fP(3),
\fBcurs_refresh\fP(3),
\fBcurs_variables\fP(3),
\fBputc\fP(3).
.PP
Comparable functions in the wide-character (ncursesw) library are
described in
\fBcurs_add_wch\fP(3).