+'\" t
.\"***************************************************************************
-.\" Copyright (c) 2001-2002,2006 Free Software Foundation, Inc. *
+.\" Copyright 2019-2023,2024 Thomas E. Dickey *
+.\" Copyright 2001-2015,2017 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 *
.\" authorization. *
.\"***************************************************************************
.\"
-.\" $Id: curs_add_wch.3x,v 1.6 2006/12/24 15:22:22 tom Exp $
-.TH curs_add_wch 3X ""
+.\" $Id: curs_add_wch.3x,v 1.71 2024/07/27 20:05:18 tom Exp $
+.TH curs_add_wch 3X 2024-07-27 "ncurses @NCURSES_MAJOR@.@NCURSES_MINOR@" "Library calls"
+.ie \n(.g \{\
+.ds `` \(lq
+.ds '' \(rq
+.\}
+.el \{\
+.ie t .ds `` ``
+.el .ds `` ""
+.ie t .ds '' ''
+.el .ds '' ""
+.\}
+.
+.de bP
+.ie n .IP \(bu 4
+.el .IP \(bu 2
+..
.SH NAME
-\fBadd_wch\fP,
-\fBwadd_wch\fP,
-\fBmvadd_wch\fP,
-\fBmvwadd_wch\fP,
-\fBecho_wchar\fP,
-\fBwecho_wchar\fP - add a complex character and rendition to a \fBcurses\fR window, then advance the cursor
+\fB\%add_wch\fP,
+\fB\%wadd_wch\fP,
+\fB\%mvadd_wch\fP,
+\fB\%mvwadd_wch\fP,
+\fB\%echo_wchar\fP,
+\fB\%wecho_wchar\fP \-
+add a \fIcurses\fR complex character to a window, possibly advancing the cursor
.SH SYNOPSIS
+.nf
+\fB#include <curses.h>
.PP
-\fB#include <curses.h>\fP
-.sp
-.B "int add_wch( const cchar_t *\fIwch\fB );"
-.br
-.B "int wadd_wch( WINDOW *\fIwin\fP, const cchar_t *\fIwch\fB );"
-.br
-.B "int mvadd_wch( int \fIy\fP, int \fIx\fP, const cchar_t *\fIwch\fB );"
-.br
-.B "int mvwadd_wch( WINDOW *\fIwin\fP, int \fIy\fP, int \fIx\fP, const cchar_t *\fIwch\fB );"
-.br
-.B "int echo_wchar( const cchar_t *\fIwch\fB );"
-.br
-.B "int wecho_wchar( WINDOW *\fIwin\fP, const cchar_t *\fIwch\fB );"
-.br
+\fBint add_wch(const cchar_t *\fIwch\fP);
+\fBint wadd_wch(WINDOW *\fIwin\fP, const cchar_t *\fIwch\fP);
+\fBint mvadd_wch(int \fIy\fP, int \fIx\fP, const cchar_t *\fIwch\fP);
+\fBint mvwadd_wch(WINDOW *\fIwin\fP, int \fIy\fP, int \fIx\fP, const cchar_t *\fIwch\fP);
+.PP
+\fBint echo_wchar(const cchar_t *\fIwch\fP);
+\fBint wecho_wchar(WINDOW *\fIwin\fP, const cchar_t *\fIwch\fP);
+.fi
.SH DESCRIPTION
+.SS wadd_wch
+.B \%wadd_wch
+writes the complex character
+.I wch
+to the window
+.IR win ","
+then may advance the cursor position,
+analogously to the standard C library's \fI\%putwchar\fP(3).
+\fB\%ncurses\fP(3X) describes the variants of this function.
.PP
-The
-\fBadd_wch\fP,
-\fBwadd_wch\fP,
-\fBmvadd_wch\fP, and
-\fBmvwadd_wch\fP
-functions put the complex character \fIwch\fP into the given
-window at its current position,
-which is then advanced.
-These functions perform
-wrapping and special-character processing as follows:
-.TP 5
--
-If \fIwch\fP refers to a spacing character,
-then any previous character at that location is removed.
-A new character specified by \fIwch\fP is
-placed at that location with rendition specified by \fIwch\fP.
-The cursor then advances to
-the next spacing character on the screen.
-.TP 5
--
-If \fIwch\fP refers to a non-spacing character,
-all previous characters at that location are preserved.
-The non-spacing characters of \fIwch\fP
-are added to the spacing complex character,
-and the rendition specified by \fIwch\fP is ignored.
-.TP 5
--
-If the character part of \fIwch\fP is
-a tab, newline, backspace or other control character,
-the window is updated and the cursor moves as if \fBaddch\fR were called.
-.PP
-The \fBecho_wchar\fP
-function is functionally equivalent to a call to
-\fBadd_wch\fP
-followed by a call to
-\fBrefresh\fP.
-Similarly, the
-\fBwecho_wchar\fP
-is functionally equivalent to a call to
-\fBwadd_wch\fP
-followed by a call to
-\fBwrefresh\fP.
-The knowledge
-that only a single character is being output is taken into consideration and,
-for non-control characters, a considerable performance gain might be seen
-by using the *\fBecho\fP* functions instead of their equivalents.
-.SH RETURN VALUES
-.PP
-All routines return the integer \fBERR\fR upon failure and \fBOK\fR on success.
-.SH NOTES
+Much behavior depends on whether the wide characters in
+.I wch
+are spacing or non-spacing;
+see subsection \*(``Complex Characters\*('' below.
+.bP
+If
+.I wch
+contains a spacing character,
+then any character at the cursor is first removed.
+The complex character
+.IR wch ","
+with its attributes and color pair identifier,
+becomes the
+.I base
+of the
+.IR "active complex character" "."
+.bP
+If
+.I wch
+contains only non-spacing characters,
+.\" XXX: see wadd_wch_literal (the beginning of the array may be nonspacing)
+they are combined with the active complex character.
+.I curses
+ignores its attributes and color pair identifier,
+and does not advance the cursor.
+.PP
+Further non-spacing characters added with
+.B \%wadd_wch
+are not written at the new cursor position but combine with the active
+complex character until another spacing character is written to the
+window or the cursor is moved.
+.PP
+If advancement occurs at the right margin,
+.bP
+the cursor automatically wraps to the beginning of the next line,
+then,
+.bP
+if it was at the bottom of the scrolling region,
+and if \fB\%scrollok\fP(3X) is enabled for
+.IR win ,
+the scrolling region scrolls up one line.
+.PP
+If
+.I wch
+is a
+backspace,
+carriage return,
+line feed,
+or
+tab,
+the cursor moves appropriately within the window.
+.bP
+Backspace moves the cursor one character left;
+at the left margin of a window,
+it does nothing.
+.bP
+Carriage return moves the cursor to the left margin on the same line of
+the window.
+.bP
+Line feed does a \fB\%clrtoeol\fP(3X),
+then advances as if from the right margin.
+.bP
+Tab advances the cursor to the next tab stop
+(possibly on the next line);
+these are placed at every eighth column by default.
+Alter the tab interval with the
+.B \%TABSIZE
+extension;
+see \fB\%curs_variables\fP(3X).
+.PP
+If
+.I wch
+is any other nonprintable character,
+it is drawn in printable form using the same convention as
+\fB\%wunctrl\fP(3X).
+Calling \fB\%win_wch\fP(3X) on the location of a nonprintable character
+does not return the character itself,
+but its \fB\%wunctrl\fP(3X) representation.
+.PP
+A
+.I \%cchar_t
+can be copied from place to place using \fB\%win_wch\fP(3X) and
+.BR \%wadd_wch "."
+.SS wecho_wchar
+.B \%echo_wchar
+and
+.B \%wecho_wchar
+are equivalent to calling
+.RB \%( w ) add_wch
+followed by
+.RB \%( w ) refresh .
+.I curses
+interprets these functions as a hint that only a single (complex)
+character is being output;
+for non-control characters,
+a considerable performance gain may be enjoyed by employing them.
+.\" TODO: Combine the following with the "Line Drawing" subsection of
+.\" terminfo(5) and replace this with a cross reference there.
+.SS "Forms-Drawing Characters"
+.I curses
+defines macros starting with
+.B \%WACS_
+that can be used with
+.B \%wadd_wch
+to write line-drawing and other special characters to the screen.
+.I \%ncurses
+terms these
+.I "forms-drawing characters."
+The ACS default listed below is used if the
+.B \%acs_chars
+.RB \%( acsc )
+.I \%term\%info
+capability does not define a terminal-specific replacement for it,
+or if the terminal and locale configuration requires Unicode to access
+these characters but the library is unable to use Unicode.
+The \*(``acsc char\*('' column corresponds to how the characters are
+specified in the
+.B \%acs_chars
+.RB \%( acsc )
+string capability,
+and the characters in it may appear on the screen if the terminal type's
+database entry incorrectly advertises ACS support.
+The name \*(``ACS\*('' originates in the Alternate Character Set feature
+of the DEC VT100 terminal.
+.PP
+.ie t .ne 4v
+.el .ne 5v
+.TS
+Lb Lb Lb Lb Lb
+Lb Lb Lb Lb Lb
+Lb L L L Lx.
+\& Unicode ACS acsc \&
+Symbol Default Default char Glyph Name
+_
+WACS_BLOCK 0x25ae # 0 T{
+solid square block
+T}
+WACS_BOARD 0x2592 # h board of squares
+WACS_BTEE 0x2534 + v bottom tee
+WACS_BULLET 0x00b7 o ~ bullet
+WACS_CKBOARD 0x2592 : a T{
+checker board (stipple)
+T}
+WACS_DARROW 0x2193 v . T{
+arrow pointing down
+T}
+WACS_DEGREE 0x00b0 ' f degree symbol
+WACS_DIAMOND 0x25c6 + \(ga diamond
+WACS_GEQUAL 0x2265 > > T{
+greater-than-or-equal-to
+T}
+WACS_HLINE 0x2500 \- q horizontal line
+WACS_LANTERN 0x2603 # i lantern symbol
+WACS_LARROW 0x2190 < , T{
+arrow pointing left
+T}
+WACS_LEQUAL 0x2264 < y T{
+less-than-or-equal-to
+T}
+WACS_LLCORNER 0x2514 + m T{
+lower left-hand corner
+T}
+WACS_LRCORNER 0x2518 + j T{
+lower right-hand corner
+T}
+WACS_LTEE 0x2524 + t left tee
+WACS_NEQUAL 0x2260 ! | not-equal
+WACS_PI 0x03c0 * { greek pi
+WACS_PLMINUS 0x00b1 # g plus/minus
+WACS_PLUS 0x253c + n plus
+WACS_RARROW 0x2192 > + T{
+arrow pointing right
+T}
+WACS_RTEE 0x251c + u right tee
+WACS_S1 0x23ba \- o scan line 1
+WACS_S3 0x23bb \- p scan line 3
+WACS_S7 0x23bc \- r scan line 7
+WACS_S9 0x23bd \&_ s scan line 9
+WACS_STERLING 0x00a3 f } T{
+pound-sterling symbol
+T}
+WACS_TTEE 0x252c + w top tee
+WACS_UARROW 0x2191 ^ \- T{
+arrow pointing up
+T}
+WACS_ULCORNER 0x250c + l T{
+upper left-hand corner
+T}
+WACS_URCORNER 0x2510 + k T{
+upper right-hand corner
+T}
+WACS_VLINE 0x2502 | x vertical line
+.TE
+.PP
+The wide-character configuration of \fI\%ncurses\fP also defines symbols
+for thick lines (\fBacsc\fP \*(``J\*('' to \*(``V\*(''):
+.PP
+.TS
+Lb Lb Lb Lb Lb
+Lb Lb Lb Lb Lb
+Lb L L L Lx.
+\& Unicode ASCII acsc \&
+ACS Name Default Default Char Glyph Name
+_
+WACS_T_BTEE 0x253b + V T{
+thick tee pointing up
+T}
+WACS_T_HLINE 0x2501 - Q T{
+thick horizontal line
+T}
+WACS_T_LLCORNER 0x2517 + M T{
+thick lower left corner
+T}
+WACS_T_LRCORNER 0x251b + J T{
+thick lower right corner
+T}
+WACS_T_LTEE 0x252b + T T{
+thick tee pointing right
+T}
+WACS_T_PLUS 0x254b + N T{
+thick large plus
+T}
+WACS_T_RTEE 0x2523 + U T{
+thick tee pointing left
+T}
+WACS_T_TTEE 0x2533 + W T{
+thick tee pointing down
+T}
+WACS_T_ULCORNER 0x250f + L T{
+thick upper left corner
+T}
+WACS_T_URCORNER 0x2513 + K T{
+thick upper right corner
+T}
+WACS_T_VLINE 0x2503 | X T{
+thick vertical line
+T}
+.TE
.PP
-Note that
-\fBadd_wch\fP,
-\fBmvadd_wch\fP,
-\fBmvwadd_wch\fP, and
-\fBecho_wchar\fP
-may be macros.
+and for double-lines (\fBacsc\fP \*(``A\*('' to \*(``I\*(''):
+.PP
+.TS
+Lb Lb Lb Lb Lb
+Lb Lb Lb Lb Lb
+Lb L L L Lx.
+\& Unicode ASCII acsc \&
+ACS Name Default Default Char Glyph Name
+_
+WACS_D_BTEE 0x2569 + H T{
+double tee pointing up
+T}
+WACS_D_HLINE 0x2550 - R T{
+double horizontal line
+T}
+WACS_D_LLCORNER 0x255a + D T{
+double lower left corner
+T}
+WACS_D_LRCORNER 0x255d + A T{
+double lower right corner
+T}
+WACS_D_LTEE 0x2560 + F T{
+double tee pointing right
+T}
+WACS_D_PLUS 0x256c + E T{
+double large plus
+T}
+WACS_D_RTEE 0x2563 + G T{
+double tee pointing left
+T}
+WACS_D_TTEE 0x2566 + I T{
+double tee pointing down
+T}
+WACS_D_ULCORNER 0x2554 + C T{
+double upper left corner
+T}
+WACS_D_URCORNER 0x2557 + B T{
+double upper right corner
+T}
+WACS_D_VLINE 0x2551 | Y T{
+double vertical line
+T}
+.TE
+.PP
+Unicode's descriptions for these characters differs slightly from
+\fI\%ncurses\fP,
+by introducing the term \*(``light\*('' (along with less important details).
+Here are its descriptions for the normal, thick, and double horizontal lines:
+.bP
+U+2500 BOX DRAWINGS LIGHT HORIZONTAL
+.bP
+U+2501 BOX DRAWINGS HEAVY HORIZONTAL
+.bP
+U+2550 BOX DRAWINGS DOUBLE HORIZONTAL
+.SH RETURN VALUE
+These functions return
+.B OK
+on success and
+.B ERR
+on failure.
+In
+.IR \%ncurses ,
+.B \%wadd_wch
+returns
+.B ERR
+if
+.bP
+.I win
+is
+.BR NULL ","
+.bP
+wrapping to a new line is impossible because \fB\%scrollok\fP(3X) has
+not been called on
+.I win
+when writing to its bottom right location is attempted,
+or
+.bP
+it is not possible to add a complete character at the cursor position.
+.PP
+Functions prefixed with \*(``mv\*('' first perform cursor movement and
+fail if the position
+.RI ( y ,
+.IR x )
+is outside the window boundaries.
+.SH NOTES
+.BR add_wch ","
+.BR mvadd_wch ","
+.BR mvwadd_wch ","
+and
+.B echo_wchar
+may be implemented as macros.
+.SH EXTENSIONS
+.SS TABSIZE
+The
+.B TABSIZE
+variable is implemented in SVr4 and other versions of
+.IR curses ,
+but is not specified by X/Open Curses
+(see \fBcurs_variables\fP(3X)).
.SH PORTABILITY
+These functions are described in X/Open Curses, Issue 4.
+It specifies no error conditions for them.
+.PP
+The defaults specified for forms-drawing characters apply in the POSIX
+locale.
+X/Open Curses makes it clear that the WACS_ symbols should be defined as
+a pointer to \fBcchar_t\fP data, e.g., in the discussion of \fBborder_set\fP.
+A few implementations are problematic:
+.bP
+NetBSD curses defines the symbols as a \fBwchar_t\fP within a \fBcchar_t\fP.
+.bP
+HP-UX 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.
+.PP
+X/Open Curses does not specify symbols for thick- or double-lines.
+SVr4 curses implementations defined their line-drawing symbols in
+terms of intermediate symbols.
+This implementation extends those symbols, providing new definitions
+which are not in the SVr4 implementations.
+.PP
+Not all Unicode-capable terminals provide support for VT100-style
+alternate character sets (i.e., the \fBacsc\fP capability),
+with their corresponding line-drawing characters.
+X/Open Curses did not address the aspect of integrating Unicode with
+line-drawing characters.
+Existing implementations of Unix curses (AIX, HP-UX, Solaris)
+use only the \fBacsc\fP character-mapping to provide this feature.
+As a result, those implementations can only use single-byte line-drawing
+characters.
+\fI\%ncurses\fP 5.3 (2002) provided a table of Unicode values to solve
+these problems.
+NetBSD curses incorporated that table in 2010.
+.PP
+In this implementation, the Unicode values are used instead of the
+terminal description's \fBacsc\fP mapping as discussed in
+\fB\%ncurses\fP(3X) for the environment variable
+\fINCURSES_NO_UTF8_ACS\fP.
+In contrast, for the same cases, the line-drawing characters
+described in \fB\%addch\fP(3X) will use only the ASCII default values.
+.PP
+Having Unicode available does not solve all of the problems with
+line-drawing for curses:
+.bP
+The closest Unicode equivalents to the
+VT100 graphics \fIS1\fP, \fIS3\fP, \fIS7\fP and \fIS9\fP
+frequently are not displayed at
+the regular intervals which the terminal used.
+.bP
+The \fIlantern\fP is a special case.
+It originated with the AT&T 4410 terminal in the early 1980s.
+There is no accessible documentation depicting the lantern symbol
+on the AT&T terminal.
+.IP
+Lacking documentation, most readers assume that a \fIstorm lantern\fP
+was intended.
+But there are several possibilities, all with problems.
+.IP
+Unicode 6.0 (2010) does provide two lantern symbols: U+1F383 and U+1F3EE.
+Those were not available in 2002, and are irrelevant since
+they lie outside the BMP and as a result are not generally available
+in terminals.
+They are not storm lanterns, in any case.
+.IP
+Most \fIstorm lanterns\fP have a tapering glass chimney
+(to guard against tipping);
+some have a wire grid protecting the chimney.
+.IP
+For the tapering appearance, \[u2603] U+2603 was adequate.
+In use on a terminal, no one can tell what the image represents.
+Unicode calls it a snowman.
+.IP
+Others have suggested these alternatives:
+\[sc] U+00A7 (section mark),
+\[u0398] U+0398 (theta),
+\[u03A6] U+03A6 (phi),
+\[u03B4] U+03B4 (delta),
+\[u2327] U+2327 (x in a rectangle),
+\[u256C] U+256C (forms double vertical and horizontal), and
+\[u2612] U+2612 (ballot box with x).
+.SS "Complex Characters"
+The complex character type
+.I \%cchar_t
+can store more than one wide character
+.RI \%( wchar_t ).
+X/Open Curses does not mention this possibility,
+specifying behavior only where
+.I wch
+is a single character,
+either spacing or non-spacing.
.PP
-All these functions are described in the XSI Curses standard, Issue 4.
-The defaults specified for forms-drawing characters apply in the POSIX locale.
+.I \%ncurses
+assumes that
+.I wch
+is constructed using \fB\%setcchar\fP(3X),
+and in turn that the result
+.bP
+contains at most one spacing character at the beginning of its list of
+wide characters,
+and zero or more non-spacing characters,
+or
+.bP
+holds one non-spacing character.
.PP
-XSI documents constants beginning with \fBWACS_\fP which are used for
-line-drawing.
-Those are not currently implemented in \fBncurses\fP.
+In the latter case,
+.I \%ncurses
+adds the non-spacing character to the active complex character.
+.SH HISTORY
+These functions were initially specified by X/Open Curses,
+Issue 4.
+The System\ V Interface Definition,
+Version 4 (1995),
+specified functions named
+.I \%waddwch
+and
+.I \%wechowchar
+(and the usual variants).
+.\" SVID 4, vol 3., p. 475
+These were later additions to
+.RI SVr4. x ,
+not appearing in the first SVr4 (1989).
+They differed from X/Open's later
+.I \%wadd_wch
+and
+.I \%wecho_wchar
+in that they each took an argument of type
+.I \%wchar_t
+instead of
+.IR \%cchar_t "."
.SH SEE ALSO
+\fB\%curs_addch\fP(3X) describes comparable functions of the
+.I \%ncurses
+library in its non-wide-character configuration.
.PP
-\fBcurses\fR(3X),
-\fBcurs_addch\fR(3X),
-\fBcurs_attr\fR(3X),
-\fBcurs_clear\fR(3X),
-\fBcurs_outopts\fR(3X),
-\fBcurs_refresh\fR(3X),
-\fBputwc\fR(3)
-.\"#
-.\"# The following sets edit modes for GNU EMACS
-.\"# Local Variables:
-.\"# mode:nroff
-.\"# fill-column:79
-.\"# End:
+\fB\%curses\fP(3X),
+\fB\%curs_addwstr\fP(3X),
+\fB\%curs_add_wchstr\fP(3X),
+\fB\%curs_attr\fP(3X),
+\fB\%curs_clear\fP(3X),
+\fB\%curs_getcchar\fP(3X),
+\fB\%curs_outopts\fP(3X),
+\fB\%curs_refresh\fP(3X),
+\fB\%curs_variables\fP(3X),
+\fB\%putwc\fP(3)