+ Unicode's descriptions for these characters differs slightly from
+ ncurses, by introducing the term "light" (along with less important
+ details). Here are its descriptions for the normal, thick, and double
+ horizontal lines:
+
+ <B>o</B> U+2500 BOX DRAWINGS LIGHT HORIZONTAL
+
+ <B>o</B> U+2501 BOX DRAWINGS HEAVY HORIZONTAL
+
+ <B>o</B> U+2550 BOX DRAWINGS DOUBLE HORIZONTAL
+
+
+</PRE><H2><a name="h2-RETURN-VALUE">RETURN VALUE</a></H2><PRE>
+ All routines return the integer <B>ERR</B> upon failure and <B>OK</B> on success.
+
+ X/Open does not define any error conditions. This implementation
+ returns an error
+
+ <B>o</B> if the window pointer is null or
+
+ <B>o</B> if it is not possible to add a complete character in the window.
+
+ The latter may be due to different causes:
+
+ <B>o</B> If <B>scrollok</B> 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
+
+ <B>o</B> 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.
+
+ Functions with a "mv" prefix first perform a cursor movement using
+ <B>wmove</B>, and return an error if the position is outside the window, or if
+ the window pointer is null.
+
+
+</PRE><H2><a name="h2-NOTES">NOTES</a></H2><PRE>
+ Note that <B>add_wch</B>, <B>mvadd_wch</B>, <B>mvwadd_wch</B>, and <B>echo_wchar</B> may be macros.
+
+
+</PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
+ All of these functions are described in the XSI Curses standard, Issue
+ 4. The defaults specified for line-drawing characters apply in the
+ POSIX locale.
+
+ X/Open Curses makes it clear that the WACS_ symbols should be defined
+ as a pointer to <B>cchar_t</B> data, e.g., in the discussion of <B>border_set</B>. A
+ few implementations are problematic:
+
+ <B>o</B> NetBSD curses defines the symbols as a <B>wchar_t</B> within a <B>cchar_t</B>.
+
+ <B>o</B> HPUX curses equates some of the <I>ACS</I><B>_</B> symbols to the analogous <I>WACS</I><B>_</B>
+ symbols as if the <I>ACS</I><B>_</B> symbols were wide characters. The
+ misdefined symbols are the arrows and other symbols which are not
+ used for line-drawing.
+
+ X/Open Curses does not define 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.
+
+ Not all Unicode-capable terminals provide support for VT100-style
+ alternate character sets (i.e., the <B>acsc</B> 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, HPUX, Solaris) use only
+ the <B>acsc</B> character-mapping to provide this feature. As a result, those
+ implementations can only use single-byte line-drawing characters.
+ Ncurses 5.3 (2002) provided a table of Unicode values to solve these
+ problems. NetBSD curses incorporated that table in 2010.
+
+ In this implementation, the Unicode values are used instead of the
+ terminal description's <B>acsc</B> mapping as discussed in <B><A HREF="ncurses.3X.html">ncurses(3X)</A></B> for the
+ environment variable <B>NCURSES_NO_UTF8_ACS</B>. In contrast, for the same
+ cases, the line-drawing characters described in <B><A HREF="curs_addch.3X.html">curs_addch(3X)</A></B> will use
+ only the ASCII default values.
+
+ Having Unicode available does not solve all of the problems with line-
+ drawing for curses:
+
+ <B>o</B> The closest Unicode equivalents to the VT100 graphics <I>S1</I>, <I>S3</I>, <I>S7</I>
+ and <I>S9</I> frequently are not displayed at the regular intervals which
+ the terminal used.
+
+ <B>o</B> The <I>lantern</I> 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.
+
+ Lacking documentation, most readers assume that a <I>storm</I> <I>lantern</I> was
+ intended. But there are several possibilities, all with problems.
+
+ 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.
+
+ Most <I>storm</I> <I>lanterns</I> have a tapering glass chimney (to guard against
+ tipping); some have a wire grid protecting the chimney.
+
+ For the tapering appearance, U+2603 was adequate. In use on a
+ terminal, no one can tell what the image represents. Unicode calls
+ it a snowman.
+
+ Others have suggested these alternatives: <section> U+00A7 (section
+ mark), <Theta> U+0398 (theta), <Phi> U+03A6 (phi), <delta> U+03B4
+ (delta), U+2327 (x in a rectangle), U+256C (forms double vertical
+ and horizontal), and U+2612 (ballot box with x).
+
+
+</PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
+ <B><A HREF="curses.3X.html">curses(3X)</A></B>, <B><A HREF="curs_addch.3X.html">curs_addch(3X)</A></B>, <B><A HREF="curs_attr.3X.html">curs_attr(3X)</A></B>, <B><A HREF="curs_clear.3X.html">curs_clear(3X)</A></B>,
+ <B><A HREF="curs_outopts.3X.html">curs_outopts(3X)</A></B>, <B><A HREF="curs_refresh.3X.html">curs_refresh(3X)</A></B>, <B>putwc(3)</B>