* sale, use or other dealings in this Software without prior written *
* authorization. *
****************************************************************************
- * @Id: curs_attr.3x,v 1.53 2017/03/28 23:31:39 tom Exp @
+ * @Id: curs_attr.3x,v 1.60 2017/10/14 20:01:13 tom Exp @
+ * ---------------------------------------------------------------------------
* attr_get
* .br
* .br
* ---------------------------------------------------------------------------
* ---------------------------------------------------------------------------
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+ * ---------------------------------------------------------------------------
+ * ---------------------------------------------------------------------------
+ * ---------------------------------------------------------------------------
+ * ---------------------------------------------------------------------------
+ * ---------------------------------------------------------------------------
+ * ---------------------------------------------------------------------------
+ * ---------------------------------------------------------------------------
+ * ---------------------------------------------------------------------------
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN">
<HTML>
support more than 256 color pairs.
+</PRE><H2><a name="h2-HISTORY">HISTORY</a></H2><PRE>
+ X/Open Curses is largely based on SVr4 curses, adding support for
+ "wide-characters" (not specific to Unicode). Some of the X/Open dif-
+ ferences from SVr4 curses address the way video attributes can be ap-
+ plied to wide-characters. But aside from that, <STRONG>attrset</STRONG> and <STRONG>attr_set</STRONG>
+ are similar. SVr4 curses provided the basic features for manipulating
+ video attributes. However, earlier versions of curses provided a part
+ of these features.
+
+ As seen in 2.8BSD, curses assumed 7-bit characters, using the eighth
+ bit of a byte to represent the <EM>standout</EM> feature (often implemented as
+ bold and/or reverse video). The BSD curses library provided functions
+ <STRONG>standout</STRONG> and <STRONG>standend</STRONG> which were carried along into X/Open Curses due
+ to their pervasive use in legacy applications.
+
+ Some terminals in the 1980s could support a variety of video at-
+ tributes, although the BSD curses library could do nothing with those.
+ System V (1983) provided an improved curses library. It defined the <STRONG>A_</STRONG>
+ symbols for use by applications to manipulate the other attributes.
+ There are few useful references for the chronology.
+
+ Goodheart's book <EM>UNIX</EM> <EM>Curses</EM> <EM>Explained</EM> (1991) describes SVr3 (1987),
+ commenting on several functions:
+
+ <STRONG>o</STRONG> the <STRONG>attron</STRONG>, <STRONG>attroff</STRONG>, <STRONG>attrset</STRONG> functions (and most of the functions
+ found in SVr4 but not in BSD curses) were introduced by System V,
+
+ <STRONG>o</STRONG> the alternate character set feature with <STRONG>A_ALTCHARSET</STRONG> was added in
+ SVr2 and improved in SVr3 (by adding <STRONG>acs_map[]</STRONG>),
+
+ <STRONG>o</STRONG> <STRONG>start_color</STRONG> and related color-functions were introduced by System
+ V.3.2,
+
+ <STRONG>o</STRONG> pads, soft-keys were added in SVr3, and
+
+ Goodheart did not mention the background character or the <STRONG>cchar_t</STRONG> type.
+ Those are respectively SVr4 and X/Open features. He did mention the <STRONG>A_</STRONG>
+ constants, but did not indicate their values. Those were not the same
+ in different systems, even for those marked as System V.
+
+ Different Unix systems used different sizes for the bit-fields in
+ <STRONG>chtype</STRONG> for <EM>characters</EM> and <EM>colors</EM>, and took into account the different
+ integer sizes (32-bit versus 64-bit).
+
+ This table showing the number of bits for <STRONG>A_COLOR</STRONG> and <STRONG>A_CHARTEXT</STRONG> was
+ gleaned from the curses header files for various operating systems and
+ architectures. The inferred architecture and notes reflect the format
+ and size of the defined constants as well as clues such as the alter-
+ nate character set implementation. A 32-bit library can be used on a
+ 64-bit system, but not necessarily the reverse.
+
+ <EM>Year</EM> <EM>System</EM> <EM>Arch</EM> <EM>Color</EM> <EM>Char</EM> <EM>Notes</EM>
+ ----------------------------------------------------------------
+ 1992 Solaris 5.2 32 6 17 SVr4 curses
+ 1992 HPUX 9 32 no 8 SVr2 curses
+ 1992 AIX 3.2 32 no 23 SVr2 curses
+ 1994 OSF/1 r3 32 no 23 SVr2 curses
+ 1995 HP-UX 10.00 32 6 16 SVr3 "curses_colr"
+ 1995 HP-UX 10.00 32 6 8 SVr4, X/Open curses
+ 1995 Solaris 5.4 32/64 7 16 X/Open curses
+ 1996 AIX 4.2 32 7 16 X/Open curses
+ 1996 OSF/1 r4 32 6 16 X/Open curses
+ 1997 HP-UX 11.00 32 6 8 X/Open curses
+ 2000 U/Win 32/64 7/31 16 uses <STRONG>chtype</STRONG>
+
+ Notes:
+
+ Regarding HP-UX,
+
+ <STRONG>o</STRONG> HP-UX 10.20 (1996) added support for 64-bit PA-RISC processors
+ in 1996.
+
+ <STRONG>o</STRONG> HP-UX 10.30 (1997) marked "curses_colr" obsolete. That version
+ of curses was dropped with HP-UX 11.30 in 2006.
+
+ Regarding OSF/1 (and Tru64),
+
+ <STRONG>o</STRONG> These used 64-bit hardware. Like ncurses, the OSF/1 curses in-
+ terface is not customized for 32-bit and 64-bit versions.
+
+ <STRONG>o</STRONG> Unlike other systems which evolved from AT&T code, OSF/1 provid-
+ ed a new implementation for X/Open curses.
+
+ Regarding Solaris,
+
+ <STRONG>o</STRONG> The initial release of Solaris was in 1992.
+
+ <STRONG>o</STRONG> The <EM>xpg4</EM> (X/Open) curses was developed by MKS from 1990 to 1995.
+ Sun's copyright began in 1996.
+
+ <STRONG>o</STRONG> Sun updated the X/Open curses interface after 64-bit support was
+ introduced in 1997, but did not modify the SVr4 curses inter-
+ face.
+
+ Regarding U/Win,
+
+ <STRONG>o</STRONG> Development of the curses library began in 1991, stopped in
+ 2000.
+
+ <STRONG>o</STRONG> Color support was added in 1998.
+
+ <STRONG>o</STRONG> The library uses only <STRONG>chtype</STRONG> (no <STRONG>cchar_t</STRONG>).
+
+ Once X/Open curses was adopted in the mid-1990s, the constraint of a
+ 32-bit interface with many colors and wide-characters for <STRONG>chtype</STRONG> became
+ a moot point. The <STRONG>cchar_t</STRONG> structure (whose size and members are not
+ specified in X/Open Curses) could be extended as needed.
+
+ Other interfaces are rarely used now:
+
+ <STRONG>o</STRONG> BSD curses was improved slightly in 1993/1994 using Keith Bostic's
+ modification to make the library 8-bit clean for <STRONG>nvi</STRONG>. He moved
+ <EM>standout</EM> attribute to a structure member.
+
+ The resulting 4.4BSD curses was replaced by ncurses over the next
+ ten years.
+
+ <STRONG>o</STRONG> U/Win is rarely used now.
+
+
</PRE><H2><a name="h2-EXTENSIONS">EXTENSIONS</a></H2><PRE>
This implementation provides the <STRONG>A_ITALIC</STRONG> attribute for terminals which
have the <STRONG>enter_italics_mode</STRONG> (<STRONG>sitm</STRONG>) and <STRONG>exit_italics_mode</STRONG> (<STRONG>ritm</STRONG>) capa-
<STRONG>WA_BOLD</STRONG> Extra bright or bold
<STRONG>WA_ALTCHARSET</STRONG> Alternate character set
- The XSI curses standard specifies that each pair of corresponding <STRONG>A_</STRONG>
- and <STRONG>WA_</STRONG>-using functions operates on the same current-highlight informa-
- tion.
+ XSI curses does not assign values to these symbols, nor does it state
+ whether or not they are related to the similarly-named A_NORMAL, etc.:
+
+ <STRONG>o</STRONG> The XSI curses standard specifies that each pair of corresponding
+ <STRONG>A_</STRONG> and <STRONG>WA_</STRONG>-using functions operates on the same current-highlight
+ information.
+
+ <STRONG>o</STRONG> However, in some implementations, those symbols have unrelated val-
+ ues.
+
+ For example, the Solaris <EM>xpg4</EM> (X/Open) curses declares <STRONG>attr_t</STRONG> to be
+ an unsigned short integer (16-bits), while <STRONG>chtype</STRONG> is a unsigned in-
+ teger (32-bits). The <STRONG>WA_</STRONG> symbols in this case are different from
+ the <STRONG>A_</STRONG> symbols because they are used for a smaller datatype which
+ does not represent <STRONG>A_CHARTEXT</STRONG> or <STRONG>A_COLOR</STRONG>.
+
+ In this implementation (as in many others), the values happen to be
+ the same because it simplifies copying information between <STRONG>chtype</STRONG>
+ and <STRONG>cchar_t</STRONG> variables.
The XSI standard extended conformance level adds new highlights <STRONG>A_HORI-</STRONG>
<STRONG>ZONTAL</STRONG>, <STRONG>A_LEFT</STRONG>, <STRONG>A_LOW</STRONG>, <STRONG>A_RIGHT</STRONG>, <STRONG>A_TOP</STRONG>, <STRONG>A_VERTICAL</STRONG> (and corresponding
</li>
<li><a href="#h2-VIDEO-ATTRIBUTES">VIDEO ATTRIBUTES</a></li>
<li><a href="#h2-NOTES">NOTES</a></li>
+<li><a href="#h2-HISTORY">HISTORY</a></li>
<li><a href="#h2-EXTENSIONS">EXTENSIONS</a></li>
<li><a href="#h2-PORTABILITY">PORTABILITY</a></li>
<li><a href="#h2-RETURN-VALUE">RETURN VALUE</a></li>
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