+ 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-
+ bilities. Italics are not mentioned in X/Open Curses. Unlike the oth-
+ er video attributes, <STRONG>A_ITALIC</STRONG> is unrelated to the <STRONG>set_attributes</STRONG> capa-
+ bilities. This implementation makes the assumption that <STRONG>exit_at-</STRONG>
+ <STRONG>tribute_mode</STRONG> may also reset italics.
+
+ Each of the functions added by XSI Curses has a parameter <EM>opts</EM>, which
+ X/Open Curses still (after more than twenty years) documents as re-
+ served for future use, saying that it should be <STRONG>NULL</STRONG>. This implementa-
+ tion uses that parameter in ABI 6 for the functions which have a color-
+ pair parameter to support <EM>extended</EM> <EM>color</EM> <EM>pairs</EM>:
+
+ <STRONG>o</STRONG> For functions which modify the color, e.g., <STRONG>wattr_set</STRONG>, if <EM>opts</EM> is
+ set it is treated as a pointer to <STRONG>int</STRONG>, and used to set the color
+ pair instead of the <STRONG>short</STRONG> <EM>pair</EM> parameter.
+
+ <STRONG>o</STRONG> For functions which retrieve the color, e.g., <STRONG>wattr_get</STRONG>, if <EM>opts</EM> is
+ set it is treated as a pointer to <STRONG>int</STRONG>, and used to retrieve the
+ color pair as an <STRONG>int</STRONG> value, in addition retrieving it via the stan-
+ dard pointer to <STRONG>short</STRONG> parameter.
+
+ The remaining functions which have <EM>opts</EM>, but do not manipulate color,
+ e.g., <STRONG>wattr_on</STRONG> and <STRONG>wattr_off</STRONG> are not used by this implementation except
+ to check that they are <STRONG>NULL</STRONG>.
+
+
+</PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
+ These functions are supported in the XSI Curses standard, Issue 4. The
+ standard defined the dedicated type for highlights, <STRONG>attr_t</STRONG>, which was
+ not defined in SVr4 curses. The functions taking <STRONG>attr_t</STRONG> arguments were
+ not supported under SVr4.
+
+ Very old versions of this library did not force an update of the screen
+ when changing the attributes. Use <STRONG>touchwin</STRONG> to force the screen to
+ match the updated attributes.
+
+ The XSI Curses standard states that whether the traditional functions
+ <STRONG>attron</STRONG>/<STRONG>attroff</STRONG>/<STRONG>attrset</STRONG> can manipulate attributes other than <STRONG>A_BLINK</STRONG>,
+ <STRONG>A_BOLD</STRONG>, <STRONG>A_DIM</STRONG>, <STRONG>A_REVERSE</STRONG>, <STRONG>A_STANDOUT</STRONG>, or <STRONG>A_UNDERLINE</STRONG> is "unspecified".
+ Under this implementation as well as SVr4 curses, these functions cor-
+ rectly manipulate all other highlights (specifically, <STRONG>A_ALTCHARSET</STRONG>,
+ <STRONG>A_PROTECT</STRONG>, and <STRONG>A_INVIS</STRONG>).
+
+ XSI Curses added these entry points:
+
+ <STRONG>attr_get</STRONG>, <STRONG>attr_on</STRONG>, <STRONG>attr_off</STRONG>, <STRONG>attr_set</STRONG>, <STRONG>wattr_on</STRONG>, <STRONG>wattr_off</STRONG>, <STRONG>wat-</STRONG>
+ <STRONG>tr_get</STRONG>, <STRONG>wattr_set</STRONG>
+
+ The new functions are intended to work with a new series of highlight
+ macros prefixed with <STRONG>WA_</STRONG>. The older macros have direct counterparts in
+ the newer set of names:
+
+ <EM>Name</EM> <EM>Description</EM>
+ ------------------------------------------------------------
+ <STRONG>WA_NORMAL</STRONG> Normal display (no highlight)
+ <STRONG>WA_STANDOUT</STRONG> Best highlighting mode of the terminal.
+ <STRONG>WA_UNDERLINE</STRONG> Underlining
+ <STRONG>WA_REVERSE</STRONG> Reverse video
+ <STRONG>WA_BLINK</STRONG> Blinking
+ <STRONG>WA_DIM</STRONG> Half bright
+ <STRONG>WA_BOLD</STRONG> Extra bright or bold
+ <STRONG>WA_ALTCHARSET</STRONG> Alternate character set
+
+ 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
+ <STRONG>WA_</STRONG> macros for each). As of August 2013, no known terminal provides
+ these highlights (i.e., via the <STRONG>sgr1</STRONG> capability).
+
+
+</PRE><H2><a name="h2-RETURN-VALUE">RETURN VALUE</a></H2><PRE>
+ All routines return the integer <STRONG>OK</STRONG> on success, or <STRONG>ERR</STRONG> on failure.
projects / ncurses.git / blobdiff