- These routines manipulate the current attributes of the
- named window, which then apply to all characters that are
- written into the window with waddch, waddstr and wprintw.
- Attributes are a property of the character, and move with
- the character through any scrolling and insert/delete
- line/character operations. To the extent possible, they
- are displayed as appropriate modifications to the graphic
- rendition of characters put on the screen.
+ These routines manipulate the current attributes of the named window,
+ which then apply to all characters that are written into the window
+ with waddch, waddstr and wprintw. Attributes are a property of the
+ character, and move with the character through any scrolling and in-
+ sert/delete line/character operations. To the extent possible, they
+ are displayed as appropriate modifications to the graphic rendition of
+ characters put on the screen.
- These routines do not affect the attributes used when
- erasing portions of the window. See curs_bkgd(3x) for
- functions which modify the attributes used for erasing and
- clearing.
+ These routines do not affect the attributes used when erasing portions
+ of the window. See curs_bkgd(3x) for functions which modify the at-
+ tributes used for erasing and clearing.
- Routines which do not have a WINDOW* parameter apply to
- stdscr.
+ Routines which do not have a WINDOW* parameter apply to stdscr. For
+ example, attr_set is the stdscr variant of wattr_set.
- The attr_set and wattr_set functions set the current at-
- tributes of the given window to attrs, with color speci-
- fied by pair. X/Open specified an additional parameter
- opts which is unused in all implementations.
+ There are two sets of functions:
- Use attr_get and wattr_get to retrieve attributes for the
- given window.
+ o functions for manipulating the window attributes and color: wat-
+ tr_set and wattr_get.
- Use attr_on and wattr_on to turn on window attributes,
- i.e., values OR'd together in attr, without affecting oth-
- er attributes. Use attr_off and wattr_off to turn off
- window attributes, again values OR'd together in attr,
- without affecting other attributes.
+ o functions for manipulating only the window attributes (not color):
+ wattr_on and wattr_off.
+
+ The wattr_set function sets the current attributes of the given window
+ to attrs, with color specified by pair.
+
+ Use wattr_get to retrieve attributes for the given window.
+
+ Use attr_on and wattr_on to turn on window attributes, i.e., values
+ OR'd together in attr, without affecting other attributes. Use at-
+ tr_off and wattr_off to turn off window attributes, again values OR'd
+ together in attr, without affecting other attributes.
- Most of the window attribute routines are extensions of
- older routines which assume that color pairs are OR'd into
- the attribute parameter. These older routines use the
- same name, omitting an underscore (_).
+ The X/Open window attribute routines which set or get, turn on or off
+ are extensions of older routines which assume that color pairs are OR'd
+ into the attribute parameter. These newer routines use similar names,
+ because X/Open simply added an underscore (_) for the newer names.
+
+ The int datatype used in the legacy routines is treated as if it is the
+ same size as chtype (used by addch(3x)). It holds the common video at-
+ tributes (such as bold, reverse), as well as a few bits for color.
+ Those bits correspond to the A_COLOR symbol. The COLOR_PAIR macro pro-
+ vides a value which can be OR'd into the attribute parameter. For ex-
+ ample, as long as that value fits into the A_COLOR mask, then these
+ calls produce similar results:
+
+ attrset(A_BOLD | COLOR_PAIR(pair));
+ attr_set(A_BOLD, pair, NULL);
+
+ However, if the value does not fit, then the COLOR_PAIR macro uses only
+ the bits that fit. For example, because in ncurses A_COLOR has eight
+ (8) bits, then COLOR_PAIR(259) is 4 (i.e., 259 is 4 more than the limit
+ 255).
+
+ The PAIR_NUMBER macro extracts a pair number from an int (or chtype).
+ For example, the input and output values in these statements would be
+ the same:
+
+ int value = A_BOLD | COLOR_PAIR(input);
+ int output = PAIR_NUMBER(value);
- The attrset routine is a legacy feature predating SVr4
- curses but kept in X/Open Curses for the same reason that
- SVr4 curses kept it: compatibility.
+ The attrset routine is a legacy feature predating SVr4 curses but kept
+ in X/Open Curses for the same reason that SVr4 curses kept it: compati-
+ bility.
- The remaining attr* functions operate exactly like the
- corresponding attr_* functions, except that they take ar-
- guments of type int rather than attr_t.
+ The remaining attr* functions operate exactly like the corresponding
+ attr_* functions, except that they take arguments of type int rather
+ than attr_t.
- There is no corresponding attrget function as such in
- X/Open Curses, although ncurses provides getattrs (see
- curs_legacy(3x)).
+ There is no corresponding attrget function as such in X/Open Curses,
+ although ncurses provides getattrs (see curs_legacy(3x)).
- The routine chgat changes the attributes of a given number
- of characters starting at the current cursor location of
- stdscr. It does not update the cursor and does not per-
- form wrapping. A character count of -1 or greater than
- the remaining window width means to change attributes all
- the way to the end of the current line. The wchgat func-
- tion generalizes this to any window; the mvwchgat function
- does a cursor move before acting.
+ The routine chgat changes the attributes of a given number of charac-
+ ters starting at the current cursor location of stdscr. It does not
+ update the cursor and does not perform wrapping. A character count of
+ -1 or greater than the remaining window width means to change at-
+ tributes all the way to the end of the current line. The wchgat func-
+ tion generalizes this to any window; the mvwchgat function does a cur-
+ sor move before acting.
- In these functions, the color pair argument is a color-
- pair index (as in the first argument of init_pair, see
- curs_color(3x)). The opts argument is not presently used,
- but is reserved for the future (leave it NULL).
+ In these functions, the color pair argument is a color-pair index (as
+ in the first argument of init_pair, see curs_color(3x)).
- The routine color_set sets the current color of the given
- window to the foreground/background combination described
- by the color pair parameter. The parameter opts is re-
- served for future use; applications must supply a null
- pointer.
+ The routine color_set sets the current color of the given window to the
+ foreground/background combination described by the color pair parame-
+ ter.
- The routine standout is the same as attron(A_STANDOUT).
- The routine standend is the same as attrset(A_NORMAL) or
- attrset(0), that is, it turns off all attributes.
+ The routine standout is the same as attron(A_STANDOUT). The routine
+ standend is the same as attrset(A_NORMAL) or attrset(0), that is, it
+ turns off all attributes.
X/Open does not mark these "restricted", because
o they have well established legacy use, and
- o there is no ambiguity about the way the attributes
- might be combined with a color pair.
+ o there is no ambiguity about the way the attributes might be com-
+ bined with a color pair.
- The following video attributes, defined in <curses.h>, can
- be passed to the routines attron, attroff, and attrset, or
- OR'd with the characters passed to addch (see curs_add-
- ch(3x)).
+ The following video attributes, defined in <curses.h>, can be passed to
+ the routines attron, attroff, and attrset, or OR'd with the characters
+ passed to addch (see curs_addch(3x)).
NameDescription
- -----------------------------------------------------------
+ -----------------------------------------------------------------
A_NORMAL Normal display (no highlight)
A_STANDOUT Best highlighting mode of the terminal.
A_UNDERLINE Underlining
@@ -218,10 +241,10 @@
A_ALTCHARSET Alternate character set
A_ITALIC Italics (non-X/Open extension)
A_CHARTEXT Bit-mask to extract a character
+ A_COLOR Bit-mask to extract a color (legacy routines)
- These video attributes are supported by attr_on and relat-
- ed functions (which also support the attributes recognized
- by attron, etc.):
+ These video attributes are supported by attr_on and related functions
+ (which also support the attributes recognized by attron, etc.):
NameDescription
-----------------------------------------
@@ -232,52 +255,199 @@
WA_TOP Top highlight
WA_VERTICAL Vertical highlight
- The return values of many of these routines are not mean-
- ingful (they are implemented as macro-expanded assignments
- and simply return their argument). The SVr4 manual page
- claims (falsely) that these routines always return 1.
+ The return values of many of these routines are not meaningful (they
+ are implemented as macro-expanded assignments and simply return their
+ argument). The SVr4 manual page claims (falsely) that these routines
+ always return 1.
- These functions may be macros: attroff, wattroff, attron,
- wattron, attrset, wattrset, standend and standout.
-
- Color pair values can only be OR'd with attributes if the
- pair number is less than 256. The alternate functions
- such as color_set can pass a color pair value directly.
- However, ncurses ABI 4 and 5 simply OR this value within
- the alternate functions. You must use ncurses ABI 6 to
+ These functions may be macros:
+
+ attroff, wattroff, attron, wattron, attrset, wattrset, standend
+ and standout.
+
+ Color pair values can only be OR'd with attributes if the pair number
+ is less than 256. The alternate functions such as color_set can pass a
+ color pair value directly. However, ncurses ABI 4 and 5 simply OR this
+ value within the alternate functions. You must use ncurses ABI 6 to
support more than 256 color pairs.
+
+ 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, attrset and attr_set
+ 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 standout feature (often implemented as
+ bold and/or reverse video). The BSD curses library provided functions
+ standout and standend 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 A_
+ symbols for use by applications to manipulate the other attributes.
+ There are few useful references for the chronology.
+
+ Goodheart's book UNIXCursesExplained (1991) describes SVr3 (1987),
+ commenting on several functions:
+
+ o the attron, attroff, attrset functions (and most of the functions
+ found in SVr4 but not in BSD curses) were introduced by System V,
+
+ o the alternate character set feature with A_ALTCHARSET was added in
+ SVr2 and improved in SVr3 (by adding acs_map[]),
+
+ ostart_color and related color-functions were introduced by System
+ V.3.2,
+
+ o pads, soft-keys were added in SVr3, and
+
+ Goodheart did not mention the background character or the cchar_t type.
+ Those are respectively SVr4 and X/Open features. He did mention the A_
+ 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
+ chtype for characters and colors, and took into account the different
+ integer sizes (32-bit versus 64-bit).
+
+ This table showing the number of bits for A_COLOR and A_CHARTEXT 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.
+
+ YearSystemArchColorCharNotes
+ ----------------------------------------------------------------
+ 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 chtype
+
+ Notes:
+
+ Regarding HP-UX,
+
+ o HP-UX 10.20 (1996) added support for 64-bit PA-RISC processors
+ in 1996.
+
+ o 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),
+
+ o These used 64-bit hardware. Like ncurses, the OSF/1 curses in-
+ terface is not customized for 32-bit and 64-bit versions.
+
+ o Unlike other systems which evolved from AT&T code, OSF/1 provid-
+ ed a new implementation for X/Open curses.
+
+ Regarding Solaris,
+
+ o The initial release of Solaris was in 1992.
+
+ o The xpg4 (X/Open) curses was developed by MKS from 1990 to 1995.
+ Sun's copyright began in 1996.
+
+ o 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,
+
+ o Development of the curses library began in 1991, stopped in
+ 2000.
+
+ o Color support was added in 1998.
+
+ o The library uses only chtype (no cchar_t).
+
+ Once X/Open curses was adopted in the mid-1990s, the constraint of a
+ 32-bit interface with many colors and wide-characters for chtype became
+ a moot point. The cchar_t structure (whose size and members are not
+ specified in X/Open Curses) could be extended as needed.
+
+ Other interfaces are rarely used now:
+
+ o BSD curses was improved slightly in 1993/1994 using Keith Bostic's
+ modification to make the library 8-bit clean for nvi. He moved
+ standout attribute to a structure member.
+
+ The resulting 4.4BSD curses was replaced by ncurses over the next
+ ten years.
+
+ o U/Win is rarely used now.
+
+
+
+ This implementation provides the A_ITALIC attribute for terminals which
+ have the enter_italics_mode (sitm) and exit_italics_mode (ritm) capa-
+ bilities. Italics are not mentioned in X/Open Curses. Unlike the oth-
+ er video attributes, A_ITALIC is unrelated to the set_attributes capa-
+ bilities. This implementation makes the assumption that exit_at-
+ tribute_mode may also reset italics.
+
+ Each of the functions added by XSI Curses has a parameter opts, which
+ X/Open Curses still (after more than twenty years) documents as re-
+ served for future use, saying that it should be NULL. This implementa-
+ tion uses that parameter in ABI 6 for the functions which have a color-
+ pair parameter to support extendedcolorpairs:
+
+ o For functions which modify the color, e.g., wattr_set, if opts is
+ set it is treated as a pointer to int, and used to set the color
+ pair instead of the shortpair parameter.
+
+ o For functions which retrieve the color, e.g., wattr_get, if opts is
+ set it is treated as a pointer to int, and used to retrieve the
+ color pair as an int value, in addition retrieving it via the stan-
+ dard pointer to short parameter.
+
+ The remaining functions which have opts, but do not manipulate color,
+ e.g., wattr_on and wattr_off are not used by this implementation except
+ to check that they are NULL.
+
+
- These functions are supported in the XSI Curses standard,
- Issue 4. The standard defined the dedicated type for
- highlights, attr_t, which is not defined in SVr4 curses.
- The functions taking attr_t arguments are not supported
- under SVr4.
-
- The XSI Curses standard states that whether the tradition-
- al functions attron/attroff/attrset can manipulate at-
- tributes other than A_BLINK, A_BOLD, A_DIM, A_REVERSE,
- A_STANDOUT, or A_UNDERLINE is "unspecified". Under this
- implementation as well as SVr4 curses, these functions
- correctly manipulate all other highlights (specifically,
- A_ALTCHARSET, A_PROTECT, and A_INVIS).
-
- This implementation provides the A_ITALIC attribute for
- terminals which have the enter_italics_mode (sitm) and ex-
- it_italics_mode (ritm) capabilities. Italics are not men-
- tioned in X/Open Curses. Unlike the other video at-
- tributes, I_ITALIC is unrelated to the set_attributes ca-
- pabilities. This implementation makes the assumption that
- exit_attribute_mode may also reset italics.
-
- XSI Curses added the new entry points, attr_get, attr_on,
- attr_off, attr_set, wattr_on, wattr_off, wattr_get, wat-
- tr_set. These are intended to work with a new series of
- highlight macros prefixed with WA_. The older macros have
- direct counterparts in the newer set of names:
+ These functions are supported in the XSI Curses standard, Issue 4. The
+ standard defined the dedicated type for highlights, attr_t, which was
+ not defined in SVr4 curses. The functions taking attr_t 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 touchwin to force the screen to
+ match the updated attributes.
+
+ The XSI Curses standard states that whether the traditional functions
+ attron/attroff/attrset can manipulate attributes other than A_BLINK,
+ A_BOLD, A_DIM, A_REVERSE, A_STANDOUT, or A_UNDERLINE is "unspecified".
+ Under this implementation as well as SVr4 curses, these functions cor-
+ rectly manipulate all other highlights (specifically, A_ALTCHARSET,
+ A_PROTECT, and A_INVIS).
+
+ XSI Curses added these entry points:
+
+ attr_get, attr_on, attr_off, attr_set, wattr_on, wattr_off, wat-
+ tr_get, wattr_set
+
+ The new functions are intended to work with a new series of highlight
+ macros prefixed with WA_. The older macros have direct counterparts in
+ the newer set of names:
NameDescription
------------------------------------------------------------
@@ -290,24 +460,34 @@
WA_BOLD Extra bright or bold
WA_ALTCHARSET Alternate character set
- Very old versions of this library did not force an update
- of the screen when changing the attributes. Use touchwin
- to force the screen to match the updated attributes.
+ 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.:
- The XSI curses standard specifies that each pair of corre-
- sponding A_ and WA_-using functions operates on the same
- current-highlight information.
+ o The XSI curses standard specifies that each pair of corresponding
+ A_ and WA_-using functions operates on the same current-highlight
+ information.
- The XSI standard extended conformance level adds new high-
- lights A_HORIZONTAL, A_LEFT, A_LOW, A_RIGHT, A_TOP, A_VER-
- TICAL (and corresponding WA_ macros for each). As of Au-
- gust 2013, no known terminal provides these highlights
- (i.e., via the sgr1 capability).
+ o However, in some implementations, those symbols have unrelated val-
+ ues.
+
+ For example, the Solaris xpg4 (X/Open) curses declares attr_t to be
+ an unsigned short integer (16-bits), while chtype is a unsigned in-
+ teger (32-bits). The WA_ symbols in this case are different from
+ the A_ symbols because they are used for a smaller datatype which
+ does not represent A_CHARTEXT or A_COLOR.
+
+ In this implementation (as in many others), the values happen to be
+ the same because it simplifies copying information between chtype
+ and cchar_t variables.
+
+ The XSI standard extended conformance level adds new highlights A_HORI-
+ ZONTAL, A_LEFT, A_LOW, A_RIGHT, A_TOP, A_VERTICAL (and corresponding
+ WA_ macros for each). As of August 2013, no known terminal provides
+ these highlights (i.e., via the sgr1 capability).
- All routines return the integer OK on success, or ERR on
- failure.
+ All routines return the integer OK on success, or ERR on failure.
X/Open does not define any error conditions.
@@ -315,21 +495,24 @@
o returns an error if the window pointer is null.
- o returns an error if the color pair parameter for wcol-
- or_set is outside the range 0..COLOR_PAIRS-1.
+ o returns an error if the color pair parameter for wcolor_set is out-
+ side the range 0..COLOR_PAIRS-1.
+
+ o does not return an error if either of the parameters of wattr_get
+ used for retrieving attribute or color-pair values is NULL.
- Functions with a "mv" prefix first perform a cursor move-
- ment using wmove, and return an error if the position is
- outside the window, or if the window pointer is null.
+ Functions with a "mv" prefix first perform a cursor movement using
+ wmove, and return an error if the position is outside the window, or if
+ the window pointer is null.