- These routines manipulate the current attributes of the
- named window. The current attributes of a window apply to
- all characters that are written into the window with wadd-
- ch, 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
+ 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 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.
-
- The routine attrset sets the current attributes of the
- given window to attrs. The routine attroff turns off the
- named attributes without turning any other attributes on
- or off. The routine attron turns on the named attributes
- without affecting any others. 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 attrset and related routines do not affect the at-
- tributes used when erasing portions of the window. See
- curs_bkgd(3x) for functions which modify the attributes
- used for erasing and clearing.
+
- The attrset routine is actually a legacy feature predating
- SVr4 curses but kept in X/Open Curses for the same reason
- that SVr4 curses kept it: compatbility. The routine at-
- tr_set provides for passing a color-pair parameter.
+ o functions for manipulating the window attributes and color:
+ wattr_set and wattr_get.
- The remaining attr_* functions operate exactly like the
- corresponding attr* functions, except that they take argu-
- ments of type attr_t rather than int.
+ 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.
-
- The routine color_set sets the current color of the given
- window to the foreground/background combination described
- by the color_pair_number. The parameter opts is reserved
- for future use, applications must supply a null pointer.
+ 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
+ attr_off and wattr_off to turn off window attributes, again values OR'd
+ together in attr, without affecting other attributes.
-
- The routine wattr_get returns the current attribute and
- color pair for the given window; attr_get returns the cur-
- rent attribute and color pair for stdscr.
- There is no corresponding attrget function as such in
- X/Open Curses, although ncurses provides getattrs (see
- curs_legacy(3x)).
+
+ 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
+ attributes (such as bold, reverse), as well as a few bits for color.
+ Those bits correspond to the A_COLOR symbol. The COLOR_PAIR macro
+ provides a value which can be OR'd into the attribute parameter. For
+ example, as long as that value fits into the A_COLOR mask, then these
+ calls produce similar results:
-
- 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. In these functions, the
- color argument is a color-pair index (as in the first ar-
- gument of init_pair, see curs_color(3x)). The opts argu-
- ment is not presently used, but is reserved for the future
- (leave it NULL).
+ 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 ncursesA_COLOR has eight
+ (8) bits, then COLOR_PAIR(259) is 4 (i.e., 259 is 4 more than the limit
+ 255).
-
- 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)).
-
- NameDescription
- ------------------------------------------------------------
- A_NORMAL Normal display (no highlight)
- A_STANDOUT Best highlighting mode of the terminal.
- A_UNDERLINE Underlining
- A_REVERSE Reverse video
- A_BLINK Blinking
- A_DIM Half bright
- A_BOLD Extra bright or bold
- A_PROTECT Protected mode
- A_INVIS Invisible or blank mode
- A_ALTCHARSET Alternate character set
- A_ITALIC Italics (non-X/Open extension)
- A_CHARTEXT Bit-mask to extract a character
-
- COLOR_PAIR(n) Color-pair number n
-
- These video attributes are supported by attr_on and relat-
- ed functions (which also support the attributes recognized
- by attron, etc.):
-
- NameDescription
- -----------------------------------------
+ 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 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)).
+
+
+
+ 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 perform 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
+ function generalizes this to any window; the mvwchgat function does a
+ cursor 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 routine color_set sets the current color of the given window to the
+ foreground/background combination described by the color pair
+ parameter.
+
+
+
+ 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 Curses 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.
+
+
+
+ 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
+ A_REVERSE Reverse video
+ A_BLINK Blinking
+ A_DIM Half bright
+ A_BOLD Extra bright or bold
+ A_PROTECT Protected mode
+ A_INVIS Invisible or blank mode
+ 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 related functions
+ (which also support the attributes recognized by attron, etc.):
+
+ NameDescription
+ -----------------------------------------------------------------
WA_HORIZONTAL Horizontal highlight
WA_LEFT Left highlight
WA_LOW Low highlight
@@ -206,114 +232,272 @@
WA_TOP Top highlight
WA_VERTICAL Vertical highlight
- For consistency
+ 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.
- The following macro is the reverse of COLOR_PAIR(n):
- PAIR_NUMBER(attrs) Returns the pair number associated
- with the COLOR_PAIR(n) attribute.
+
+ All routines return the integer OK on success, or ERR on failure.
- 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.
+ X/Open Curses does not specify any error conditions.
+ This implementation
-
- Note that attroff, wattroff, attron, wattron, attrset,
- wattrset, standend and standout may be macros.
-
- 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
+ o returns an error if the window pointer is null.
+
+ o returns an error if the color pair parameter for wcolor_set is
+ outside 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 prefixed with "mv" first perform cursor movement and fail if
+ the position (y, x)
+
+
+
+ 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.
-
- 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:
-
- NameDescription
- ------------------------------------------------------------
+
+ This implementation provides the A_ITALIC attribute for terminals which
+ have the enter_italics_mode (sitm) and exit_italics_mode (ritm)
+ capabilities. Italics are not mentioned in X/Open Curses. Unlike the
+ other video attributes, A_ITALIC is unrelated to the set_attributes
+ capabilities. This implementation makes the assumption that
+ exit_attribute_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
+ reserved for future use, saying that it should be NULL. This
+ implementation 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 and wattr_on,
+ 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 to retrieving it via the
+ standard pointer to short parameter.
+
+ o For functions which turn attributes off, e.g., wattr_off, the opts
+ parameter is ignored except except to check that it is NULL.
+
+
+
+ These functions are described in X/Open Curses, 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.
+
+ X/Open Curses 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
+ correctly manipulate all other highlights (specifically, A_ALTCHARSET,
+ A_PROTECT, and A_INVIS).
+
+ X/Open Curses added these entry points:
+
+ attr_get, attr_on, attr_off, attr_set, wattr_on, wattr_off,
+ wattr_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
+ -----------------------------------------------------------------
WA_NORMAL Normal display (no highlight)
- WA_STANDOUT Best highlighting mode of the terminal.
+ WA_STANDOUT Best highlighting mode of the terminal
WA_UNDERLINE Underlining
WA_REVERSE Reverse video
WA_BLINK Blinking
WA_DIM Half bright
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.
+ X/Open 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.:
+
+ o X/Open Curses specifies that each pair of corresponding A_ and
+ WA_-using functions operates on the same current-highlight
+ information.
+
+ o However, in some implementations, those symbols have unrelated
+ values.
+
+ For example, the Solaris xpg4 (X/Open) curses declares attr_t to be
+ an unsigned short integer (16-bits), while chtype is a unsigned
+ integer (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 curses standard specifies that each pair of corre-
- sponding A_ and WA_-using functions operates on the same
- current-highlight information.
+ o Because ncurses's attr_t can hold a color pair (in the A_COLOR
+ field), a call to wattr_on, wattr_off, or wattr_set may alter the
+ window's color. If the color pair information in the attribute
+ parameter is zero, no change is made to the window's color.
- 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).
+ This is consistent with SVr4 curses; X/Open Curses does not specify
+ this.
+ The X/Open Curses extended conformance level adds new highlights
+ A_HORIZONTAL, 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).
-
+ X/Open Curses is largely based on SVr4 curses, adding support for
+ "wide-characters" (not specific to Unicode). Some of the X/Open
+ differences from SVr4 curses address the way video attributes can be
+ applied 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.
- This implementation returns an error if the window pointer
- is null. The wcolor_set function returns an error if the
- color pair parameter is outside the range 0..COL-
- OR_PAIRS-1. This implementation also provides getattrs
- for compatibility with older versions of curses.
+ 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.
- 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.
+ Some terminals in the 1980s could support a variety of video
+ attributes, 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:
-
- curses(3x), curs_addch(3x), curs_addstr(3x),
- curs_bkgd(3x), curs_printw(3x), curs_variables(3x)
+ 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
+ alternate character set implementation. A 32-bit library can be used
+ on a 64-bit system, but not necessarily the reverse.
+ Bits
+ YearSystemArchColorCharNotes
+ ------------------------------------------------------------------------
+ 1992 Solaris 5.2 32 6 17 SVr4 curses
+ 1992 HP-UX 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:
- curs_attr(3x)
+ 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
+ interface is not customized for 32-bit and 64-bit versions.
+
+ o Unlike other systems which evolved from AT&T code, OSF/1
+ provided 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
+ interface.
+
+ 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(1). 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.
+
+
+