int attr_get(attr_t *attrs, short *pair, void *opts);
int wattr_get(WINDOW *win, attr_t *attrs, short *pair, void *opts);
int attr_set(attr_t attrs, short pair, void *opts);
int wattr_set(WINDOW *win, attr_t attrs, short pair, void *opts);
int attr_off(attr_t attrs, void *opts);
int wattr_off(WINDOW *win, attr_t attrs, void *opts);
int attr_on(attr_t attrs, void *opts);
int wattr_on(WINDOW *win, attr_t attrs, void *opts);
int attroff(int attrs);
int wattroff(WINDOW *win, int attrs);
int attron(int attrs);
int wattron(WINDOW *win, int attrs);
int attrset(int attrs);
int wattrset(WINDOW *win, int attrs);
int chgat(int n, attr_t attr, short pair, const void *opts);
int wchgat(WINDOW *win,
int n, attr_t attr, short pair, const void *opts);
int mvchgat(int y, int x,
int n, attr_t attr, short pair, const void *opts);
int mvwchgat(WINDOW *win, int y, int x,
int n, attr_t attr, short pair, const void *opts);
int color_set(short pair, void* opts);
int wcolor_set(WINDOW *win, short pair, void* opts);
int standend(void);
int wstandend(WINDOW *win);
int standout(void);
int wstandout(WINDOW *win);
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.
Routines which do not have a WINDOW* parameter apply to stdscr. For example, attr_set is the stdscr variant of wattr_set.
There are two sets of functions:
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functions for manipulating the window attributes and color:
wattr_set and wattr_get.
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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 attr_off and wattr_off to turn off window attributes, again values OR'd together in attr, without affecting other attributes.
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:
.sp
.in +4
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:
.sp
.in +4
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 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
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they have well established legacy use, and
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there is no ambiguity about the way the attributes
might be combined with a color pair.
| Name | Description | |
| 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.):
| Name | Description | |
| WA_LEFT | Left highlight | |
| WA_LOW | Low highlight | |
| WA_RIGHT | Right highlight | |
| WA_TOP | Top highlight | |
| WA_VERTICAL | Vertical highlight |
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.
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.
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 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
UNIX Curses Explained (1991) describes SVr3 (1987),
commenting on several functions:
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the attron, attroff, attrset functions
(and most of the functions found in SVr4 but not in BSD curses) were
introduced by System V,
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the alternate character set feature with A_ALTCHARSET was
added in SVr2 and improved in SVr3 (by adding acs_map[]),
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start_color and related color-functions were introduced by System V.3.2,
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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.
| Year | System | Arch | Color | Char | Notes |
| 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,
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HP-UX 10.20 (1996) added support for 64-bit PA-RISC processors in 1996.
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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),
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These used 64-bit hardware.
Like ncurses, the OSF/1 curses interface is not customized for 32-bit
and 64-bit versions.
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Unlike other systems which evolved from AT&T code,
OSF/1 provided a new implementation for X/Open curses.
Regarding Solaris,
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The initial release of Solaris was in 1992.
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The xpg4 (X/Open) curses was developed by MKS from 1990 to 1995.
Sun's copyright began in 1996.
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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,
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Development of the curses library began in 1991, stopped in 2000.
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Color support was added in 1998.
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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:
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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.
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 extended color pairs:
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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 short pair parameter.
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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 standard 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.
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 correctly manipulate all other highlights (specifically, A_ALTCHARSET, A_PROTECT, and A_INVIS).
XSI Curses added these entry points:
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:
| Name | Description | |
| 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 |
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.:
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The XSI curses standard specifies that each pair of corresponding A_
and WA_-using functions operates on the same current-highlight
information.
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However, in some implementations, those symbols have unrelated values.
The XSI standard 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 does not define any error conditions.
This implementation
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returns an error if the window pointer is null.
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returns an error if the color pair parameter
for wcolor_set is outside the range 0..COLOR_PAIRS-1.
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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 movement using wmove, and return an error if the position is outside the window, or if the window pointer is null.