|
NAME | SYNOPSIS | DESCRIPTION | VIDEO ATTRIBUTES | NOTES | HISTORY | EXTENSIONS | PORTABILITY | RETURN VALUE | SEE ALSO | COLOPHON |
|
curs_attr(3X) curs_attr(3X)
attr_get, wattr_get, attr_set, wattr_set, attr_off, wattr_off,
attr_on, wattr_on, attroff, wattroff, attron, wattron, attrset,
wattrset, chgat, wchgat, mvchgat, mvwchgat, color_set, wcolor_set,
standend, wstandend, standout, wstandout - curses character and
window attribute control routines
#include <curses.h>
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.
Window attributes
There are two sets of functions:
· functions for manipulating the window attributes and color:
wattr_set and wattr_get.
· 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.
Legacy window attributes
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:
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 (259-255).
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 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)).
Change character rendition
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)).
Change window color
The routine color_set sets the current color of the given window to
the foreground/background combination described by the color pair
parameter.
Standout
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
· they have well established legacy use, and
· 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)).
Name Description
─────────────────────────────────────────────────────────────────
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.):
Name Description
─────────────────────────────────────────
WA_HORIZONTAL Horizontal highlight
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.
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
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.
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:
· the attron, attroff, attrset functions (and most of the functions
found in SVr4 but not in BSD curses) were introduced by System V,
· the alternate character set feature with A_ALTCHARSET was added
in SVr2 and improved in SVr3 (by adding acs_map[]),
· start_color and related color-functions were introduced by System
V.3.2,
· 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 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,
· HP-UX 10.20 (1996) added support for 64-bit PA-RISC processors
in 1996.
· 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),
· These used 64-bit hardware. Like ncurses, the OSF/1 curses
interface is not customized for 32-bit and 64-bit versions.
· Unlike other systems which evolved from AT&T code, OSF/1
provided a new implementation for X/Open curses.
Regarding Solaris,
· The initial release of Solaris was in 1992.
· The xpg4 (X/Open) curses was developed by MKS from 1990 to
1995. Sun's copyright began in 1996.
· 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,
· Development of the curses library began in 1991, stopped in
2000.
· Color support was added in 1998.
· 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:
· 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.
· 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)
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:
· 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.
· 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.
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 correctly 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,
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:
Name Description
────────────────────────────────────────────────────────────
WA_NORMAL Normal display (no highlight)
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.:
· The XSI curses standard specifies that each pair of corresponding
A_ and WA_-using functions operates on the same current-highlight
information.
· 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 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).
All routines return the integer OK on success, or ERR on failure.
X/Open does not define any error conditions.
This implementation
· returns an error if the window pointer is null.
· returns an error if the color pair parameter for wcolor_set is
outside the range 0..COLOR_PAIRS-1.
· 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.
curses(3X), curs_addch(3X), curs_addstr(3X), curs_bkgd(3X),
curs_printw(3X), curs_variables(3X)
This page is part of the ncurses (new curses) project. Information
about the project can be found at
⟨https://www.gnu.org/software/ncurses/ncurses.html⟩. If you have a
bug report for this manual page, send it to
bug-ncurses-request@gnu.org. This page was obtained from the
project's upstream Git mirror of the CVS repository
⟨git://ncurses.scripts.mit.edu/ncurses.git⟩ on 2018-02-02. (At that
time, the date of the most recent commit that was found in the repos‐
itory was 2018-01-30.) If you discover any rendering problems in
this HTML version of the page, or you believe there is a better or
more up-to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not part
of the original manual page), send a mail to man-pages@man7.org
curs_attr(3X)
|
HTML rendering created 2018-02-02 by Michael Kerrisk, author of The Linux Programming Interface, maintainer of the Linux man-pages project. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH.
|
|