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<H1 class="no-header">curs_attr 3x 2025-11-11 ncurses 6.6 Library calls</H1>
<PRE>
<STRONG><A HREF="curs_attr.3x.html">curs_attr(3x)</A></STRONG> Library calls <STRONG><A HREF="curs_attr.3x.html">curs_attr(3x)</A></STRONG>
</PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
<STRONG>attr_get</STRONG>, <STRONG>wattr_get</STRONG>, <STRONG>attr_set</STRONG>, <STRONG>wattr_set</STRONG>, <STRONG>attr_off</STRONG>, <STRONG>wattr_off</STRONG>, <STRONG>attr_on</STRONG>,
<STRONG>wattr_on</STRONG>, <STRONG>attroff</STRONG>, <STRONG>wattroff</STRONG>, <STRONG>attron</STRONG>, <STRONG>wattron</STRONG>, <STRONG>attrset</STRONG>, <STRONG>wattrset</STRONG>, <STRONG>chgat</STRONG>,
<STRONG>wchgat</STRONG>, <STRONG>mvchgat</STRONG>, <STRONG>mvwchgat</STRONG>, <STRONG>color_set</STRONG>, <STRONG>wcolor_set</STRONG>, <STRONG>standend</STRONG>, <STRONG>wstandend</STRONG>,
<STRONG>standout</STRONG>, <STRONG>wstandout</STRONG> - manipulate attributes of character cells in
<EM>curses</EM> windows
</PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
<STRONG>#include</STRONG> <STRONG><curses.h></STRONG>
<STRONG>int</STRONG> <STRONG>attr_get(attr_t</STRONG> <STRONG>*</STRONG><EM>attrs</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <STRONG>*</STRONG><EM>pair</EM><STRONG>,</STRONG> <STRONG>void</STRONG> <STRONG>*</STRONG><EM>opts</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>wattr_get(WINDOW</STRONG> <STRONG>*</STRONG><EM>win</EM><STRONG>,</STRONG> <STRONG>attr_t</STRONG> <STRONG>*</STRONG><EM>attrs</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <STRONG>*</STRONG><EM>pair</EM><STRONG>,</STRONG> <STRONG>void</STRONG> <STRONG>*</STRONG><EM>opts</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>attr_set(attr_t</STRONG> <EM>attrs</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <EM>pair</EM><STRONG>,</STRONG> <STRONG>void</STRONG> <STRONG>*</STRONG><EM>opts</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>wattr_set(WINDOW</STRONG> <STRONG>*</STRONG><EM>win</EM><STRONG>,</STRONG> <STRONG>attr_t</STRONG> <EM>attrs</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <EM>pair</EM><STRONG>,</STRONG> <STRONG>void</STRONG> <STRONG>*</STRONG><EM>opts</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>attr_off(attr_t</STRONG> <EM>attrs</EM><STRONG>,</STRONG> <STRONG>void</STRONG> <STRONG>*</STRONG><EM>opts</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>wattr_off(WINDOW</STRONG> <STRONG>*</STRONG><EM>win</EM><STRONG>,</STRONG> <STRONG>attr_t</STRONG> <EM>attrs</EM><STRONG>,</STRONG> <STRONG>void</STRONG> <STRONG>*</STRONG><EM>opts</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>attr_on(attr_t</STRONG> <EM>attrs</EM><STRONG>,</STRONG> <STRONG>void</STRONG> <STRONG>*</STRONG><EM>opts</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>wattr_on(WINDOW</STRONG> <STRONG>*</STRONG><EM>win</EM><STRONG>,</STRONG> <STRONG>attr_t</STRONG> <EM>attrs</EM><STRONG>,</STRONG> <STRONG>void</STRONG> <STRONG>*</STRONG><EM>opts</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>attroff(int</STRONG> <EM>attrs</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>wattroff(WINDOW</STRONG> <STRONG>*</STRONG><EM>win</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>attrs</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>attron(int</STRONG> <EM>attrs</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>wattron(WINDOW</STRONG> <STRONG>*</STRONG><EM>win</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>attrs</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>attrset(int</STRONG> <EM>attrs</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>wattrset(WINDOW</STRONG> <STRONG>*</STRONG><EM>win</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>attrs</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>chgat(int</STRONG> <EM>n</EM><STRONG>,</STRONG> <STRONG>attr_t</STRONG> <EM>attr</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <EM>pair</EM><STRONG>,</STRONG> <STRONG>const</STRONG> <STRONG>void</STRONG> <STRONG>*</STRONG><EM>opts</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>wchgat(WINDOW</STRONG> <STRONG>*</STRONG><EM>win</EM><STRONG>,</STRONG>
<STRONG>int</STRONG> <EM>n</EM><STRONG>,</STRONG> <STRONG>attr_t</STRONG> <EM>attr</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <EM>pair</EM><STRONG>,</STRONG> <STRONG>const</STRONG> <STRONG>void</STRONG> <STRONG>*</STRONG><EM>opts</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>mvchgat(int</STRONG> <EM>y</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>x</EM><STRONG>,</STRONG>
<STRONG>int</STRONG> <EM>n</EM><STRONG>,</STRONG> <STRONG>attr_t</STRONG> <EM>attr</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <EM>pair</EM><STRONG>,</STRONG> <STRONG>const</STRONG> <STRONG>void</STRONG> <STRONG>*</STRONG><EM>opts</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>mvwchgat(WINDOW</STRONG> <STRONG>*</STRONG><EM>win</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>y</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>x</EM><STRONG>,</STRONG>
<STRONG>int</STRONG> <EM>n</EM><STRONG>,</STRONG> <STRONG>attr_t</STRONG> <EM>attr</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <EM>pair</EM><STRONG>,</STRONG> <STRONG>const</STRONG> <STRONG>void</STRONG> <STRONG>*</STRONG><EM>opts</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>color_set(short</STRONG> <EM>pair</EM><STRONG>,</STRONG> <STRONG>void*</STRONG> <EM>opts</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>wcolor_set(WINDOW</STRONG> <STRONG>*</STRONG><EM>win</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <EM>pair</EM><STRONG>,</STRONG> <STRONG>void*</STRONG> <EM>opts</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>standend(void);</STRONG>
<STRONG>int</STRONG> <STRONG>wstandend(WINDOW</STRONG> <STRONG>*</STRONG><EM>win</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>standout(void);</STRONG>
<STRONG>int</STRONG> <STRONG>wstandout(WINDOW</STRONG> <STRONG>*</STRONG><EM>win</EM><STRONG>);</STRONG>
</PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
These routines manipulate the current attributes of the named window,
which then apply to all characters that are written into the window
with <STRONG>waddch</STRONG>, <STRONG>waddstr</STRONG> and <STRONG>wprintw</STRONG>. 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 <STRONG><A HREF="curs_bkgd.3x.html">curs_bkgd(3x)</A></STRONG> for functions which modify the
attributes used for erasing and clearing.
</PRE><H3><a name="h3-Window-Attributes">Window Attributes</a></H3><PRE>
There are two sets of functions:
<STRONG>o</STRONG> functions for manipulating the window attributes and color:
<STRONG>wattr_set</STRONG> and <STRONG>wattr_get</STRONG>.
<STRONG>o</STRONG> functions for manipulating only the window attributes (not color):
<STRONG>wattr_on</STRONG> and <STRONG>wattr_off</STRONG>.
The <STRONG>wattr_set</STRONG> function sets the current attributes of the given window
to <EM>attrs</EM>, with color specified by <EM>pair</EM>.
Use <STRONG>wattr_get</STRONG> to retrieve attributes for the given window.
Use <STRONG>attr_on</STRONG> and <STRONG>wattr_on</STRONG> to turn on window attributes, i.e., values
logically "or"-ed together in <EM>attr</EM>, without affecting other attributes.
Use <STRONG>attr_off</STRONG> and <STRONG>wattr_off</STRONG> to turn off window attributes, again values
logically "or"-ed together in <EM>attr</EM>, without affecting other attributes.
</PRE><H3><a name="h3-Legacy-Window-Attributes">Legacy Window Attributes</a></H3><PRE>
The X/Open window attribute routines which <EM>set</EM> or <EM>get</EM>, turn <EM>on</EM> or <EM>off</EM>
are extensions of older routines which assume that color pairs are
logically "or"-ed into the attribute parameter. These newer routines
use similar names, because X/Open simply added an underscore (<STRONG>_</STRONG>) for
the newer names.
The <EM>int</EM> datatype used in the legacy routines is treated as if it is the
same size as <EM>chtype</EM> (used by <STRONG><A HREF="curs_addch.3x.html">addch(3x)</A></STRONG>). It holds the common video
attributes (such as bold, reverse), as well as a few bits for color.
Those bits correspond to the <STRONG>A_COLOR</STRONG> symbol. The <STRONG>COLOR_PAIR</STRONG> macro
provides a value which can be logically "or"-ed into the attribute
parameter. For example, as long as that value fits into the <STRONG>A_COLOR</STRONG>
mask, then these calls produce similar results:
attrset(A_BOLD | COLOR_PAIR(<EM>pair</EM>));
attr_set(A_BOLD, <EM>pair</EM>, NULL);
However, if the value does not fit, then the <STRONG>COLOR_PAIR</STRONG> macro uses only
the bits that fit. For example, because in <EM>ncurses</EM> <STRONG>A_COLOR</STRONG> has eight
(8) bits, then <STRONG>COLOR_PAIR(</STRONG><EM>259</EM><STRONG>)</STRONG> is 4 (i.e., 259 is 4 more than the limit
255).
The <STRONG>PAIR_NUMBER</STRONG> macro extracts a pair number from an <EM>int</EM> (or <EM>chtype</EM>).
For example, the <EM>input</EM> and <EM>output</EM> values in these statements would be
the same:
int value = A_BOLD | COLOR_PAIR(<EM>input</EM>);
int <EM>output</EM> = PAIR_NUMBER(value);
The <STRONG>attrset</STRONG> routine is a legacy feature predating SVr4 <EM>curses</EM> but kept
in X/Open Curses for the same reason that SVr4 <EM>curses</EM> kept it:
compatibility.
The remaining <STRONG>attr</STRONG>* functions operate exactly like the corresponding
<STRONG>attr_</STRONG>* functions, except that they take arguments of type <EM>int</EM> rather
than <EM>attr</EM><STRONG>_</STRONG><EM>t</EM>.
There is no corresponding <STRONG>attrget</STRONG> function as such in X/Open Curses,
although <EM>ncurses</EM> provides <STRONG>getattrs</STRONG> (see <STRONG><A HREF="curs_legacy.3x.html">curs_legacy(3x)</A></STRONG>).
</PRE><H3><a name="h3-Change-Character-Rendition">Change Character Rendition</a></H3><PRE>
The routine <STRONG>chgat</STRONG> changes the attributes of a given number of
characters starting at the current cursor location of <STRONG>stdscr</STRONG>. 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 <STRONG>wchgat</STRONG>
function generalizes this to any window; the <STRONG>mvwchgat</STRONG> function does a
cursor move before acting.
In these functions, the color <EM>pair</EM> argument is a color pair index (as
in the first argument of <STRONG>init_pair</STRONG>, see <STRONG><A HREF="curs_color.3x.html">curs_color(3x)</A></STRONG>).
</PRE><H3><a name="h3-Change-Window-Color">Change Window Color</a></H3><PRE>
The routine <STRONG>color_set</STRONG> sets the current color of the given window to the
foreground/background combination described by the color <EM>pair</EM>
parameter.
</PRE><H3><a name="h3-Standout">Standout</a></H3><PRE>
The routine <STRONG>standout</STRONG> is the same as <STRONG>attron(A_STANDOUT)</STRONG>. The routine
<STRONG>standend</STRONG> is the same as <STRONG>attrset(A_NORMAL)</STRONG> or <STRONG>attrset(0)</STRONG>, that is, it
turns off all attributes.
X/Open Curses does not mark these "restricted", because
<STRONG>o</STRONG> they have well established legacy use, and
<STRONG>o</STRONG> there is no ambiguity about the way the attributes might be
combined with a color pair.
</PRE><H3><a name="h3-Video-Attributes">Video Attributes</a></H3><PRE>
The following video attributes, defined in <EM>curses.h</EM>, can be passed to
<STRONG>attron</STRONG>, <STRONG>attroff</STRONG>, <STRONG>attrset</STRONG>, and logically "or"-ed with characters passed
to <STRONG><A HREF="curs_addch.3x.html">addch(3x)</A></STRONG>.
<STRONG>Name</STRONG> <STRONG>Description</STRONG>
-----------------------------------------------------------------
<STRONG>A_NORMAL</STRONG> Normal display (no highlight)
<STRONG>A_STANDOUT</STRONG> Best highlighting mode available
<STRONG>A_UNDERLINE</STRONG> Underlining
<STRONG>A_REVERSE</STRONG> Reverse video
<STRONG>A_BLINK</STRONG> Blinking
<STRONG>A_DIM</STRONG> Half bright
<STRONG>A_BOLD</STRONG> Extra bright or bold
<STRONG>A_PROTECT</STRONG> Protected mode
<STRONG>A_INVIS</STRONG> Invisible or blank mode
<STRONG>A_ALTCHARSET</STRONG> Alternate character set
<STRONG>A_ITALIC</STRONG> Italics (non-X/Open extension)
<STRONG>A_ATTRIBUTES</STRONG> Mask to extract character code
<STRONG>A_CHARTEXT</STRONG> Mask to extract attributes
<STRONG>A_COLOR</STRONG> Mask to extract color pair identifier
<STRONG>attr_on</STRONG>, <STRONG>attr_off</STRONG>, and <STRONG>attr_set</STRONG> support the foregoing as well as the
following additional attributes.
<STRONG>Name</STRONG> <STRONG>Description</STRONG>
-----------------------------------------------------------------
<STRONG>WA_HORIZONTAL</STRONG> Horizontal highlight
<STRONG>WA_LEFT</STRONG> Left highlight
<STRONG>WA_LOW</STRONG> Low highlight
<STRONG>WA_RIGHT</STRONG> Right highlight
<STRONG>WA_TOP</STRONG> Top highlight
<STRONG>WA_VERTICAL</STRONG> Vertical highlight
</PRE><H2><a name="h2-RETURN-VALUE">RETURN VALUE</a></H2><PRE>
These functions return <STRONG>OK</STRONG> on success and <STRONG>ERR</STRONG> on failure.
In <EM>ncurses</EM>, they return <STRONG>ERR</STRONG> if <EM>win</EM> is <EM>NULL</EM>.
<STRONG>wcolor_set</STRONG> returns <STRONG>ERR</STRONG> if <EM>pair</EM> is outside the range <STRONG>0</STRONG>..<STRONG>COLOR_PAIRS-1</STRONG>.
<STRONG>wattr_get</STRONG> does <EM>not</EM> fail if its <EM>attrs</EM> or <EM>pair</EM> parameter is <EM>NULL</EM>.
Functions prefixed with "mv" first perform cursor movement and fail if
the position (<EM>y</EM>, <EM>x</EM>) is outside the window boundaries.
</PRE><H2><a name="h2-NOTES">NOTES</a></H2><PRE>
<STRONG>attr_on</STRONG>, <STRONG>attr_off</STRONG>, <STRONG>attr_set</STRONG>, <STRONG>wattr_set</STRONG>, <STRONG>chgat</STRONG>, <STRONG>mvchgat</STRONG>, <STRONG>mvwchgat</STRONG>,
<STRONG>wchgat</STRONG>, and <STRONG>color_set</STRONG> are part of <EM>ncurses</EM>'s wide-character API, and are
not available in its non-wide-character configuration.
<STRONG>attron</STRONG>, <STRONG>wattron</STRONG>, <STRONG>attroff</STRONG>, <STRONG>wattroff</STRONG>, <STRONG>attrset</STRONG>, <STRONG>wattrset</STRONG>, <STRONG>standout</STRONG>, and
<STRONG>standend</STRONG> may be implemented as macros.
Color pair values may be logically "or"-ed with attributes if the pair
number is less than 256. The alternate functions such as <STRONG>color_set</STRONG> can
pass a color pair value directly. However, <EM>ncurses</EM> ABI 4 and 5 simply
logically "or" this value within the alternate functions. You must use
<EM>ncurses</EM> ABI 6 to support more than 256 color pairs.
</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>)
capabilities. Italics are not mentioned in X/Open Curses. Unlike the
other video attributes, <STRONG>A_ITALIC</STRONG> is unrelated to the <STRONG>set_attributes</STRONG>
capabilities. This implementation makes the assumption that
<STRONG>exit_attribute_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
reserved for future use, saying that it should be <EM>NULL</EM>. This
implementation 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> and <STRONG>wattr_on</STRONG>,
if <EM>opts</EM> is set it is treated as a pointer to <EM>int</EM>, and used to set
the color pair instead of the <EM>short</EM> <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 <EM>int</EM>, and used to retrieve the
color pair as an <EM>int</EM> value, in addition to retrieving it via the
standard pointer to <EM>short</EM> parameter.
<STRONG>o</STRONG> For functions which turn attributes off, e.g., <STRONG>wattr_off</STRONG>, the <EM>opts</EM>
parameter is ignored except to check that it is <EM>NULL</EM>.
</PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
These functions are described in X/Open Curses Issue 4. It specifies
no error conditions for them.
The standard defined the dedicated type for highlights, <EM>attr</EM><STRONG>_</STRONG><EM>t</EM>, which
was not defined in SVr4 <EM>curses</EM>. The functions taking <EM>attr</EM><STRONG>_</STRONG><EM>t</EM> arguments
were not supported under SVr4.
SVr4 describes the functions not taking <EM>attr</EM><STRONG>_</STRONG><EM>t</EM> or <EM>pair</EM> arguments as
always returning <STRONG>1</STRONG>.
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.
X/Open Curses 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 <EM>curses</EM>, these functions
correctly manipulate all other highlights (specifically, <STRONG>A_ALTCHARSET</STRONG>,
<STRONG>A_PROTECT</STRONG>, and <STRONG>A_INVIS</STRONG>).
X/Open 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>wattr_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:
<STRONG>Name</STRONG> <STRONG>Description</STRONG>
-------------------------------------------------
<STRONG>WA_NORMAL</STRONG> Normal display (no highlight)
<STRONG>WA_STANDOUT</STRONG> Best highlighting mode available
<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
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.:
<STRONG>o</STRONG> X/Open Curses 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
values.
For example, the Solaris <EM>xpg4</EM> (X/Open) <EM>curses</EM> declares <EM>attr</EM><STRONG>_</STRONG><EM>t</EM> to be
an unsigned short integer (16-bits), while <EM>chtype</EM> is a unsigned
integer (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 <EM>chtype</EM>
and <EM>cchar</EM><STRONG>_</STRONG><EM>t</EM> variables.
<STRONG>o</STRONG> Because <EM>ncurses</EM>'s <EM>attr</EM><STRONG>_</STRONG><EM>t</EM> can hold a color pair (in the <STRONG>A_COLOR</STRONG>
field), a call to <STRONG>wattr_on</STRONG>, <STRONG>wattr_off</STRONG>, or <STRONG>wattr_set</STRONG> 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.
This is consistent with SVr4 <EM>curses</EM>; X/Open Curses does not specify
this.
The X/Open Curses extended conformance level adds new highlights
<STRONG>A_HORIZONTAL</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-HISTORY">HISTORY</a></H2><PRE>
4BSD (1980) used a <EM>char</EM> to represent each cell of the terminal screen.
It assumed 7-bit character codes, employing the eighth bit of a byte to
represent a <EM>standout</EM> attribute (often implemented as bold and/or
reverse video). It introduced <EM>standout</EM>, <EM>standend</EM>, <EM>wstandout</EM>, and
<EM>wstandend</EM> functions to manipulate this bit. Despite their
inflexibility, they carried over into System V <EM>curses</EM> and ultimately
X/Open Curses due to their pervasive use in legacy applications. While
some 1980s terminals supported a variety of video attributes, BSD
<EM>curses</EM> could do nothing with them.
SVr2 (1984) provided an improved <EM>curses</EM> library, introducing <EM>chtype</EM> to
create the abstract notion of a <EM>curses</EM> character; this was by default
an <EM>unsigned</EM> <EM>short</EM>, with a provision for compile-time redefinition to
other integral types (a freedom not necessarily available to users of
shared libraries, and in any event a source license was necessary to
exercise it). It added the functions <EM>attron</EM>, <EM>attroff</EM>, <EM>attrset</EM>,
<EM>wattron</EM>, <EM>wattroff</EM>, and <EM>wattrset</EM>, and defined the <EM>A</EM><STRONG>_</STRONG> macros listed above
(except for <EM>A</EM><STRONG>_</STRONG><EM>ITALIC</EM> and <EM>A</EM><STRONG>_</STRONG><EM>COLOR</EM>) for use by applications to manipulate
other attributes. The values of these macros were not necessarily the
same in different systems, even among those certified as System V.
SVr3.2 (1988) added the <EM>A</EM><STRONG>_</STRONG><EM>COLOR</EM> macro along with a color system; see
<STRONG><A HREF="curs_color.3x.html">curs_color(3x)</A></STRONG>.
X/Open Curses Issue 4 (1995) is largely based on SVr4 <EM>curses</EM>, but
recognized that the <EM>wchar</EM><STRONG>_</STRONG><EM>t</EM> type of ISO C95 was intended to house only
a single character code, not a sequence of codes combining with a base
character, let alone could it reliably offer room for a color pair
identifier and a set of attribute bits with a potential for further
growth -- thus the standard invented the <EM>curses</EM> complex character type
<EM>cchar</EM><STRONG>_</STRONG><EM>t</EM> and a separate type <EM>attr</EM><STRONG>_</STRONG><EM>t</EM> for storage of attribute bits. The
new types brought along several new functions to manipulate them, some
corresponding to existing <EM>chtype</EM>-based functions (<EM>attr</EM><STRONG>_</STRONG><EM>on</EM>, <EM>attr</EM><STRONG>_</STRONG><EM>off</EM>,
<EM>attr</EM><STRONG>_</STRONG><EM>set</EM>, <EM>wattr</EM><STRONG>_</STRONG><EM>on</EM>, <EM>wattr</EM><STRONG>_</STRONG><EM>off</EM>, and <EM>wattr</EM><STRONG>_</STRONG><EM>set</EM>), and some new (<EM>chgat</EM> and
its variants, <EM>color</EM><STRONG>_</STRONG><EM>set</EM>, and <EM>wcolor</EM><STRONG>_</STRONG><EM>set</EM>).
Different Unix systems used differently sized bit fields in <EM>chtype</EM> for
the character code and the color pair identifier, and took into account
platforms' different integer sizes (32- versus 64-bit).
The following table showing the number of bits for <EM>A</EM><STRONG>_</STRONG><EM>COLOR</EM> and
<EM>A</EM><STRONG>_</STRONG><EM>CHARTEXT</EM> was gleaned from the <EM>curses</EM> 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
converse.
<STRONG>Bits</STRONG>
<STRONG>Year</STRONG> <STRONG>System</STRONG> <STRONG>Arch</STRONG> <STRONG>Color</STRONG> <STRONG>Char</STRONG> <STRONG>Notes</STRONG>
------------------------------------------------------------------------
1992 Solaris 5.2 32 6 17 SVr4 <EM>curses</EM>
1992 HP-UX 9 32 no 8 SVr2 <EM>curses</EM>
1992 AIX 3.2 32 no 23 SVr2 <EM>curses</EM>
1994 OSF/1 r3 32 no 23 SVr2 <EM>curses</EM>
1995 HP-UX 10.00 32 6 16 SVr3 <EM>curses</EM><STRONG>_</STRONG><EM>colr</EM>
1995 HP-UX 10.00 32 6 8 SVr4, X/Open <EM>curses</EM>
1995 Solaris 5.4 32/64 7 16 X/Open <EM>curses</EM>
1996 AIX 4.2 32 7 16 X/Open <EM>curses</EM>
1996 OSF/1 r4 32 6 16 X/Open <EM>curses</EM>
1997 HP-UX 11.00 32 6 8 X/Open <EM>curses</EM>
2000 UWIN 32/64 7/31 16 uses <EM>chtype</EM>
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 <EM>curses</EM> was dropped with HP-UX 11.30 in 2006.
Regarding OSF/1 (and Tru64),
<STRONG>o</STRONG> These used 64-bit hardware. Like <EM>ncurses</EM>, the OSF/1 <EM>curses</EM>
interface is not customized for 32-bit and 64-bit versions.
<STRONG>o</STRONG> Unlike other systems which evolved from AT&T code, OSF/1
provided a new implementation for X/Open Curses.
Regarding Solaris,
<STRONG>o</STRONG> The initial release of Solaris was in 1992.
<STRONG>o</STRONG> Its XPG4 (X/Open Curses-conforming) <EM>xcurses</EM> library was
developed by Mortice Kern Systems 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 <EM>curses</EM>
interface.
Regarding UWIN,
<STRONG>o</STRONG> Development of the <EM>curses</EM> library began in 1991, stopped in
2000.
<STRONG>o</STRONG> Color support was added in 1998.
<STRONG>o</STRONG> The library uses only <EM>chtype</EM> (not <EM>cchar</EM><STRONG>_</STRONG><EM>t</EM>).
Once X/Open Curses was adopted in the mid-1990s, the constraint of a
32-bit interface with many colors and wide-characters for <EM>chtype</EM> became
a moot point. The <EM>cchar</EM><STRONG>_</STRONG><EM>t</EM> 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 <EM>curses</EM> was improved slightly in 1993/1994 using Keith Bostic's
modification to make the library 8-bit clean for <STRONG>nvi(1)</STRONG>. He moved
the <EM>standout</EM> attribute to a structure member. The resulting 4.4BSD
<EM>curses</EM> was replaced by <EM>ncurses</EM> over the next ten years.
<STRONG>o</STRONG> UWIN has been defunct since 2012.
<EM>ncurses</EM> 6.0 (2015) added the <EM>A</EM><STRONG>_</STRONG><EM>ITALIC</EM> macro.
</PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
<STRONG><A HREF="ncurses.3x.html">curses(3x)</A></STRONG>, <STRONG><A HREF="curs_addch.3x.html">curs_addch(3x)</A></STRONG>, <STRONG><A HREF="curs_addstr.3x.html">curs_addstr(3x)</A></STRONG>, <STRONG><A HREF="curs_bkgd.3x.html">curs_bkgd(3x)</A></STRONG>,
<STRONG><A HREF="curs_printw.3x.html">curs_printw(3x)</A></STRONG>, <STRONG><A HREF="curs_variables.3x.html">curs_variables(3x)</A></STRONG>
ncurses 6.6 2025-11-11 <STRONG><A HREF="curs_attr.3x.html">curs_attr(3x)</A></STRONG>
</PRE>
<div class="nav">
<ul>
<li><a href="#h2-NAME">NAME</a></li>
<li><a href="#h2-SYNOPSIS">SYNOPSIS</a></li>
<li><a href="#h2-DESCRIPTION">DESCRIPTION</a>
<ul>
<li><a href="#h3-Window-Attributes">Window Attributes</a></li>
<li><a href="#h3-Legacy-Window-Attributes">Legacy Window Attributes</a></li>
<li><a href="#h3-Change-Character-Rendition">Change Character Rendition</a></li>
<li><a href="#h3-Change-Window-Color">Change Window Color</a></li>
<li><a href="#h3-Standout">Standout</a></li>
<li><a href="#h3-Video-Attributes">Video Attributes</a></li>
</ul>
</li>
<li><a href="#h2-RETURN-VALUE">RETURN VALUE</a></li>
<li><a href="#h2-NOTES">NOTES</a></li>
<li><a href="#h2-EXTENSIONS">EXTENSIONS</a></li>
<li><a href="#h2-PORTABILITY">PORTABILITY</a></li>
<li><a href="#h2-HISTORY">HISTORY</a></li>
<li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>
</ul>
</div>
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