path: root/lib/libcurses/curs_attr.3

'\" t
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.\" $Id: curs_attr.3,v 1.5 2023/10/17 09:52:08 nicm Exp $
.TH curs_attr 3 2023-08-19 "ncurses 6.4" "Library calls"
.ie \n(.g .ds `` \(lq
.el       .ds `` ``
.ie \n(.g .ds '' \(rq
.el       .ds '' ''
.de NS
.ie n  .sp
.el    .sp .5
.ie n  .in +4
.el    .in +2
.nf
.ft CR			\" Courier
..
.de NE
.fi
.ft R
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.el    .in -2
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.de bP
.ie n  .IP \(bu 4
.el    .IP \(bu 2
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.na
.hy 0
.\" ---------------------------------------------------------------------------
.SH NAME
.\" attr_get
\fBattr_get\fP,
\fBwattr_get\fP,
\fBattr_set\fP,
\fBwattr_set\fP,
.\" .br
\fBattr_off\fP,
\fBwattr_off\fP,
\fBattr_on\fP,
\fBwattr_on\fP,
.\" .br
\fBattroff\fP,
\fBwattroff\fP,
\fBattron\fP,
\fBwattron\fP,
\fBattrset\fP,
\fBwattrset\fP,
.\" .br
\fBchgat\fP,
\fBwchgat\fP,
\fBmvchgat\fP,
\fBmvwchgat\fP,
.\" .br
\fBcolor_set\fP,
\fBwcolor_set\fP,
.\" .br
\fBstandend\fP,
\fBwstandend\fP,
\fBstandout\fP,
\fBwstandout\fP \- \fBcurses\fP character and window attribute control routines
.ad
.hy
.\" ---------------------------------------------------------------------------
.SH SYNOPSIS
\fB#include <curses.h>\fP
.sp
\fBint attr_get(attr_t *\fIattrs\fB, short *\fIpair\fB, void *\fIopts\fB);\fR
.br
\fBint wattr_get(WINDOW *\fIwin\fB, attr_t *\fIattrs\fB, short *\fIpair\fB,\fR \fBvoid *\fIopts\fB);\fR
.br
\fBint attr_set(attr_t \fIattrs\fB, short \fIpair\fB, void *\fIopts\fB);\fR
.br
\fBint wattr_set(WINDOW *\fIwin\fB, attr_t \fIattrs\fB, short \fIpair\fB, void *\fIopts\fB);\fR
.sp
\fBint attr_off(attr_t \fIattrs\fB, void *\fIopts\fB);\fR
.br
\fBint wattr_off(WINDOW *\fIwin\fB, attr_t \fIattrs\fB, void *\fIopts\fB);\fR
.br
\fBint attr_on(attr_t \fIattrs\fB, void *\fIopts\fB);\fR
.br
\fBint wattr_on(WINDOW *\fIwin\fB, attr_t \fIattrs\fB, void *\fIopts\fB);\fR
.sp
\fBint attroff(int \fIattrs);\fR
.br
\fBint wattroff(WINDOW *\fIwin\fB, int \fIattrs\fB);\fR
.br
\fBint attron(int \fIattrs\fB);\fR
.br
\fBint wattron(WINDOW *\fIwin\fB, int \fIattrs\fB);\fR
.br
\fBint attrset(int \fIattrs\fB);\fR
.br
\fBint wattrset(WINDOW *\fIwin\fB, int \fIattrs\fB);\fR
.sp
\fBint chgat(int \fIn\fB, attr_t \fIattr\fB, short \fIpair\fB,\fR \fBconst void *\fIopts\fB);\fR
.br
\fBint wchgat(WINDOW *\fIwin\fB,\fR
      \fBint \fIn\fB, attr_t \fIattr\fB,\fR \fBshort \fIpair\fB, const void *\fIopts\fB);\fR
.br
\fBint mvchgat(int \fIy\fB, int \fIx\fB,\fR
      \fBint \fIn\fB, attr_t \fIattr\fB,\fR \fBshort \fIpair\fB, const void *\fIopts\fB);\fR
.br
\fBint mvwchgat(WINDOW *\fIwin, int \fIy, int \fIx\fB,\fR
      \fBint \fIn,\fR \fBattr_t \fIattr\fB, short \fIpair\fB, const void *\fIopts\fB);\fR
.sp
\fBint color_set(short \fIpair\fB, void* \fIopts\fB);\fR
.br
\fBint wcolor_set(WINDOW *\fIwin\fB, short \fIpair\fB,\fR \fBvoid* \fIopts);\fR
.sp
\fBint standend(void);\fP
.br
\fBint wstandend(WINDOW *\fIwin\fB);\fR
.br
\fBint standout(void);\fP
.br
\fBint wstandout(WINDOW *\fIwin\fB);\fR
.\" ---------------------------------------------------------------------------
.SH DESCRIPTION
These routines manipulate the current attributes of the named window,
which then apply to all characters that are written into
the window with \fBwaddch\fP, \fBwaddstr\fP and \fBwprintw\fP.
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.
.PP
These routines do not affect the attributes used
when erasing portions of the window.
See \fBcurs_bkgd\fP(3) for functions which modify the attributes used for
erasing and clearing.
.PP
Routines which do not have a \fBWINDOW*\fP parameter apply to \fBstdscr\fP.
For example,
\fBattr_set\fP is the \fBstdscr\fP variant of \fBwattr_set\fP.
.\" ---------------------------------------------------------------------------
.SS Window attributes
There are two sets of functions:
.bP
functions for manipulating the window attributes and color:
\fBwattr_set\fP and \fBwattr_get\fP.
.bP
functions for manipulating only the window attributes (not color):
\fBwattr_on\fP and \fBwattr_off\fP.
.PP
The \fBwattr_set\fP function sets the current attributes
of the given window to \fIattrs\fP, with color specified by \fIpair\fP.
.PP
Use \fBwattr_get\fP to retrieve attributes for the given window.
.PP
Use \fBattr_on\fP and \fBwattr_on\fP to turn on window attributes, i.e.,
values OR'd together in \fIattr\fP,
without affecting other attributes.
Use \fBattr_off\fP and \fBwattr_off\fP to turn off window attributes,
again values OR'd together in \fIattr\fP,
without affecting other attributes.
.\" ---------------------------------------------------------------------------
.SS Legacy window attributes
The X/Open window attribute routines which \fIset\fP or \fIget\fP,
turn \fIon\fP or \fIoff\fP
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 (\fB_\fP) for the newer names.
.PP
The \fBint\fP datatype used in the legacy routines is treated as if
it is the same size as \fBchtype\fP (used by \fBaddch\fP(3)).
It holds the common video attributes (such as bold, reverse),
as well as a few bits for color.
Those bits correspond to the \fBA_COLOR\fP symbol.
The \fBCOLOR_PAIR\fP macro provides a value which can be OR'd into
the attribute parameter.
For example,
as long as that value fits into the \fBA_COLOR\fP mask,
then these calls produce similar results:
.NS
attrset(A_BOLD | COLOR_PAIR(\fIpair\fP));
attr_set(A_BOLD, \fIpair\fP, NULL);
.NE
.PP
However, if the value does not fit, then the \fBCOLOR_PAIR\fP macro
uses only the bits that fit.
For example, because in ncurses \fBA_COLOR\fP has eight (8) bits,
then \fBCOLOR_PAIR(\fI259\fB)\fR is 4
(i.e., 259 is 4 more than the limit 255).
.PP
The \fBPAIR_NUMBER\fP macro extracts a pair number from an \fBint\fP
(or \fBchtype\fP).
For example, the \fIinput\fP and \fIoutput\fP values in these statements
would be the same:
.NS
int value = A_BOLD | COLOR_PAIR(\fIinput\fP);
int \fIoutput\fP = PAIR_NUMBER(value);
.NE
.PP
The \fBattrset\fP routine is a legacy feature predating SVr4 curses
but kept in X/Open Curses for the same reason that SVr4 curses kept it:
compatibility.
.PP
The remaining \fBattr\fP* functions operate exactly like the corresponding
\fBattr_\fP* functions, except that they take arguments of type \fBint\fP
rather than \fBattr_t\fP.
.PP
There is no corresponding \fBattrget\fP function as such in X/Open Curses,
although ncurses provides \fBgetattrs\fP (see curs_legacy(3)).
.\" ---------------------------------------------------------------------------
.SS Change character rendition
The routine \fBchgat\fP changes the attributes of a given number of characters
starting at the current cursor location of \fBstdscr\fP.
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 \fBwchgat\fP function generalizes this to any window;
the \fBmvwchgat\fP function does a cursor move before acting.
.PP
In these functions,
the color \fIpair\fP argument is a color-pair index
(as in the first argument of \fBinit_pair\fP, see \fBcurs_color\fP(3)).
.\" ---------------------------------------------------------------------------
.SS Change window color
The routine \fBcolor_set\fP sets the current color of the given window to the
foreground/background combination described by the color \fIpair\fP parameter.
.\" ---------------------------------------------------------------------------
.SS Standout
The routine \fBstandout\fP is
the same as \fBattron(A_STANDOUT)\fP.
The routine \fBstandend\fP is the same
as \fBattrset(A_NORMAL)\fP or \fBattrset(0)\fP, that is, it turns off all
attributes.
.PP
X/Open does not mark these \*(``restricted\*('', because
.bP
they have well established legacy use, and
.bP
there is no ambiguity about the way the attributes
might be combined with a color pair.
.\" ---------------------------------------------------------------------------
.SH VIDEO ATTRIBUTES
The following video attributes, defined in \fB<curses.h>\fP, can be passed to
the routines \fBattron\fP, \fBattroff\fP, and \fBattrset\fP, or OR'd with the
characters passed to \fBaddch\fP (see \fBcurs_addch\fP(3)).
.PP
.RS
.TS
l l
_ _ _
l l .
\fBName\fP	\fBDescription\fP
\fBA_NORMAL\fP	Normal display (no highlight)
\fBA_STANDOUT\fP	Best highlighting mode of the terminal.
\fBA_UNDERLINE\fP	Underlining
\fBA_REVERSE\fP	Reverse video
\fBA_BLINK\fP	Blinking
\fBA_DIM\fP	Half bright
\fBA_BOLD\fP	Extra bright or bold
\fBA_PROTECT\fP	Protected mode
\fBA_INVIS\fP	Invisible or blank mode
\fBA_ALTCHARSET\fP	Alternate character set
\fBA_ITALIC\fP	Italics (non-X/Open extension)
\fBA_CHARTEXT\fP	Bit-mask to extract a character
\fBA_COLOR\fP	Bit-mask to extract a color (legacy routines)
.TE
.RE
.PP
These video attributes are supported by \fBattr_on\fP and related functions
(which also support the attributes recognized by \fBattron\fP, etc.):
.PP
.RS
.TS
l l
_ _ _
l l .
\fBName\fP	\fBDescription\fP
\fBWA_HORIZONTAL\fP	Horizontal highlight
\fBWA_LEFT\fP	Left highlight
\fBWA_LOW\fP	Low highlight
\fBWA_RIGHT\fP	Right highlight
\fBWA_TOP\fP	Top highlight
\fBWA_VERTICAL\fP	Vertical highlight
.TE
.RE
.PP
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 \fB1\fP.
.\" ---------------------------------------------------------------------------
.SH NOTES
These functions may be macros:
.sp
.RS
\fBattroff\fP, \fBwattroff\fP, \fBattron\fP, \fBwattron\fP,
\fBattrset\fP, \fBwattrset\fP, \fBstandend\fP and \fBstandout\fP.
.RE
.PP
Color pair values can only be OR'd with attributes if the pair
number is less than 256.
The alternate functions such as \fBcolor_set\fP 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.
.\" ---------------------------------------------------------------------------
.SH HISTORY
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, \fBattrset\fP and \fBattr_set\fP are similar.
SVr4 curses provided the basic features for manipulating video attributes.
However, earlier versions of curses provided a part of these features.
.PP
As seen in 2.8BSD, curses assumed 7-bit characters,
using the eighth bit of a byte to represent the \fIstandout\fP
feature (often implemented as bold and/or reverse video).
The BSD curses library provided functions \fBstandout\fP and \fBstandend\fP
which were carried along into X/Open Curses due to their pervasive use
in legacy applications.
.PP
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 \fBA_\fP symbols for use by applications to manipulate the
other attributes.
There are few useful references for the chronology.
.PP
Goodheart's book
\fIUNIX Curses Explained\fP (1991) describes SVr3 (1987),
commenting on several functions:
.bP
the \fBattron\fP, \fBattroff\fP, \fBattrset\fP functions
(and most of the functions found in SVr4 but not in BSD curses) were
introduced by System V,
.bP
the alternate character set feature with \fBA_ALTCHARSET\fP was
added in SVr2 and improved in SVr3 (by adding \fBacs_map[]\fP),
.bP
\fBstart_color\fP and related color-functions were introduced by System V.3.2,
.bP
pads, soft-keys were added in SVr3, and
.PP
Goodheart did not mention the background character or the \fBcchar_t\fP type.
Those are respectively SVr4 and X/Open features.
He did mention the \fBA_\fP constants, but did not indicate their values.
Those were not the same in different systems,
even for those marked as System V.
.PP
Different Unix systems used different sizes for the bit-fields in \fBchtype\fP
for \fIcharacters\fP and \fIcolors\fP, and took into account the different
integer sizes (32-bit versus 64-bit).
.PP
This table showing the number of bits for \fBA_COLOR\fP
and \fBA_CHARTEXT\fP
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.
.PP
.RS
.TS
l l l l l l
_ _ _ _ _ _
l l l l l l .
\fBYear\fP	\fBSystem\fP	\fBArch\fP	\fBColor\fP	\fBChar\fP	\fBNotes\fP
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 \fBchtype\fP
.TE
.RE
.PP
Notes:
.RS 3
.PP
Regarding HP-UX,
.bP
HP-UX 10.20 (1996) added support for 64-bit PA-RISC processors in 1996.
.bP
HP-UX 10.30 (1997) marked \*(``curses_colr\*('' obsolete.
That version of curses was dropped with HP-UX 11.30 in 2006.
.PP
Regarding OSF/1 (and Tru64),
.bP
These used 64-bit hardware.
Like ncurses, the OSF/1 curses interface is not customized for 32-bit
and 64-bit versions.
.bP
Unlike other systems which evolved from AT&T code,
OSF/1 provided a new implementation for X/Open curses.
.PP
Regarding Solaris,
.bP
The initial release of Solaris was in 1992.
.bP
The \fIxpg4\fP (X/Open) curses was developed by MKS from 1990 to 1995.
Sun's copyright began in 1996.
.bP
Sun updated the X/Open curses interface
after 64-bit support was introduced in 1997,
but did not modify the SVr4 curses interface.
.PP
Regarding U/Win,
.bP
Development of the curses library began in 1991, stopped in 2000.
.bP
Color support was added in 1998.
.bP
The library uses only \fBchtype\fP (no \fBcchar_t\fP).
.RE
.PP
Once X/Open curses was adopted in the mid-1990s, the constraint of
a 32-bit interface with many colors and wide-characters for \fBchtype\fP
became a moot point.
The \fBcchar_t\fP structure (whose size and
members are not specified in X/Open Curses) could be extended as needed.
.PP
Other interfaces are rarely used now:
.bP
BSD curses was improved slightly in 1993/1994 using Keith Bostic's
modification to make the library 8-bit clean for \fBnvi\fP(1).
He moved \fIstandout\fP attribute to a structure member.
.IP
The resulting 4.4BSD curses was replaced by ncurses over the next ten years.
.bP
U/Win is rarely used now.
.\" ---------------------------------------------------------------------------
.SH EXTENSIONS
This implementation provides the \fBA_ITALIC\fP attribute for terminals
which have the \fBenter_italics_mode\fP (\fBsitm\fP)
and \fBexit_italics_mode\fP (\fBritm\fP) capabilities.
Italics are not mentioned in X/Open Curses.
Unlike the other video attributes, \fBA_ITALIC\fP is unrelated
to the \fBset_attributes\fP capabilities.
This implementation makes the assumption that
\fBexit_attribute_mode\fP may also reset italics.
.PP
Each of the functions added by XSI Curses has a parameter \fIopts\fP,
which X/Open Curses still (after more than twenty years) documents
as reserved for future use, saying that it should be \fBNULL\fP.
This implementation uses that parameter in ABI 6 for the functions which
have a color-pair parameter to support \fIextended color pairs\fP:
.bP
For functions which modify the color, e.g.,
\fBwattr_set\fP and \fBwattr_on\fP,
if \fIopts\fP is set it is treated as a pointer to \fBint\fP,
and used to set the color pair instead of the \fBshort\fP \fIpair\fP parameter.
.bP
For functions which retrieve the color, e.g.,
\fBwattr_get\fP,
if \fIopts\fP is set it is treated as a pointer to \fBint\fP,
and used to retrieve the color pair as an \fBint\fP value,
in addition to
retrieving it via the standard pointer to \fBshort\fP parameter.
.bP
For functions which turn attributes off, e.g.,
\fBwattr_off\fP,
the \fIopts\fP parameter is ignored except
except to check that it is \fBNULL\fP.
.\" ---------------------------------------------------------------------------
.SH PORTABILITY
These functions are supported in the XSI Curses standard, Issue 4.
The standard defined the dedicated type for highlights,
\fBattr_t\fP, which was not defined in SVr4 curses.
The functions taking \fBattr_t\fP arguments were not supported under SVr4.
.PP
Very old versions of this library did not force an update of the screen
when changing the attributes.
Use \fBtouchwin\fP to force the screen to match the updated attributes.
.PP
The XSI Curses standard states that whether the traditional functions
\fBattron\fP/\fBattroff\fP/\fBattrset\fP can manipulate attributes other than
\fBA_BLINK\fP, \fBA_BOLD\fP, \fBA_DIM\fP, \fBA_REVERSE\fP, \fBA_STANDOUT\fP, or
\fBA_UNDERLINE\fP is \*(``unspecified\*(''.
Under this implementation as well as
SVr4 curses, these functions correctly manipulate all other highlights
(specifically, \fBA_ALTCHARSET\fP, \fBA_PROTECT\fP, and \fBA_INVIS\fP).
.PP
XSI Curses added these entry points:
.sp
.RS
\fBattr_get\fP, \fBattr_on\fP,
\fBattr_off\fP, \fBattr_set\fP, \fBwattr_on\fP, \fBwattr_off\fP,
\fBwattr_get\fP, \fBwattr_set\fP
.RE
.PP
The new functions are intended to work with
a new series of highlight macros prefixed with \fBWA_\fP.
The older macros have direct counterparts in the newer set of names:
.PP
.RS
.ne 9
.TS
l l
_ _ _
l l .
\fBName\fP	\fBDescription\fP
\fBWA_NORMAL\fP	Normal display (no highlight)
\fBWA_STANDOUT\fP	Best highlighting mode of the terminal.
\fBWA_UNDERLINE\fP	Underlining
\fBWA_REVERSE\fP	Reverse video
\fBWA_BLINK\fP	Blinking
\fBWA_DIM\fP	Half bright
\fBWA_BOLD\fP	Extra bright or bold
\fBWA_ALTCHARSET\fP	Alternate character set
.TE
.RE
.PP
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.:
.bP
The XSI curses standard specifies that each pair of corresponding \fBA_\fP
and \fBWA_\fP-using functions operates on the same current-highlight
information.
.bP
However, in some implementations, those symbols have unrelated values.
.IP
For example, the Solaris \fIxpg4\fP (X/Open) curses declares
\fBattr_t\fP to be an unsigned short integer (16-bits),
while \fBchtype\fP is a unsigned integer (32-bits).
The \fBWA_\fP symbols in this case are different from the \fBA_\fP symbols
because they are used for a smaller datatype which does not
represent \fBA_CHARTEXT\fP or \fBA_COLOR\fP.
.IP
In this implementation (as in many others), the values happen to be
the same because it simplifies copying information between
\fBchtype\fP and \fBcchar_t\fP variables.
.bP
Because ncurses's \fBattr_t\fP can hold a color pair
(in the \fBA_COLOR\fP field),
a call to
\fBwattr_on\fP,
\fBwattr_off\fP, or
\fBwattr_set\fP
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.
.IP
This is consistent with SVr4 curses;
X/Open Curses does not specify this.
.PP
The XSI standard extended conformance level adds new highlights
\fBA_HORIZONTAL\fP, \fBA_LEFT\fP, \fBA_LOW\fP, \fBA_RIGHT\fP, \fBA_TOP\fP,
\fBA_VERTICAL\fP (and corresponding \fBWA_\fP macros for each).
As of August 2013,
no known terminal provides these highlights
(i.e., via the \fBsgr1\fP capability).
.\" ---------------------------------------------------------------------------
.SH RETURN VALUE
All routines return the integer \fBOK\fP on success, or \fBERR\fP on failure.
.PP
X/Open does not define any error conditions.
.PP
This implementation
.bP
returns an error if the window pointer is null.
.bP
returns an error if the color pair parameter
for \fBwcolor_set\fP is outside the range 0..COLOR_PAIRS\-1.
.bP
does not return an error if either of the parameters of \fBwattr_get\fP
used for retrieving attribute or color-pair values is \fBNULL\fP.
.PP
Functions with a \*(``mv\*('' prefix first perform a cursor movement using
\fBwmove\fP, and return an error if the position is outside the window,
or if the window pointer is null.
.\" ---------------------------------------------------------------------------
.SH SEE ALSO
.na
\fBcurses\fP(3),
\fBcurs_addch\fP(3),
\fBcurs_addstr\fP(3),
\fBcurs_bkgd\fP(3),
\fBcurs_printw\fP(3),
\fBcurs_variables\fP(3)