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curs_attr 3x

curs_attr(3x)                                                    curs_attr(3x)




NAME

       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


SYNOPSIS

       #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);


DESCRIPTION

       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  in-
       sert/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  at-
       tributes 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:

       o   functions for manipulating the window attributes  and  color:  wat-
           tr_set and wattr_get.

       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.

       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  at-
       tr_off  and  wattr_off to turn off window attributes, again values OR'd
       together in attr, without affecting other attributes.


Legacy window attributes

       Most of the window attribute routines are extensions of older  routines
       which  assume  that  color pairs are OR'd into the attribute parameter.
       These older routines use the same name, omitting an underscore (_).

       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: compati-
       bility.

       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 charac-
       ters 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  at-
       tributes  all the way to the end of the current line.  The wchgat func-
       tion generalizes this to any window; the mvwchgat function does a  cur-
       sor 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 parame-
       ter.


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

       o   they have well established legacy use, and

       o   there is no ambiguity about the way the attributes  might  be  com-
           bined with a color pair.


VIDEO ATTRIBUTES

       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

       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.


NOTES

       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.


HISTORY

       X/Open Curses is largely based  on  SVr4  curses,  adding  support  for
       "wide-characters"  (not  specific to Unicode).  Some of the X/Open dif-
       ferences from SVr4 curses address the way video attributes can  be  ap-
       plied  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  at-
       tributes,  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:

       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[]),

       o   start_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  alter-
       nate  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,

          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  in-
              terface is not customized for 32-bit and 64-bit versions.

          o   Unlike other systems which evolved from AT&T code, OSF/1 provid-
              ed 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  inter-
              face.

          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.   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.


EXTENSIONS

       This implementation provides the A_ITALIC attribute for terminals which
       have  the  enter_italics_mode (sitm) and exit_italics_mode (ritm) capa-
       bilities.  Italics are not mentioned in X/Open Curses.  Unlike the oth-
       er  video attributes, A_ITALIC is unrelated to the set_attributes capa-
       bilities.  This  implementation  makes  the  assumption  that  exit_at-
       tribute_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  re-
       served for future use, saying that it should be NULL.  This implementa-
       tion uses that parameter in ABI 6 for the functions which have a color-
       pair parameter to support extended color pairs:

       o   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.

       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 retrieving it via the stan-
           dard 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.


PORTABILITY

       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  cor-
       rectly  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, wat-
              tr_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.:

       o   The XSI curses standard 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 val-
           ues.

           For example, the Solaris xpg4 (X/Open) curses declares attr_t to be
           an unsigned short integer (16-bits), while chtype is a unsigned in-
           teger  (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_HORI-
       ZONTAL, 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).


RETURN VALUE

       All routines return the integer OK on success, or ERR on failure.

       X/Open does not define any error conditions.

       This implementation

       o   returns an error if the window pointer is null.

       o   returns an error if the color pair parameter for wcolor_set is out-
           side 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 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.


SEE ALSO

       curses(3x), curs_addch(3x), curs_addstr(3x), curs_bkgd(3x),
       curs_printw(3x), curs_variables(3x)



                                                                 curs_attr(3x)