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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

       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 at-
       tributes  (such  as  bold,  reverse),  as well as a few bits for color.
       Those bits correspond to the A_COLOR symbol.  The COLOR_PAIR macro pro-
       vides  a value which can be OR'd into the attribute parameter.  For ex-
       ample, 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: 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
              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.


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)