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NAME

       start_color, init_pair, init_color, has_colors, can_change_color,
       color_content, pair_content, COLOR_PAIR - curses color manipulation
       routines

SYNOPSIS

       # include <curses.h>

       int start_color(void);
       int init_pair(short pair, short f, short b);
       int init_color(short color, short r, short g, short b);
       bool has_colors(void);
       bool can_change_color(void);
       int color_content(short color, short *r, short *g, short *b);
       int pair_content(short pair, short *f, short *b);

DESCRIPTION

   Overview
       curses  support color attributes on terminals with that capability.  To
       use these routines start_color must  be  called,  usually  right  after
       initscr.  Colors are always used in pairs (referred to as color-pairs).
       A color-pair consists of a foreground  color  (for  characters)  and  a
       background  color  (for  the  blank  field  on which the characters are
       displayed).  A programmer initializes a  color-pair  with  the  routine
       init_pair.   After  it  has  been  initialized,  COLOR_PAIR(n), a macro
       defined in <curses.h>, can be used as a new video attribute.

       If a terminal is capable of redefining colors, the programmer  can  use
       the  routine  init_color  to  change  the  definition  of a color.  The
       routines  has_colors  and  can_change_color  return  TRUE   or   FALSE,
       depending  on  whether  the terminal has color capabilities and whether
       the programmer can change the colors.  The routine color_content allows
       a  programmer to extract the amounts of red, green, and blue components
       in an initialized color.  The routine pair_content allows a  programmer
       to find out how a given color-pair is currently defined.

   Routine Descriptions
       The  start_color  routine  requires no arguments.  It must be called if
       the programmer  wants  to  use  colors,  and  before  any  other  color
       manipulation  routine  is  called.   It  is  good practice to call this
       routine right  after  initscr.   start_color  initializes  eight  basic
       colors (black, red, green, yellow, blue, magenta, cyan, and white), and
       two global variables, COLORS and COLOR_PAIRS (respectively defining the
       maximum number of colors and color-pairs the terminal can support).  It
       also restores the colors on the terminal to the values  they  had  when
       the terminal was just turned on.

       The init_pair routine changes the definition of a color-pair.  It takes
       three arguments: the number  of  the  color-pair  to  be  changed,  the
       foreground color number, and the background color number.  For portable
       applications:

       ·   The  value  of  the  first  argument  must   be   between   1   and
           COLOR_PAIRS-1,   except  that  if  default  colors  are  used  (see
           use_default_colors) the upper limit is adjusted to allow for  extra
           pairs which use a default color in foreground and/or background.

       ·   The  value  of the second and third arguments must be between 0 and
           COLORS.  Color pair 0 is assumed to  be  white  on  black,  but  is
           actually   whatever   the   terminal  implements  before  color  is
           initialized.  It cannot be modified by the application.

       If the color-pair was previously initialized, the screen  is  refreshed
       and  all  occurrences  of  that  color-pair  are  changed  to  the  new
       definition.

       As an extension, ncurses allows  you  to  set  color  pair  0  via  the
       assume_default_colors  routine, or to specify the use of default colors
       (color number -1) if you first invoke the use_default_colors routine.

       The init_color routine changes the definition of  a  color.   It  takes
       four arguments: the number of the color to be changed followed by three
       RGB values (for the amounts of red, green, and blue  components).   The
       value  of  the  first  argument must be between 0 and COLORS.  (See the
       section Colors for the default color index.)  Each of  the  last  three
       arguments must be a value between 0 and 1000.  When init_color is used,
       all occurrences of that color on the screen immediately change  to  the
       new definition.

       The  has_colors  routine requires no arguments.  It returns TRUE if the
       terminal can manipulate colors;  otherwise,  it  returns  FALSE.   This
       routine   facilitates   writing   terminal-independent  programs.   For
       example, a programmer can use it to decide whether to use color or some
       other video attribute.

       The can_change_color routine requires no arguments.  It returns TRUE if
       the terminal supports colors and can change their  definitions;  other,
       it   returns   FALSE.    This  routine  facilitates  writing  terminal-
       independent programs.

       The color_content routine gives programmers a way to find the intensity
       of  the  red, green, and blue (RGB) components in a color.  It requires
       four arguments: the color number, and three  addresses  of  shorts  for
       storing  the  information  about  the  amounts  of red, green, and blue
       components in the given color.  The value of the first argument must be
       between  0  and  COLORS.   The  values that are stored at the addresses
       pointed to by the last three arguments are between 0 (no component) and
       1000 (maximum amount of component).

       The  pair_content  routine allows programmers to find out what colors a
       given color-pair consists of.  It requires three arguments: the  color-
       pair number, and two addresses of shorts for storing the foreground and
       the background color numbers.  The value of the first argument must  be
       between  1  and  COLOR_PAIRS-1.   The  values  that  are  stored at the
       addresses pointed to by the second and third arguments  are  between  0
       and COLORS.

   Colors
       In  <curses.h> the following macros are defined.  These are the default
       colors.  curses also assumes that COLOR_BLACK is the default background
       color for all terminals.

             COLOR_BLACK
             COLOR_RED
             COLOR_GREEN
             COLOR_YELLOW
             COLOR_BLUE
             COLOR_MAGENTA
             COLOR_CYAN
             COLOR_WHITE

RETURN VALUE

       The routines can_change_color() and has_colors() return TRUE or FALSE.

       All  other routines return the integer ERR upon failure and an OK (SVr4
       specifies only "an integer  value  other  than  ERR")  upon  successful
       completion.

       X/Open  defines  no  error conditions.  This implementation will return
       ERR on attempts to use color values outside the  range  0  to  COLORS-1
       (except  for  the default colors extension), or use color pairs outside
       the range 0 to COLOR_PAIRS-1.  Color values used in init_color must  be
       in the range 0 to 1000.  An error is returned from all functions if the
       terminal has not been initialized.  An error is returned from secondary
       functions such as init_pair if start_color was not called.

          init_color
               returns an error if the terminal does not support this feature,
               e.g., if the initialize_color capability  is  absent  from  the
               terminal description.

          start_color
               returns an error if the color table cannot be allocated.

NOTES

       In  the  ncurses  implementation,  there is a separate color activation
       flag, color palette, color  pairs  table,  and  associated  COLORS  and
       COLOR_PAIRS  counts  for  each  screen;  the  start_color function only
       affects the current screen.   The  SVr4/XSI  interface  is  not  really
       designed  with  this  in mind, and historical implementations may use a
       single shared color palette.

       Note that setting an implicit background color via a color pair affects
       only  character  cells  that  a  character  write  operation explicitly
       touches.  To change the background color used when parts  of  a  window
       are blanked by erasing or scrolling operations, see bkgd(3NCURSES).

       Several  caveats  apply  on  386  and  486 machines with VGA-compatible
       graphics:

       ·   COLOR_YELLOW is actually brown.  To get  yellow,  use  COLOR_YELLOW
           combined with the A_BOLD attribute.

       ·   The  A_BLINK  attribute should in theory cause the background to go
           bright.  This often fails to work, and even some cards for which it
           mostly  works  (such  as the Paradise and compatibles) do the wrong
           thing when you try to set a bright "yellow" background (you  get  a
           blinking yellow foreground instead).

       ·   Color RGB values are not settable.

PORTABILITY

       This  implementation satisfies XSI Curses's minimum maximums for COLORS
       and COLOR_PAIRS.

       The  init_pair  routine  accepts  negative  values  of  foreground  and
       background  color to support the use_default_colors extension, but only
       if that routine has been first invoked.

       The assumption that COLOR_BLACK is the default background color for all
       terminals can be modified using the assume_default_colors extension.

       This  implementation checks the pointers, e.g., for the values returned
       by color_content and pair_content, and will  treat  those  as  optional
       parameters when null.

SEE ALSO

       ncurses(3NCURSES),          initscr(3NCURSES),          attr(3NCURSES),
       curses_variables(3NCURSES), default_colors(3NCURSES)

                                                               color(3NCURSES)



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