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color(3NCURSES)                                                color(3NCURSES)

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

       # 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);

       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 dis-
       played).  A  programmer  initializes  a  color-pair  with  the  routine
       init_pair.   After  it has been initialized, COLOR_PAIR(n), a macro de-
       fined 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 rou-
       tines has_colors and can_change_color return TRUE or  FALSE,  depending
       on whether the terminal has color capabilities and whether the program-
       mer can change the colors.  The routine color_content allows a program-
       mer  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  manipu-
       lation  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  fore-
       ground color number, and the background color number.  For portable ap-

       -    The value of the  first  argument  must  be  between  1  and  COL-
            OR_PAIRS-1,  except  that  if default colors are used (see use_de-
            fault_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  ac-
            tually  whatever  the terminal implements before color is initial-
            ized.  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 defini-

       As an extension, ncurses allows you to set color pair  0  via  the  as-
       sume_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 rou-
       tine 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-indepen-
       dent 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 com-
       ponents 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 ad-
       dresses pointed to by the second and third arguments are between 0  and

       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.


       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 com-

       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_PAIR-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.

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

                   returns an error If the color table cannot be allocated.

       In the ncurses implementation, there is  a  separate  color  activation
       flag,  color palette, color pairs table, and associated COLORS and COL-
       OR_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 touch-
       es.   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

       -    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.

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

       The  init_pair  routine accepts negative values of foreground and back-
       ground 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 pa-
       rameters when null.

       ncurses(3NCURSES),  initscr(3NCURSES),   attr(3NCURSES),   default_col-


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