Provided by: ncurses-doc_5.9+20140118-1ubuntu1_all bug

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)