MirOS Manual: can_change_color(3), color_content(3), COLOR_PAIR(3), curs_color(3), has_colors(3), init_color(3), init_pair(3), pair_content(3), start_color(3)


curs_color(3)       UNIX Programmer's Manual        curs_color(3)

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 capa-
     bility.   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  at-
     tribute.  If a terminal is capable of redefining colors, the
     programmer can use the routine init_color to change the  de-
     finition   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 program-
     mer 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 glo-
     bal 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

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curs_color(3)       UNIX Programmer's Manual        curs_color(3)

     background color number. For portable applications:

     -    The value of the first argument must be between  1  and
          COLOR_PAIRS-1.

     -    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  facili-
     tates 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 pro-
     grammers a way to find the intensity of the red, green,  and
     blue  (RGB)  components  in a color.  It requires four argu-
     ments: 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  argu-
     ments  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 ad-
     dresses  of  shorts for storing the foreground and the back-
     ground 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  argu-
     ments are between 0 and COLORS.

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curs_color(3)       UNIX Programmer's Manual        curs_color(3)

     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_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  func-
     tions 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 capa-
               bility is absent from the terminal description.

          start_color
               returns an error If the color table cannot be  al-
               located.

NOTES

     In the ncurses implementation, there is a separate color ac-
     tivation flag, color palette, color pairs table, and associ-
     ated 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  back-
     ground  color  used  when  parts  of a window are blanked by
     erasing or scrolling operations, see  curs_bkgd(3).  Several
     caveats  apply  on  386 and 486 machines with VGA-compatible
     graphics:

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curs_color(3)       UNIX Programmer's Manual        curs_color(3)

     -    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  back-
          ground  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 ex-
     tension, 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

     curses(3), curs_initscr(3), curs_attr(3), default_colors(3)

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