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<H1>curs_color 3x</H1>
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<!-- Manpage converted by man2html 3.0.1 -->
<STRONG><A HREF="curs_color.3x.html">curs_color(3x)</A></STRONG>                                           <STRONG><A HREF="curs_color.3x.html">curs_color(3x)</A></STRONG>


</PRE>
<H2>NAME</H2><PRE>
       <STRONG>start_color</STRONG>, <STRONG>init_pair</STRONG>, <STRONG>init_color</STRONG>, <STRONG>has_colors</STRONG>,
       <STRONG>can_change_color</STRONG>, <STRONG>color_content</STRONG>, <STRONG>pair_content</STRONG>, <STRONG>COLOR_PAIR</STRONG>
       - <STRONG>curses</STRONG> color manipulation routines


</PRE>
<H2>SYNOPSIS</H2><PRE>
       <STRONG>#</STRONG> <STRONG>include</STRONG> <STRONG>&lt;curses.h&gt;</STRONG>
       <STRONG>int</STRONG> <STRONG>start_color(void);</STRONG>
       <STRONG>int</STRONG> <STRONG>init_pair(short</STRONG> <STRONG>pair,</STRONG> <STRONG>short</STRONG> <STRONG>f,</STRONG> <STRONG>short</STRONG> <STRONG>b);</STRONG>
       <STRONG>int</STRONG> <STRONG>init_color(short</STRONG> <STRONG>color,</STRONG> <STRONG>short</STRONG> <STRONG>r,</STRONG> <STRONG>short</STRONG> <STRONG>g,</STRONG> <STRONG>short</STRONG> <STRONG>b);</STRONG>
       <STRONG>bool</STRONG> <STRONG>has_colors(void);</STRONG>
       <STRONG>bool</STRONG> <STRONG>can_change_color(void);</STRONG>
       <STRONG>int</STRONG>  <STRONG>color_content(short</STRONG>  <STRONG>color,</STRONG> <STRONG>short</STRONG> <STRONG>*r,</STRONG> <STRONG>short</STRONG> <STRONG>*g,</STRONG> <STRONG>short</STRONG>
       <STRONG>*b);</STRONG>
       <STRONG>int</STRONG> <STRONG>pair_content(short</STRONG> <STRONG>pair,</STRONG> <STRONG>short</STRONG> <STRONG>*f,</STRONG> <STRONG>short</STRONG> <STRONG>*b);</STRONG>


</PRE>
<H2>DESCRIPTION</H2><PRE>
   <STRONG>Overview</STRONG>
       <STRONG>curses</STRONG> support color attributes on terminals with that ca-
       pability.   To  use  these  routines  <STRONG>start_color</STRONG>  must be
       called, usually right after <STRONG>initscr</STRONG>.   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 charac-
       ters are displayed).  A programmer  initializes  a  color-
       pair  with  the routine <STRONG>init_pair</STRONG>.  After it has been ini-
       tialized, <STRONG>COLOR_PAIR</STRONG>(<EM>n</EM>), a macro  defined  in  <STRONG>&lt;curses.h&gt;</STRONG>,
       can be used as a new video attribute.

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

   <STRONG>Routine</STRONG> <STRONG>Descriptions</STRONG>
       The <STRONG>start_color</STRONG> 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 <STRONG>initscr</STRONG>.
       <STRONG>start_color</STRONG> initializes eight basic  colors  (black,  red,
       green,  yellow,  blue,  magenta, cyan, and white), and two
       global variables,  <STRONG>COLORS</STRONG>  and  <STRONG>COLOR_PAIRS</STRONG>  (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 <STRONG>init_pair</STRONG> 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 <STRONG>1</STRONG> and
            <STRONG>COLOR_PAIRS-1</STRONG>.

       -    The value of the second and third arguments  must  be
            between  0 and <STRONG>COLORS</STRONG>.  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  <STRONG>assume_default_colors</STRONG> routine, or to specify the
       use of default colors (color number <STRONG>-1</STRONG>) if you  first  in-
       voke the <STRONG>use_default_colors</STRONG> routine.

       The  <STRONG>init_color</STRONG> 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 <STRONG>0</STRONG> and <STRONG>COLORS</STRONG>.  (See the section
       <STRONG>Colors</STRONG> for the default color index.)   Each  of  the  last
       three  arguments must be a value between 0 and 1000.  When
       <STRONG>init_color</STRONG> is used, all occurrences of that color  on  the
       screen immediately change to the new definition.

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

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

       The <STRONG>color_content</STRONG> 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 <STRONG>short</STRONG>s 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 <STRONG>COLORS</STRONG>.  The values that are stored  at  the
       addresses  pointed  to by the last three arguments are be-
       tween 0 (no component) and 1000 (maximum amount of  compo-
       nent).

       The  <STRONG>pair_content</STRONG>  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 <STRONG>short</STRONG>s for storing the foreground  and  the  background
       color  numbers.   The  value of the first argument must be
       between 1 and <STRONG>COLOR_PAIRS-1</STRONG>.  The values that  are  stored
       at  the addresses pointed to by the second and third argu-
       ments are between 0 and <STRONG>COLORS</STRONG>.

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

             <STRONG>COLOR_BLACK</STRONG>
             <STRONG>COLOR_RED</STRONG>
             <STRONG>COLOR_GREEN</STRONG>
             <STRONG>COLOR_YELLOW</STRONG>
             <STRONG>COLOR_BLUE</STRONG>
             <STRONG>COLOR_MAGENTA</STRONG>
             <STRONG>COLOR_CYAN</STRONG>
             <STRONG>COLOR_WHITE</STRONG>


</PRE>
<H2>RETURN VALUE</H2><PRE>
       The routines <STRONG>can_change_color()</STRONG>  and  <STRONG>has_colors()</STRONG>  return
       <STRONG>TRUE</STRONG> or <STRONG>FALSE</STRONG>.

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

       X/Open  defines  no error conditions.  This implementation
       will return <STRONG>ERR</STRONG> on attempts to use  color  values  outside
       the range 0 to COLORS-1 (except for the default colors ex-
       tension), or use color pairs outside the range 0  to  COL-
       OR_PAIR-1.  Color values used in <STRONG>init_color</STRONG> 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 re-
       turned from  secondary  functions  such  as  <STRONG>init_pair</STRONG>  if
       <STRONG>start_color</STRONG> was not called.

              <STRONG>init_color</STRONG>
                   returns an error if the terminal does not sup-
                   port  this  feature,  e.g.,  if  the  <EM>initial-</EM>
                   <EM>ize</EM><STRONG>_</STRONG><EM>color</EM> capability is absent from the termi-
                   nal description.

              <STRONG>start_color</STRONG>
                   returns an error If the color table cannot  be
                   allocated.


</PRE>
<H2>NOTES</H2><PRE>
       In  the  <EM>ncurses</EM> implementation, there is a separate color
       activation flag, color palette, color pairs table, and as-
       sociated  COLORS  and  COLOR_PAIRS counts for each screen;
       the <STRONG>start_color</STRONG> 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 <STRONG><A HREF="curs_bkgd.3x.html">curs_bkgd(3x)</A></STRONG>.

       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 <STRONG>A_BOLD</STRONG> 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.


</PRE>
<H2>PORTABILITY</H2><PRE>
       This implementation satisfies XSI Curses's  minimum  maxi-
       mums for <STRONG>COLORS</STRONG> and <STRONG>COLOR_PAIRS</STRONG>.

       The  <STRONG>init_pair</STRONG>  routine  accepts  negative values of fore-
       ground  and  background  color  to  support  the   <STRONG>use_de-</STRONG>
       <STRONG>fault_colors</STRONG>  extension, but only if that routine has been
       first invoked.

       The assumption that <STRONG>COLOR_BLACK</STRONG> is the default  background
       color  for  all  terminals  can  be modified using the <STRONG>as-</STRONG>
       <STRONG>sume_default_colors</STRONG> extension.

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


</PRE>
<H2>SEE ALSO</H2><PRE>
       <STRONG><A HREF="ncurses.3x.html">curses(3x)</A></STRONG>, <STRONG><A HREF="curs_initscr.3x.html">curs_initscr(3x)</A></STRONG>, <STRONG><A HREF="curs_attr.3x.html">curs_attr(3x)</A></STRONG>,  <STRONG>default_col-</STRONG>
       <STRONG><A HREF="default_colors.3x.html">ors(3x)</A></STRONG>


                                                         <STRONG><A HREF="curs_color.3x.html">curs_color(3x)</A></STRONG>
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