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<H1 class="no-header">curs_color 3x</H1>
<PRE>
<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><a name="h2-NAME">NAME</a></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><a name="h2-SYNOPSIS">SYNOPSIS</a></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><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>

</PRE>
<H3><a name="h3-Overview">Overview</a></H3><PRE>
       <STRONG>curses</STRONG> supports color attributes on  terminals  with  that
       capability.   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.


</PRE>
<H3><a name="h3-Color-Rendering">Color Rendering</a></H3><PRE>
       The <STRONG>curses</STRONG> library combines these inputs  to  produce  the
       actual  foreground  and  background  colors  shown  on the
       screen:

       <STRONG>o</STRONG>   per-character video attributes (e.g., via <STRONG>waddch</STRONG>),

       <STRONG>o</STRONG>   the window attribute (e.g., by <STRONG>wattrset</STRONG>), and

       <STRONG>o</STRONG>   the background character (e.g., <STRONG>wbkgdset</STRONG>).

       Per-character and window attributes are usually set  by  a
       parameter  containing  video  attributes  including a <STRONG>COL-</STRONG>
       <STRONG>OR_PAIR</STRONG> value.  Some functions such  as  <STRONG>wattr_set</STRONG>  use  a
       separate parameter which is the color pair number.

       The  background character is a special case: it includes a
       character value, just as if it were passed to <STRONG>waddch</STRONG>.

       The <STRONG>curses</STRONG> library does the actual work of combining these
       color pairs in an internal function called from <STRONG>waddch</STRONG>:

       <STRONG>o</STRONG>   If the parameter passed to <STRONG>waddch</STRONG> is <EM>blank</EM>, and it us-
           es the special color pair 0,

           <STRONG>o</STRONG>   <STRONG>curses</STRONG> next checks the window attribute.

           <STRONG>o</STRONG>   If the window attribute does not use color pair 0,
               <STRONG>curses</STRONG>  uses  the  color  pair from the window at-
               tribute.

           <STRONG>o</STRONG>   Otherwise, <STRONG>curses</STRONG> uses the background character.

       <STRONG>o</STRONG>   If the parameter passed to <STRONG>waddch</STRONG> is <EM>not</EM> <EM>blank</EM>, or  it
           does  not use the special color pair 0, <STRONG>curses</STRONG> prefers
           the color pair from the parameter, if it  is  nonzero.
           Otherwise, it tries the window attribute next, and fi-
           nally the background character.

       Some <STRONG>curses</STRONG> functions such as <STRONG>wprintw</STRONG> call <STRONG>waddch</STRONG>.   Those
       do  not  combine  its parameter with a color pair.  Conse-
       quently those calls use only the window attribute  or  the
       background character.


</PRE>
<H3><a name="h3-Routine-Descriptions">Routine Descriptions</a></H3><PRE>
       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> does this:

       <STRONG>o</STRONG>   It  initializes  two global variables, <STRONG>COLORS</STRONG> and <STRONG>COL-</STRONG>
           <STRONG>OR_PAIRS</STRONG> (respectively defining the maximum number  of
           colors and color-pairs the terminal can support).

       <STRONG>o</STRONG>   It initializes the special color pair <STRONG>0</STRONG> to the default
           foreground and  background  colors.   No  other  color
           pairs are initialized.

       <STRONG>o</STRONG>   It  restores  the colors on the terminal to the values
           they had when the terminal was just turned on.

       <STRONG>o</STRONG>   If the terminal supports the <STRONG>initc</STRONG>  (<STRONG>initialize_color</STRONG>)
           capability, <STRONG>start_color</STRONG> initializes its internal table
           representing the red, green and blue components of the
           color palette.

           The components depend on whether the terminal uses CGA
           (aka "ANSI") or HLS (i.e., the <STRONG>hls</STRONG> (<STRONG>hue_lightness_sat-</STRONG>
           <STRONG>uration</STRONG>) capability is set).  The table is initialized
           first for eight basic colors (black, red, green,  yel-
           low,  blue,  magenta, cyan, and white), and after that
           (if the terminal supports more than eight colors)  the
           components are initialized to <STRONG>1000</STRONG>.

           <STRONG>start_color</STRONG>  does  not  attempt  to set the terminal's
           color palette to match its built-in table.  An  appli-
           cation  may use <STRONG>init_color</STRONG> to alter the internal table
           along with the terminal's color.

       These limits apply to color values and color pairs.   Val-
       ues  outside these limits are not legal, and may result in
       a runtime error:

       <STRONG>o</STRONG>   <STRONG>COLORS</STRONG> corresponds to the terminal database's <STRONG>max_col-</STRONG>
           <STRONG>ors</STRONG> capability, which is typically a signed 16-bit in-
           teger (see <STRONG><A HREF="terminfo.5.html">terminfo(5)</A></STRONG>).

       <STRONG>o</STRONG>   color values are expected to be in the range <STRONG>0</STRONG> to <STRONG>COL-</STRONG>
           <STRONG>ORS-1</STRONG>, inclusive (including <STRONG>0</STRONG> and <STRONG>COLORS-1</STRONG>).

       <STRONG>o</STRONG>   a  special  color value <STRONG>-1</STRONG> is used in certain extended
           functions to denote the  <EM>default</EM>  <EM>color</EM>  (see  <STRONG>use_de-</STRONG>
           <STRONG>fault_colors</STRONG>).

       <STRONG>o</STRONG>   <STRONG>COLOR_PAIRS</STRONG>  corresponds  to  the  terminal database's
           <STRONG>max_pairs</STRONG> capability,  which  is  typically  a  signed
           16-bit integer (see <STRONG><A HREF="terminfo.5.html">terminfo(5)</A></STRONG>).

       <STRONG>o</STRONG>   legal  color  pair  values  are in the range <STRONG>1</STRONG> to <STRONG>COL-</STRONG>
           <STRONG>OR_PAIRS-1</STRONG>, inclusive.

       <STRONG>o</STRONG>   color pair <STRONG>0</STRONG> is special; it denotes "no color".

           Color pair <STRONG>0</STRONG> is assumed to be white on black,  but  is
           actually whatever the terminal implements before color
           is initialized.  It cannot be modified by the applica-
           tion.

       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:

       <STRONG>o</STRONG>   The first argument must be a legal color  pair  value.
           If  default  colors  are used (see <STRONG>use_default_colors</STRONG>)
           the upper limit is adjusted to allow for  extra  pairs
           which  use  a default color in foreground and/or back-
           ground.

       <STRONG>o</STRONG>   The second and third arguments  must  be  legal  color
           values.

       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 <STRONG>0</STRONG>
       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 first argument must
       be a legal color value; default  colors  are  not  allowed
       here.   (See  the section <STRONG>Colors</STRONG> for the default color in-
       dex.)  Each of the last three arguments must be a value in
       the  range  <STRONG>0</STRONG>  through <STRONG>1000</STRONG>.  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 first argument must be a legal color
       value,  i.e.,  <STRONG>0</STRONG>  through <STRONG>COLORS-1</STRONG>, inclusive.  The values
       that are stored at the addresses pointed to  by  the  last
       three  arguments are in the range <STRONG>0</STRONG> (no component) through
       <STRONG>1000</STRONG> (maximum amount of component), inclusive.

       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 first argument must be a  legal  color
       value,  i.e., in the range <STRONG>1</STRONG> through <STRONG>COLOR_PAIRS-1</STRONG>, inclu-
       sive.  The values that are stored at the addresses pointed
       to  by  the  second and third arguments are in the range <STRONG>0</STRONG>
       through <STRONG>COLORS</STRONG>, inclusive.


</PRE>
<H3><a name="h3-Colors">Colors</a></H3><PRE>
       In <STRONG>&lt;curses.h&gt;</STRONG> the following macros are defined.  These are
       the  standard colors (ISO-6429).  <STRONG>curses</STRONG> also assumes that
       <STRONG>COLOR_BLACK</STRONG> is the default background color for all termi-
       nals.

             <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><a name="h2-RETURN-VALUE">RETURN VALUE</a></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 <STRONG>0</STRONG> to COLORS-1 (except for the default colors ex-
       tension),  or  use color pairs outside the range <STRONG>0</STRONG> to <STRONG>COL-</STRONG>
       <STRONG>OR_PAIRS-1</STRONG>.  Color values used in <STRONG>init_color</STRONG>  must  be  in
       the  range <STRONG>0</STRONG> to <STRONG>1000</STRONG>.  An error is returned from all func-
       tions if the terminal has not been initialized.  An  error
       is  returned 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  support
               this  feature, e.g., if the <EM>initialize</EM><STRONG>_</STRONG><EM>color</EM> capa-
               bility is absent from the terminal description.

          <STRONG>start_color</STRONG>
               returns an error if the color table cannot be  al-
               located.


</PRE>
<H2><a name="h2-NOTES">NOTES</a></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:

       <STRONG>o</STRONG>   COLOR_YELLOW is actually brown.  To  get  yellow,  use
           COLOR_YELLOW combined with the <STRONG>A_BOLD</STRONG> attribute.

       <STRONG>o</STRONG>   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).

       <STRONG>o</STRONG>   Color RGB values are not settable.


</PRE>
<H2><a name="h2-PORTABILITY">PORTABILITY</a></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><a name="h2-SEE-ALSO">SEE ALSO</a></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>curs_vari-</STRONG>
       <STRONG><A HREF="curs_variables.3x.html">ables(3x)</A></STRONG>, <STRONG><A HREF="default_colors.3x.html">default_colors(3x)</A></STRONG>


                                                         <STRONG><A HREF="curs_color.3x.html">curs_color(3x)</A></STRONG>
</PRE>
<div class="nav">
<ul>
<li><a href="#h2-NAME">NAME</a></li>
<li><a href="#h2-SYNOPSIS">SYNOPSIS</a></li>
<li><a href="#h2-DESCRIPTION">DESCRIPTION</a>
<ul>
<li><a href="#h3-Overview">Overview</a></li>
<li><a href="#h3-Color-Rendering">Color Rendering</a></li>
<li><a href="#h3-Routine-Descriptions">Routine Descriptions</a></li>
<li><a href="#h3-Colors">Colors</a></li>
</ul>
</li>
<li><a href="#h2-RETURN-VALUE">RETURN VALUE</a></li>
<li><a href="#h2-NOTES">NOTES</a></li>
<li><a href="#h2-PORTABILITY">PORTABILITY</a></li>
<li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>
</ul>
</div>
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