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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>has_colors</STRONG>, <STRONG>can_change_color</STRONG>, <STRONG>init_pair</STRONG>, <STRONG>init_color</STRONG>,
       <STRONG>init_extended_pair</STRONG>, <STRONG>init_extended_color</STRONG>, <STRONG>color_content</STRONG>, <STRONG>pair_content</STRONG>,
       <STRONG>extended_color_content</STRONG>, <STRONG>extended_pair_content</STRONG>, <STRONG>reset_color_pairs</STRONG>,
       <STRONG>COLOR_PAIR</STRONG>, <STRONG>PAIR_NUMBER</STRONG> - <STRONG>curses</STRONG> color manipulation routines


</PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
       <STRONG>#include</STRONG> <STRONG>&lt;curses.h&gt;</STRONG>

       <STRONG>int</STRONG> <STRONG>start_color(void);</STRONG>

       <STRONG>bool</STRONG> <STRONG>has_colors(void);</STRONG>
       <STRONG>bool</STRONG> <STRONG>can_change_color(void);</STRONG>

       <STRONG>int</STRONG> <STRONG>init_pair(short</STRONG> <EM>pair</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <EM>f</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <EM>b</EM><STRONG>);</STRONG>
       <STRONG>int</STRONG> <STRONG>init_color(short</STRONG> <EM>color</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <EM>r</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <EM>g</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <EM>b</EM><STRONG>);</STRONG>
       /* extensions */
       <STRONG>int</STRONG> <STRONG>init_extended_pair(int</STRONG> <EM>pair</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>f</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>b</EM><STRONG>);</STRONG>
       <STRONG>int</STRONG> <STRONG>init_extended_color(int</STRONG> <EM>color</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>r</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>g</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>b</EM><STRONG>);</STRONG>

       <STRONG>int</STRONG> <STRONG>color_content(short</STRONG> <EM>color</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <STRONG>*</STRONG><EM>r</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <STRONG>*</STRONG><EM>g</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <STRONG>*</STRONG><EM>b</EM><STRONG>);</STRONG>
       <STRONG>int</STRONG> <STRONG>pair_content(short</STRONG> <EM>pair</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <STRONG>*</STRONG><EM>f</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <STRONG>*</STRONG><EM>b</EM><STRONG>);</STRONG>
       /* extensions */
       <STRONG>int</STRONG> <STRONG>extended_color_content(int</STRONG> <EM>color</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <STRONG>*</STRONG><EM>r</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <STRONG>*</STRONG><EM>g</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <STRONG>*</STRONG><EM>b</EM><STRONG>);</STRONG>
       <STRONG>int</STRONG> <STRONG>extended_pair_content(int</STRONG> <EM>pair</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <STRONG>*</STRONG><EM>f</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <STRONG>*</STRONG><EM>b</EM><STRONG>);</STRONG>

       /* extensions */
       <STRONG>void</STRONG> <STRONG>reset_color_pairs(void);</STRONG>

       <STRONG>int</STRONG> <STRONG>COLOR_PAIR(int</STRONG> <EM>n</EM><STRONG>);</STRONG>
       <STRONG>PAIR_NUMBER(</STRONG><EM>attrs</EM><STRONG>);</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 characters are  dis-
       played).   A  programmer  initializes  a  color-pair  with  the routine
       <STRONG>init_pair</STRONG>.  After it has been initialized, <STRONG>COLOR_PAIR</STRONG>(<EM>n</EM>) can be used to
       convert the pair to a video attribute.

       If  a  terminal is capable of redefining colors, the programmer can use
       the routine <STRONG>init_color</STRONG> to change the definition of a color.   The  rou-
       tines  <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 program-
       mer can change the colors.  The routine <STRONG>color_content</STRONG> allows a program-
       mer 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  fore-
       ground 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 con-
       taining video attributes including a color pair value.  Some  functions
       such as <STRONG>wattr_set</STRONG> use a separate parameter which is the color pair num-
       ber.

       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 uses 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 attribute.

           <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 attri-
           bute next, and finally the background character.

       Some  <STRONG>curses</STRONG>  functions such as <STRONG>wprintw</STRONG> call <STRONG>waddch</STRONG>.  Those do not com-
       bine its parameter with a color pair.  Consequently those calls use on-
       ly the window attribute or the background character.


</PRE><H2><a name="h2-CONSTANTS">CONSTANTS</a></H2><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 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>

       Some  terminals  support  more than the eight (8) "ANSI" colors.  There
       are no standard names for those additional colors.


</PRE><H2><a name="h2-VARIABLES">VARIABLES</a></H2><PRE>

</PRE><H3><a name="h3-COLORS">COLORS</a></H3><PRE>
       is initialized by <STRONG>start_color</STRONG> to the maximum number of colors the  ter-
       minal can support.


</PRE><H3><a name="h3-COLOR_PAIRS">COLOR_PAIRS</a></H3><PRE>
       is  initialized by <STRONG>start_color</STRONG> to the maximum number of color pairs the
       terminal can support.


</PRE><H2><a name="h2-FUNCTIONS">FUNCTIONS</a></H2><PRE>

</PRE><H3><a name="h3-start_color">start_color</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 manipu-
       lation 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>COLOR_PAIRS</STRONG> (re-
           spectively 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_saturation</STRONG>)  capability  is
           set).   The  table  is  initialized  first  for  eight basic colors
           (black, red, green, yellow, blue, magenta, cyan, and white),  using
           weights that depend upon the CGA/HLS choice.  For "ANSI" colors the
           weights are <STRONG>680</STRONG> or <STRONG>0</STRONG> depending on whether  the  corresponding  red,
           green,  or  blue component is used or not.  That permits using <STRONG>1000</STRONG>
           to represent bold/bright colors.  After the  initial  eight  colors
           (if  the  terminal  supports more than eight colors) the components
           are initialized using the same pattern, but with weights  of  <STRONG>1000</STRONG>.
           SVr4 uses a similar scheme, but uses <STRONG>1000</STRONG> for the components of the
           initial eight colors.

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

       These limits apply to color values and  color  pairs.   Values  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_colors</STRONG> capabili-
           ty, (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>COLORS-1</STRONG>,  inclu-
           sive (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><A HREF="default_colors.3x.html">use_default_colors(3x)</A></STRONG>).

       <STRONG>o</STRONG>   <STRONG>COLOR_PAIRS</STRONG> corresponds to the terminal database's <STRONG>max_pairs</STRONG>  capa-
           bility, (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>COLOR_PAIRS-1</STRONG>, inclu-
           sive.

       <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 what-
           ever  the terminal implements before color is initialized.  It can-
           not be modified by the application.


</PRE><H3><a name="h3-has_colors">has_colors</a></H3><PRE>
       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 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.


</PRE><H3><a name="h3-can_change_color">can_change_color</a></H3><PRE>
       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-indepen-
       dent programs.


</PRE><H3><a name="h3-init_pair">init_pair</a></H3><PRE>
       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  fore-
       ground color number, and the background color number.  For portable ap-
       plications:

       <STRONG>o</STRONG>   The first argument must be a legal color pair  value.   If  default
           colors are used (see <STRONG><A HREF="default_colors.3x.html">use_default_colors(3x)</A></STRONG>) the upper limit is ad-
           justed to allow for extra pairs which use a default color in  fore-
           ground and/or background.

       <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  defini-
       tion.

       As  an  extension,  ncurses  allows you to set color pair <STRONG>0</STRONG> via the <STRONG>as-</STRONG>
       <STRONG><A HREF="assume_default_colors.3x.html">sume_default_colors(3x)</A></STRONG> routine, or to specify the use of default  col-
       ors  (color  number  <STRONG>-1</STRONG>) if you first invoke the <STRONG><A HREF="default_colors.3x.html">use_default_colors(3x)</A></STRONG>
       routine.


</PRE><H3><a name="h3-init_extended_pair">init_extended_pair</a></H3><PRE>
       Because <STRONG>init_pair</STRONG> uses signed <STRONG>short</STRONG>s for its  parameters,  that  limits
       color-pairs  and  color-values to 32767 on modern hardware.  The exten-
       sion <STRONG>init_extended_pair</STRONG> uses <STRONG>int</STRONG>s for the color-pair  and  color-value,
       allowing a larger number of colors to be supported.


</PRE><H3><a name="h3-init_color">init_color</a></H3><PRE>
       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).

       <STRONG>o</STRONG>   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
           index.)

       <STRONG>o</STRONG>   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.


</PRE><H3><a name="h3-init_extended_color">init_extended_color</a></H3><PRE>
       Because  <STRONG>init_color</STRONG>  uses signed <STRONG>short</STRONG>s for its parameters, that limits
       color-values and their red, green, and blue components to 32767 on mod-
       ern hardware.  The extension <STRONG>init_extended_color</STRONG> uses <STRONG>int</STRONG>s for the col-
       or value and for setting the red, green, and blue components,  allowing
       a larger number of colors to be supported.


</PRE><H3><a name="h3-color_content">color_content</a></H3><PRE>
       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  com-
       ponents in the given color.

       <STRONG>o</STRONG>   The  first  argument  must  be a legal color value, i.e., <STRONG>0</STRONG> through
           <STRONG>COLORS-1</STRONG>, inclusive.

       <STRONG>o</STRONG>   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.


</PRE><H3><a name="h3-extended_color_content">extended_color_content</a></H3><PRE>
       Because <STRONG>color_content</STRONG> uses signed <STRONG>short</STRONG>s for its parameters, that  lim-
       its  color-values and their red, green, and blue components to 32767 on
       modern hardware.  The extension <STRONG>extended_color_content</STRONG>  uses  <STRONG>int</STRONG>s  for
       the  color value and for returning the red, green, and blue components,
       allowing a larger number of colors to be supported.


</PRE><H3><a name="h3-pair_content">pair_content</a></H3><PRE>
       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.

       <STRONG>o</STRONG>   The  first argument must be a legal color value, i.e., in the range
           <STRONG>1</STRONG> through <STRONG>COLOR_PAIRS-1</STRONG>, inclusive.

       <STRONG>o</STRONG>   The values that are stored at the addresses pointed to by the  sec-
           ond  and  third arguments are in the range <STRONG>0</STRONG> through <STRONG>COLORS</STRONG>, inclu-
           sive.


</PRE><H3><a name="h3-extended_pair_content">extended_pair_content</a></H3><PRE>
       Because <STRONG>pair_content</STRONG> uses signed <STRONG>short</STRONG>s for its parameters, that limits
       color-pair and color-values to 32767 on modern hardware.  The extension
       <STRONG>extended_pair_content</STRONG> uses <STRONG>int</STRONG>s for the color pair  and  for  returning
       the  foreground and background colors, allowing a larger number of col-
       ors to be supported.


</PRE><H3><a name="h3-reset_color_pairs">reset_color_pairs</a></H3><PRE>
       The extension <STRONG>reset_color_pairs</STRONG> tells ncurses to  discard  all  of  the
       color-pair  information  which was set with <STRONG>init_pair</STRONG>.  It also touches
       the current- and standard-screens, allowing an  application  to  switch
       color palettes rapidly.


</PRE><H3><a name="h3-PAIR_NUMBER">PAIR_NUMBER</a></H3><PRE>
       <STRONG>PAIR_NUMBER(</STRONG><EM>attrs</EM>)  extracts  the  color value from its <EM>attrs</EM> parameter
       and returns it as a color pair number.


</PRE><H3><a name="h3-COLOR_PAIR">COLOR_PAIR</a></H3><PRE>
       Its inverse <STRONG>COLOR_PAIR(</STRONG><EM>n</EM><STRONG>)</STRONG> converts a color pair number to an attribute.
       Attributes  can  hold color pairs in the range 0 to 255.  If you need a
       color pair larger than that, you must use functions  such  as  <STRONG>attr_set</STRONG>
       (which  pass  the  color  pair as a separate parameter) rather than the
       legacy functions such as <STRONG>attrset</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 com-
       pletion.

       X/Open defines no error conditions.  SVr4 does document some error con-
       ditions which apply in general:

       <STRONG>o</STRONG>   This implementation will return <STRONG>ERR</STRONG> on attempts to use color values
           outside the range <STRONG>0</STRONG> to <STRONG>COLORS</STRONG>-1 (except for the default colors  ex-
           tension), or use color pairs outside the range <STRONG>0</STRONG> to <STRONG>COLOR_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 functions 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>o</STRONG>   SVr4  does much the same, except that it returns <STRONG>ERR</STRONG> from <STRONG>pair_con-</STRONG>
           <STRONG>tent</STRONG> if the pair was not initialized using <STRONG>init_pairs</STRONG>  and  it  re-
           turns  <STRONG>ERR</STRONG>  from  <STRONG>color_content</STRONG>  if  the  terminal does not support
           changing colors.

           This implementation does not return <STRONG>ERR</STRONG> for either case.

       Specific functions make additional checks:

          <STRONG>init_color</STRONG>
               returns an error if the terminal does not support this feature,
               e.g.,  if  the  <STRONG>initialize_color</STRONG>  capability is absent from the
               terminal description.

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


</PRE><H2><a name="h2-NOTES">NOTES</a></H2><PRE>
       In the <STRONG>ncurses</STRONG> implementation, there is  a  separate  color  activation
       flag,  color palette, color pairs table, and associated <STRONG>COLORS</STRONG> and <STRONG>COL-</STRONG>
       <STRONG>OR_PAIRS</STRONG> 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.

       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 older x86 machines  (e.g.,  i386,  i486)  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 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).

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


</PRE><H2><a name="h2-HISTORY">HISTORY</a></H2><PRE>
       SVr3.2 introduced color support to curses in 1987.

       SVr4 made internal changes, e.g., moving  the  storage  for  the  color
       state  from  <STRONG>SP</STRONG> (the <STRONG>SCREEN</STRONG> structure) to <STRONG>cur_term</STRONG> (the <STRONG>TERMINAL</STRONG> struc-
       ture), but provided the same set of library functions.

       SVr4 curses limits the number of color pairs  to  64,  reserving  color
       pair  zero  (0)  as the terminal's initial uncolored state.  This limit
       arises because the color pair information is a bitfield in  the  <STRONG>chtype</STRONG>
       data type (denoted by <STRONG>A_COLOR</STRONG>).

       Other implementations of curses had different limits:

       <STRONG>o</STRONG>   PCCurses (1987-1990) provided for only eight (8) colors.

       <STRONG>o</STRONG>   PDCurses  (1992-present)  inherited the 8-color limitation from PC-
           Curses, but changed this to 256 in version 2.5 (2001),  along  with
           changing <STRONG>chtype</STRONG> from 16-bits to 32-bits.

       <STRONG>o</STRONG>   X/Open Curses (1992-present) added a new structure <STRONG>cchar_t</STRONG> to store
           the character, attributes and color-pair values, allowing increased
           range  of  color-pairs.   Both  color-pairs and color-values used a
           signed <STRONG>short</STRONG>, limiting values to 15 bits.

       <STRONG>o</STRONG>   ncurses (1992-present) uses eight bits for <STRONG>A_COLOR</STRONG> in  <STRONG>chtype</STRONG>  val-
           ues.

           Version  5.3  provided  a wide-character interface (2002), but left
           color-pairs as part of the attributes-field.

           Since version 6 (2015), ncurses uses a separate <STRONG>int</STRONG> for color-pairs
           in the <STRONG>cchar_t</STRONG> values.  When those color-pair values fit in 8 bits,
           ncurses allows color-pairs to be manipulated via the functions  us-
           ing <STRONG>chtype</STRONG> values.

       <STRONG>o</STRONG>   NetBSD  curses  used  6 bits from 2000 (when colors were first sup-
           ported) until 2004.  At that point, NetBSD changed to use 10  bits.
           As of 2021, that size is unchanged.  Like ncurses before version 6,
           the NetBSD color-pair information is stored in the attributes field
           of  <STRONG>cchar_t</STRONG>,  limiting the number of color-pairs by the size of the
           bitfield.


</PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
       This implementation satisfies XSI Curses's minimum maximums for  <STRONG>COLORS</STRONG>
       and <STRONG>COLOR_PAIRS</STRONG>.

       The  <STRONG>init_pair</STRONG>  routine accepts negative values of foreground and back-
       ground color to support the <STRONG><A HREF="default_colors.3x.html">use_default_colors(3x)</A></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><A HREF="default_colors.3x.html">assume_default_colors(3x)</A></STRONG>  exten-
       sion.

       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 pa-
       rameters when null.

       X/Open  Curses  does  not  specify a limit for the number of colors and
       color pairs which a terminal can support.  However, in its use of <STRONG>short</STRONG>
       for  the  parameters,  it carries over SVr4's implementation detail for
       the compiled terminfo database, which uses signed 16-bit numbers.  This
       implementation  provides extended versions of those functions which use
       <STRONG>short</STRONG> parameters, allowing applications to use larger color- and  pair-
       numbers.

       The <STRONG>reset_color_pairs</STRONG> function is an extension of ncurses.


</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><A HREF="curs_variables.3x.html">curs_variables(3x)</A></STRONG>, <STRONG>de-</STRONG>
       <STRONG><A HREF="default_colors.3x.html">fault_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>
</ul>
</li>
<li><a href="#h2-CONSTANTS">CONSTANTS</a></li>
<li><a href="#h2-VARIABLES">VARIABLES</a>
<ul>
<li><a href="#h3-COLORS">COLORS</a></li>
<li><a href="#h3-COLOR_PAIRS">COLOR_PAIRS</a></li>
</ul>
</li>
<li><a href="#h2-FUNCTIONS">FUNCTIONS</a>
<ul>
<li><a href="#h3-start_color">start_color</a></li>
<li><a href="#h3-has_colors">has_colors</a></li>
<li><a href="#h3-can_change_color">can_change_color</a></li>
<li><a href="#h3-init_pair">init_pair</a></li>
<li><a href="#h3-init_extended_pair">init_extended_pair</a></li>
<li><a href="#h3-init_color">init_color</a></li>
<li><a href="#h3-init_extended_color">init_extended_color</a></li>
<li><a href="#h3-color_content">color_content</a></li>
<li><a href="#h3-extended_color_content">extended_color_content</a></li>
<li><a href="#h3-pair_content">pair_content</a></li>
<li><a href="#h3-extended_pair_content">extended_pair_content</a></li>
<li><a href="#h3-reset_color_pairs">reset_color_pairs</a></li>
<li><a href="#h3-PAIR_NUMBER">PAIR_NUMBER</a></li>
<li><a href="#h3-COLOR_PAIR">COLOR_PAIR</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-HISTORY">HISTORY</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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