+ <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
+ alter the internal table along with the terminal's color.
+
+ These limits apply to color values and color pairs. Values outside
+ these limits are not valid, and may result in a runtime error:
+
+ <STRONG>o</STRONG> <STRONG>COLORS</STRONG> corresponds to the terminal database's <STRONG>max_colors</STRONG>
+ capability, (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>,
+ 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><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>
+ capability, (see <STRONG><A HREF="terminfo.5.html">terminfo(5)</A></STRONG>).
+
+ <STRONG>o</STRONG> valid color pair values are in the range <STRONG>1</STRONG> to <STRONG>COLOR_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 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
+ routine 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-
+ independent 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
+ foreground color number, and the background color number. For portable
+ applications:
+
+ <STRONG>o</STRONG> The first argument must be a valid 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
+ adjusted to allow for extra pairs which use a default color in
+ foreground and/or background.
+
+ <STRONG>o</STRONG> The second and third arguments must be valid 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, <EM>ncurses</EM> allows you to set color pair <STRONG>0</STRONG> via the
+ <STRONG><A HREF="default_colors.3x.html">assume_default_colors(3x)</A></STRONG> routine, or to specify the use of default
+ colors (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
+ extension <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 valid 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
+ modern hardware. The extension <STRONG>init_extended_color</STRONG> uses <STRONG>int</STRONG>s for the
+ color 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
+ components in the given color.
+
+ <STRONG>o</STRONG> The first argument must be a valid 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
+ limits 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 valid 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
+ second and third arguments are in the range <STRONG>0</STRONG> through <STRONG>COLORS</STRONG>,
+ inclusive.
+
+
+</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
+ colors 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 <EM>ncurses</EM> 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-COLOR_PAIR">COLOR_PAIR</a></H3><PRE>
+ <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><H3><a name="h3-PAIR_NUMBER">PAIR_NUMBER</a></H3><PRE>
+ <STRONG>PAIR_NUMBER(</STRONG><EM>attr</EM>) extracts the color information from its <EM>attr</EM>
+ parameter and returns it as a color pair number; it is the inverse
+ operation of <STRONG>COLOR_PAIR</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. SVr4 does document some error
+ conditions 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
+ extension), 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_content</STRONG> if the pair was not initialized using <STRONG>init_pairs</STRONG> and
+ it returns <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 <EM>ncurses</EM> implementation, there is a separate color activation
+ flag, color palette, color pairs table, and associated <STRONG>COLORS</STRONG> and
+ <STRONG>COLOR_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-EXTENSIONS">EXTENSIONS</a></H2><PRE>
+ The functions marked as extensions were designed for <STRONG><A HREF="ncurses.3x.html">ncurses(3x)</A></STRONG>, and
+ are not found in SVr4 <EM>curses</EM>, 4.4BSD <EM>curses</EM>, or any other previous
+ curses implementation.
+
+
+</PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
+ Applications employing <EM>ncurses</EM> extensions should condition their use on
+ the visibility of the <STRONG>NCURSES_VERSION</STRONG> preprocessor macro.
+
+ This implementation satisfies X/Open 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
+ background 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>
+ 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.
+
+ 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 <EM>ncurses</EM>.
+
+
+</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 <EM>SCREEN</EM> structure) to <STRONG>cur_term</STRONG> (the <EM>TERMINAL</EM>
+ structure), 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
+ PCCurses, 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> <EM>ncurses</EM> (1992-present) uses eight bits for <STRONG>A_COLOR</STRONG> in <STRONG>chtype</STRONG>
+ values.
+
+ 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
+ using <STRONG>chtype</STRONG> values.
+
+ <STRONG>o</STRONG> NetBSD curses used 6 bits from 2000 (when colors were first
+ supported) until 2004. At that point, NetBSD changed to use 10
+ bits. As of 2021, that size is unchanged. Like <EM>ncurses</EM> 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-SEE-ALSO">SEE ALSO</a></H2><PRE>
+ <STRONG><A HREF="ncurses.3x.html">curses(3x)</A></STRONG>, <STRONG><A HREF="curs_attr.3x.html">curs_attr(3x)</A></STRONG>, <STRONG><A HREF="curs_initscr.3x.html">curs_initscr(3x)</A></STRONG>, <STRONG><A HREF="curs_variables.3x.html">curs_variables(3x)</A></STRONG>,
+ <STRONG><A HREF="default_colors.3x.html">default_colors(3x)</A></STRONG>