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-<H1 class="no-header">curs_color 3x 2023-12-16 ncurses 6.4 Library calls</H1>
+<H1 class="no-header">curs_color 3x 2024-04-20 ncurses 6.4 Library calls</H1>
<PRE>
<STRONG><A HREF="curs_color.3x.html">curs_color(3x)</A></STRONG> Library calls <STRONG><A HREF="curs_color.3x.html">curs_color(3x)</A></STRONG>
</PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
<STRONG>#include</STRONG> <STRONG><curses.h></STRONG>
+ <EM>/*</EM> <EM>variables</EM> <EM>*/</EM>
+ <STRONG>int</STRONG> <STRONG>COLOR_PAIRS;</STRONG>
+ <STRONG>int</STRONG> <STRONG>COLORS;</STRONG>
+
<STRONG>int</STRONG> <STRONG>start_color(void);</STRONG>
<STRONG>bool</STRONG> <STRONG>has_colors(void);</STRONG>
</PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
</PRE><H3><a name="h3-Overview">Overview</a></H3><PRE>
- <EM>curses</EM> 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
- displayed). 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
- 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>color_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.
+ <EM>curses</EM> supports color attributes on terminals with that capability.
+ Call <STRONG>start_color</STRONG> (typically right after <STRONG><A HREF="curs_initscr.3x.html">initscr(3x)</A></STRONG>) to enable this
+ feature. Colors are always used in pairs. A <EM>color</EM> <EM>pair</EM> couples a
+ foreground color for characters with a background color for the blank
+ field on which characters are rendered. <STRONG>init_pair</STRONG> initializes a color
+ pair. The macro <STRONG>COLOR_PAIR</STRONG>(<EM>n</EM>) can then convert the pair to a video
+ attribute.
+
+ If a terminal has the relevant capability, <STRONG>init_color</STRONG> permits
+ (re)definition of a color. <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 capability and
+ whether the programmer can change the colors. <STRONG>color_content</STRONG> permits
+ extraction of the red, green, and blue components of an initialized
+ color. <STRONG>pair_content</STRONG> permits discovery of a color pair's current
+ definition.
-</PRE><H3><a name="h3-
Color-Rendering">Color Rendering</a></H3><PRE>
- The <EM>curses</EM> library combines these inputs to produce the actual
- foreground and background colors shown on the screen:
+</PRE><H3><a name="h3-
Rendering">Rendering</a></H3><PRE>
+ <EM>curses</EM> combines the following data to render a character cell. Any of
+ them can include color information.
- <STRONG>o</STRONG> per-character video attributes (e.g., via <STRONG>waddch</STRONG>),
+ <STRONG>o</STRONG> <EM>curses</EM> character attributes, as from <STRONG><A HREF="curs_addch.3x.html">waddch(3x)</A></STRONG> or <STRONG><A HREF="curs_add_wch.3x.html">wadd_wch(3x)</A></STRONG>
- <STRONG>o</STRONG> the window attribute (e.g., by <STRONG>wattrset</STRONG>), and
+ <STRONG>o</STRONG> window attributes, as from <STRONG><A HREF="curs_attr.3x.html">wattrset(3x)</A></STRONG> or <STRONG><A HREF="curs_attr.3x.html">wattr_set(3x)</A></STRONG>
- <STRONG>o</STRONG> the background character (e.g., <STRONG>wbkgdset</STRONG>).
+ <STRONG>o</STRONG> window background character attributes, as from <STRONG><A HREF="curs_bkgd.3x.html">wbkgdset(3x)</A></STRONG> or
+ <STRONG><A HREF="curs_bkgrnd.3x.html">wbkgrndset(3x)</A></STRONG>
- Per-character and window attributes are usually set by a parameter
- containing video attributes including a color pair value. Some
- functions such as <STRONG>wattr_set</STRONG> use a separate parameter which is the color
- pair number.
+ Per-character and window attributes are usually set through a function
+ parameter containing attributes including a color pair value. Some
+ functions, such as <STRONG>wattr_set</STRONG>, use a separate color pair number
+ parameter.
- The background character is a special case: it includes a character
- value, just as if it were passed to <STRONG>waddch</STRONG>.
+ The background character is a special case: it includes a character
+ code, just as if it were passed to <STRONG>waddch</STRONG>.
- The <EM>curses</EM> library does the actual work of combining these color pairs
+ The <EM>curses</EM> 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
<STRONG>o</STRONG> <EM>curses</EM> next checks the window attribute.
- <STRONG>o</STRONG> If the window attribute does not use color pair 0, <EM>curses</EM> uses
+ <STRONG>o</STRONG> If the window attribute does not use color pair 0, <EM>curses</EM> uses
the color pair from the window attribute.
<STRONG>o</STRONG> Otherwise, <EM>curses</EM> 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, <EM>curses</EM> prefers the color pair from the
- parameter, if it is nonzero. Otherwise, it tries the window
+ <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, <EM>curses</EM> prefers the color pair from the
+ parameter, if it is nonzero. Otherwise, it tries the window
attribute next, and finally the background character.
- Some <EM>curses</EM> functions such as <STRONG>wprintw</STRONG> call <STRONG>waddch</STRONG>. Those do not
- combine its parameter with a color pair. Consequently those calls use
+ Some <EM>curses</EM> functions such as <STRONG>wprintw</STRONG> call <STRONG>waddch</STRONG>. Those do not
+ combine its parameter with a color pair. Consequently those calls use
only the window attribute or the background character.
<STRONG>COLOR_CYAN</STRONG>
<STRONG>COLOR_WHITE</STRONG>
- Some terminals support more than the eight (8) "ANSI" colors. There
+ 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
+ is initialized by <STRONG>start_color</STRONG> to the maximum number of colors the
terminal 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.
+ is initialized by <STRONG>start_color</STRONG> to the maximum number of color pairs the
+ terminal can support. Often, its value is the product <STRONG>COLORS</STRONG> x <STRONG>COLORS</STRONG>,
+ but this is not always true.
+
+ <STRONG>o</STRONG> A few terminals use the HLS color space (see <STRONG>start_color</STRONG> below),
+ ignoring this rule; and
+
+ <STRONG>o</STRONG> terminals supporting a large number of colors are limited to the
+ number of color pairs that a <EM>signed</EM> <EM>short</EM> value can represent.
</PRE><H2><a name="h2-FUNCTIONS">FUNCTIONS</a></H2><PRE>
</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 curses, 4.4BSD curses, or any other previous
- version of curses.
+ 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>
- This implementation satisfies XSI Curses's minimum maximums for <STRONG>COLORS</STRONG>
- and <STRONG>COLOR_PAIRS</STRONG>.
+ 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
+ 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>
+ 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
+ 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
+ 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
+ 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-
+ 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 <STRONG>SCREEN</STRONG> structure) to <STRONG>cur_term</STRONG> (the <STRONG>TERMINAL</STRONG>
+ 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>
+ 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> 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
+ 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>
+ <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
+ 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
+ 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
+ <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="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>
-ncurses 6.4 202
3-12-16 <STRONG><A HREF="curs_color.3x.html">curs_color(3x)</A></STRONG>
+ncurses 6.4 202
4-04-20 <STRONG><A HREF="curs_color.3x.html">curs_color(3x)</A></STRONG>
</PRE>
<div class="nav">
<ul>
<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-Rendering">Rendering</a></li>
</ul>
</li>
<li><a href="#h2-CONSTANTS">CONSTANTS</a></li>
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