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* @Id: curs_color.3x,v 1.27 2005/05/15 16:55:36 tom Exp @
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<H1>curs_color 3x</H1>
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<PRE>
<!-- 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><curses.h></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><curses.h></STRONG>,
can be used as a new 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 ca-
pabilities and whether the programmer can change the col-
ors. The routine <STRONG>color_content</STRONG> allows a programmer to ex-
tract the amounts of red, green, and blue components in an
initialized color. The routine <STRONG>pair_content</STRONG> allows a pro-
grammer 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 applica-
tions:
- 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_col-</STRONG>
<STRONG>ors</STRONG> routine, or to specify the use of default colors (col-
or number <STRONG>-1</STRONG>) if you first invoke 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 re-
turns <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 argu-
ments. 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 pro-
grams. 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 ar-
gument must be between 0 and <STRONG>COLORS</STRONG>. The values that are
stored at the addresses pointed to by the last three argu-
ments are between 0 (no component) and 1000 (maximum
amount of component). 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 fore-
ground 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 arguments are between 0 and <STRONG>COLORS</STRONG>.
<STRONG>Colors</STRONG>
In <STRONG><curses.h></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 back-
ground 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 ma-
chines 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>
</PRE>
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