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* @Id: curs_color.3x,v 1.19 2002/02/16 22:38:32 tom Exp @
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<H1>curs_color 3x</H1>
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<PRE>
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</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
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><curses.h></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>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.
<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 applications:
- 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> (the 0 color pair is wired to
white on black and cannot be changed).
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_colors</STRONG> routine, or to specify the
use of default colors (color 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
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.
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 value of the first argument must be
between 0 and <STRONG>COLORS</STRONG>. The values that are stored at the
addresses pointed to by the last three arguments are
between 0 (no component) and 1000 (maximum amount of com-
ponent).
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 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 argu-
ments 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.
</PRE>
<H2>NOTES</H2><PRE>
In the <EM>ncurses</EM> implementation, there is a separate color
activation flag, color palette, color pairs table, and
associated 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:
- 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_default_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>assume_default_colors</STRONG> extension,
</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>
</PRE>
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