1curs_color(3X) curs_color(3X)
2
6 start_color, init_pair, init_color, has_colors, can_change_color,
7 color_content, pair_content, COLOR_PAIR - curses color manipulation
8 routines
9
11 # include <curses.h>
12 int start_color(void);
14 int init_pair(short pair, short f, short b);
15 int init_color(short color, short r, short g, short b);
16 bool has_colors(void);
17 bool can_change_color(void);
18 int color_content(short color, short *r, short *g, short *b);
19 int pair_content(short pair, short *f, short *b);
20
22 Overview
23 curses support color attributes on terminals with that capability. To
24 use these routines start_color must be called, usually right after
25 initscr. Colors are always used in pairs (referred to as color-pairs).
26 A color-pair consists of a foreground color (for characters) and a
27 background color (for the blank field on which the characters are dis‐
28 played). A programmer initializes a color-pair with the routine
29 init_pair. After it has been initialized, COLOR_PAIR(n), a macro de‐
30 fined in <curses.h>, can be used as a new video attribute.
31 If a terminal is capable of redefining colors, the programmer can use
33 the routine init_color to change the definition of a color. The rou‐
34 tines has_colors and can_change_color return TRUE or FALSE, depending
35 on whether the terminal has color capabilities and whether the program‐
36 mer can change the colors. The routine color_content allows a program‐
37 mer to extract the amounts of red, green, and blue components in an
38 initialized color. The routine pair_content allows a programmer to
39 find out how a given color-pair is currently defined.
40 Routine Descriptions
42 The start_color routine requires no arguments. It must be called if
43 the programmer wants to use colors, and before any other color manipu‐
44 lation routine is called. It is good practice to call this routine
45 right after initscr. start_color initializes eight basic colors
46 (black, red, green, yellow, blue, magenta, cyan, and white), and two
47 global variables, COLORS and COLOR_PAIRS (respectively defining the
48 maximum number of colors and color-pairs the terminal can support). It
49 also restores the colors on the terminal to the values they had when
50 the terminal was just turned on.
51 The init_pair routine changes the definition of a color-pair. It takes
53 three arguments: the number of the color-pair to be changed, the fore‐
54 ground color number, and the background color number. For portable ap‐
55 plications:
56 · The value of the first argument must be between 1 and COL‐
58 OR_PAIRS-1, except that if default colors are used (see use_de‐
59 fault_colors) the upper limit is adjusted to allow for extra pairs
60 which use a default color in foreground and/or background.
61 · The value of the second and third arguments must be between 0 and
63 COLORS. Color pair 0 is assumed to be white on black, but is actu‐
64 ally whatever the terminal implements before color is initialized.
65 It cannot be modified by the application.
66 If the color-pair was previously initialized, the screen is refreshed
68 and all occurrences of that color-pair are changed to the new defini‐
69 tion.
70 As an extension, ncurses allows you to set color pair 0 via the as‐
72 sume_default_colors routine, or to specify the use of default colors
73 (color number -1) if you first invoke the use_default_colors routine.
74 The init_color routine changes the definition of a color. It takes
76 four arguments: the number of the color to be changed followed by three
77 RGB values (for the amounts of red, green, and blue components). The
78 value of the first argument must be between 0 and COLORS. (See the
79 section Colors for the default color index.) Each of the last three
80 arguments must be a value between 0 and 1000. When init_color is used,
81 all occurrences of that color on the screen immediately change to the
82 new definition.
83 The has_colors routine requires no arguments. It returns TRUE if the
85 terminal can manipulate colors; otherwise, it returns FALSE. This rou‐
86 tine facilitates writing terminal-independent programs. For example, a
87 programmer can use it to decide whether to use color or some other
88 video attribute.
89 The can_change_color routine requires no arguments. It returns TRUE if
91 the terminal supports colors and can change their definitions; other,
92 it returns FALSE. This routine facilitates writing terminal-indepen‐
93 dent programs.
94 The color_content routine gives programmers a way to find the intensity
96 of the red, green, and blue (RGB) components in a color. It requires
97 four arguments: the color number, and three addresses of shorts for
98 storing the information about the amounts of red, green, and blue com‐
99 ponents in the given color. The value of the first argument must be
100 between 0 and COLORS. The values that are stored at the addresses
101 pointed to by the last three arguments are between 0 (no component) and
102 1000 (maximum amount of component).
103 The pair_content routine allows programmers to find out what colors a
105 given color-pair consists of. It requires three arguments: the color-
106 pair number, and two addresses of shorts for storing the foreground and
107 the background color numbers. The value of the first argument must be
108 between 1 and COLOR_PAIRS-1. The values that are stored at the ad‐
109 dresses pointed to by the second and third arguments are between 0 and
110 COLORS.
111 Colors
113 In <curses.h> the following macros are defined. These are the default
114 colors. curses also assumes that COLOR_BLACK is the default background
115 color for all terminals.
116 COLOR_BLACK
118 COLOR_RED
119 COLOR_GREEN
120 COLOR_YELLOW
121 COLOR_BLUE
122 COLOR_MAGENTA
123 COLOR_CYAN
124 COLOR_WHITE
125
127 The routines can_change_color() and has_colors() return TRUE or FALSE.
128 All other routines return the integer ERR upon failure and an OK (SVr4
130 specifies only "an integer value other than ERR") upon successful com‐
131 pletion.
132 X/Open defines no error conditions. This implementation will return
134 ERR on attempts to use color values outside the range 0 to COLORS-1
135 (except for the default colors extension), or use color pairs outside
136 the range 0 to COLOR_PAIRS-1. Color values used in init_color must be
137 in the range 0 to 1000. An error is returned from all functions if the
138 terminal has not been initialized. An error is returned from secondary
139 functions such as init_pair if start_color was not called.
140 init_color
142 returns an error if the terminal does not support this feature,
143 e.g., if the initialize_color capability is absent from the
144 terminal description.
145 start_color
147 returns an error if the color table cannot be allocated.
148
150 In the ncurses implementation, there is a separate color activation
151 flag, color palette, color pairs table, and associated COLORS and COL‐
152 OR_PAIRS counts for each screen; the start_color function only affects
153 the current screen. The SVr4/XSI interface is not really designed with
154 this in mind, and historical implementations may use a single shared
155 color palette.
156 Note that setting an implicit background color via a color pair affects
158 only character cells that a character write operation explicitly touch‐
159 es. To change the background color used when parts of a window are
160 blanked by erasing or scrolling operations, see curs_bkgd(3X).
161 Several caveats apply on 386 and 486 machines with VGA-compatible
163 graphics:
164 · COLOR_YELLOW is actually brown. To get yellow, use COLOR_YELLOW
166 combined with the A_BOLD attribute.
167 · The A_BLINK attribute should in theory cause the background to go
169 bright. This often fails to work, and even some cards for which it
170 mostly works (such as the Paradise and compatibles) do the wrong
171 thing when you try to set a bright "yellow" background (you get a
172 blinking yellow foreground instead).
173 · Color RGB values are not settable.
175
177 This implementation satisfies XSI Curses's minimum maximums for COLORS
178 and COLOR_PAIRS.
179 The init_pair routine accepts negative values of foreground and back‐
181 ground color to support the use_default_colors extension, but only if
182 that routine has been first invoked.
183 The assumption that COLOR_BLACK is the default background color for all
185 terminals can be modified using the assume_default_colors extension.
186 This implementation checks the pointers, e.g., for the values returned
188 by color_content and pair_content, and will treat those as optional pa‐
189 rameters when null.
190
192 curses(3X), curs_initscr(3X), curs_attr(3X), curs_variables(3X), de‐
193 fault_colors(3X)
194 curs_color(3X)