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);
13 int init_pair(short pair, short f, short b);
14 int init_color(short color, short r, short g, short b);
15 bool has_colors(void);
16 bool can_change_color(void);
17 int color_content(short color, short *r, short *g, short *b);
18 int pair_content(short pair, short *f, short *b);
19
21 Overview
22 curses support color attributes on terminals with that capability. To
23 use these routines start_color must be called, usually right after
24 initscr. Colors are always used in pairs (referred to as color-pairs).
25 A color-pair consists of a foreground color (for characters) and a
26 background color (for the blank field on which the characters are dis‐
27 played). A programmer initializes a color-pair with the routine
28 init_pair. After it has been initialized, COLOR_PAIR(n), a macro de‐
29 fined in <curses.h>, can be used as a new video attribute.
30 If a terminal is capable of redefining colors, the programmer can use
32 the routine init_color to change the definition of a color. The rou‐
33 tines has_colors and can_change_color return TRUE or FALSE, depending
34 on whether the terminal has color capabilities and whether the program‐
35 mer can change the colors. The routine color_content allows a program‐
36 mer to extract the amounts of red, green, and blue components in an
37 initialized color. The routine pair_content allows a programmer to
38 find out how a given color-pair is currently defined.
39 Routine Descriptions
41 The start_color routine requires no arguments. It must be called if
42 the programmer wants to use colors, and before any other color manipu‐
43 lation routine is called. It is good practice to call this routine
44 right after initscr. start_color initializes eight basic colors
45 (black, red, green, yellow, blue, magenta, cyan, and white), and two
46 global variables, COLORS and COLOR_PAIRS (respectively defining the
47 maximum number of colors and color-pairs the terminal can support). It
48 also restores the colors on the terminal to the values they had when
49 the terminal was just turned on.
50 The init_pair routine changes the definition of a color-pair. It takes
52 three arguments: the number of the color-pair to be changed, the fore‐
53 ground color number, and the background color number. For portable ap‐
54 plications:
55 - The value of the first argument must be between 1 and COL‐
57 OR_PAIRS-1.
58 - The value of the second and third arguments must be between 0 and
60 COLORS. Color pair 0 is assumed to be white on black, but is ac‐
61 tually whatever the terminal implements before color is initial‐
62 ized. It cannot be modified by the application.
63 If the color-pair was previously initialized, the screen is refreshed
65 and all occurrences of that color-pair are changed to the new defini‐
66 tion.
67 As an extension, ncurses allows you to set color pair 0 via the as‐
69 sume_default_colors routine, or to specify the use of default colors
70 (color number -1) if you first invoke the use_default_colors routine.
71 The init_color routine changes the definition of a color. It takes
73 four arguments: the number of the color to be changed followed by three
74 RGB values (for the amounts of red, green, and blue components). The
75 value of the first argument must be between 0 and COLORS. (See the
76 section Colors for the default color index.) Each of the last three
77 arguments must be a value between 0 and 1000. When init_color is used,
78 all occurrences of that color on the screen immediately change to the
79 new definition.
80 The has_colors routine requires no arguments. It returns TRUE if the
82 terminal can manipulate colors; otherwise, it returns FALSE. This rou‐
83 tine facilitates writing terminal-independent programs. For example, a
84 programmer can use it to decide whether to use color or some other
85 video attribute.
86 The can_change_color routine requires no arguments. It returns TRUE if
88 the terminal supports colors and can change their definitions; other,
89 it returns FALSE. This routine facilitates writing terminal-indepen‐
90 dent programs.
91 The color_content routine gives programmers a way to find the intensity
93 of the red, green, and blue (RGB) components in a color. It requires
94 four arguments: the color number, and three addresses of shorts for
95 storing the information about the amounts of red, green, and blue com‐
96 ponents in the given color. The value of the first argument must be
97 between 0 and COLORS. The values that are stored at the addresses
98 pointed to by the last three arguments are between 0 (no component) and
99 1000 (maximum amount of component).
100 The pair_content routine allows programmers to find out what colors a
102 given color-pair consists of. It requires three arguments: the color-
103 pair number, and two addresses of shorts for storing the foreground and
104 the background color numbers. The value of the first argument must be
105 between 1 and COLOR_PAIRS-1. The values that are stored at the ad‐
106 dresses pointed to by the second and third arguments are between 0 and
107 COLORS.
108 Colors
110 In <curses.h> the following macros are defined. These are the default
111 colors. curses also assumes that COLOR_BLACK is the default background
112 color for all terminals.
113 COLOR_BLACK
115 COLOR_RED
116 COLOR_GREEN
117 COLOR_YELLOW
118 COLOR_BLUE
119 COLOR_MAGENTA
120 COLOR_CYAN
121 COLOR_WHITE
122
124 The routines can_change_color() and has_colors() return TRUE or FALSE.
125 All other routines return the integer ERR upon failure and an OK (SVr4
127 specifies only "an integer value other than ERR") upon successful com‐
128 pletion.
129 X/Open defines no error conditions. This implementation will return
131 ERR on attempts to use color values outside the range 0 to COLORS-1
132 (except for the default colors extension), or use color pairs outside
133 the range 0 to COLOR_PAIR-1. Color values used in init_color must be
134 in the range 0 to 1000. An error is returned from all functions if the
135 terminal has not been initialized. An error is returned from secondary
136 functions such as init_pair if start_color was not called.
137 init_color
139 returns an error if the terminal does not support this fea‐
140 ture, e.g., if the initialize_color capability is absent
141 from the terminal description.
142 start_color
144 returns an error If the color table cannot be allocated.
145
147 In the ncurses implementation, there is a separate color activation
148 flag, color palette, color pairs table, and associated COLORS and COL‐
149 OR_PAIRS counts for each screen; the start_color function only affects
150 the current screen. The SVr4/XSI interface is not really designed with
151 this in mind, and historical implementations may use a single shared
152 color palette.
153 Note that setting an implicit background color via a color pair affects
155 only character cells that a character write operation explicitly touch‐
156 es. To change the background color used when parts of a window are
157 blanked by erasing or scrolling operations, see curs_bkgd(3X).
158 Several caveats apply on 386 and 486 machines with VGA-compatible
160 graphics:
161 - COLOR_YELLOW is actually brown. To get yellow, use COLOR_YELLOW
163 combined with the A_BOLD attribute.
164 - The A_BLINK attribute should in theory cause the background to go
166 bright. This often fails to work, and even some cards for which
167 it mostly works (such as the Paradise and compatibles) do the
168 wrong thing when you try to set a bright "yellow" background (you
169 get a blinking yellow foreground instead).
170 - Color RGB values are not settable.
172
174 This implementation satisfies XSI Curses's minimum maximums for COLORS
175 and COLOR_PAIRS.
176 The init_pair routine accepts negative values of foreground and back‐
178 ground color to support the use_default_colors extension, but only if
179 that routine has been first invoked.
180 The assumption that COLOR_BLACK is the default background color for all
182 terminals can be modified using the assume_default_colors extension.
183 This implementation checks the pointers, e.g., for the values returned
185 by color_content and pair_content, and will treat those as optional pa‐
186 rameters when null.
187
189 curses(3X), curs_initscr(3X), curs_attr(3X), default_colors(3X)
190 curs_color(3X)