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, except that if default colors are used (see use_de‐
58 fault_colors) the upper limit is adjusted to allow for extra pairs
59 which use a default color in foreground and/or background.
60 - The value of the second and third arguments must be between 0 and
62 COLORS. Color pair 0 is assumed to be white on black, but is ac‐
63 tually whatever the terminal implements before color is initial‐
64 ized. It cannot be modified by the application.
65 If the color-pair was previously initialized, the screen is refreshed
67 and all occurrences of that color-pair are changed to the new defini‐
68 tion.
69 As an extension, ncurses allows you to set color pair 0 via the as‐
71 sume_default_colors routine, or to specify the use of default colors
72 (color number -1) if you first invoke the use_default_colors routine.
73 The init_color routine changes the definition of a color. It takes
75 four arguments: the number of the color to be changed followed by three
76 RGB values (for the amounts of red, green, and blue components). The
77 value of the first argument must be between 0 and COLORS. (See the
78 section Colors for the default color index.) Each of the last three
79 arguments must be a value between 0 and 1000. When init_color is used,
80 all occurrences of that color on the screen immediately change to the
81 new definition.
82 The has_colors routine requires no arguments. It returns TRUE if the
84 terminal can manipulate colors; otherwise, it returns FALSE. This rou‐
85 tine facilitates writing terminal-independent programs. For example, a
86 programmer can use it to decide whether to use color or some other
87 video attribute.
88 The can_change_color routine requires no arguments. It returns TRUE if
90 the terminal supports colors and can change their definitions; other,
91 it returns FALSE. This routine facilitates writing terminal-indepen‐
92 dent programs.
93 The color_content routine gives programmers a way to find the intensity
95 of the red, green, and blue (RGB) components in a color. It requires
96 four arguments: the color number, and three addresses of shorts for
97 storing the information about the amounts of red, green, and blue com‐
98 ponents in the given color. The value of the first argument must be
99 between 0 and COLORS. The values that are stored at the addresses
100 pointed to by the last three arguments are between 0 (no component) and
101 1000 (maximum amount of component).
102 The pair_content routine allows programmers to find out what colors a
104 given color-pair consists of. It requires three arguments: the color-
105 pair number, and two addresses of shorts for storing the foreground and
106 the background color numbers. The value of the first argument must be
107 between 1 and COLOR_PAIRS-1. The values that are stored at the ad‐
108 dresses pointed to by the second and third arguments are between 0 and
109 COLORS.
110 Colors
112 In <curses.h> the following macros are defined. These are the default
113 colors. curses also assumes that COLOR_BLACK is the default background
114 color for all terminals.
115 COLOR_BLACK
117 COLOR_RED
118 COLOR_GREEN
119 COLOR_YELLOW
120 COLOR_BLUE
121 COLOR_MAGENTA
122 COLOR_CYAN
123 COLOR_WHITE
124
126 The routines can_change_color() and has_colors() return TRUE or FALSE.
127 All other routines return the integer ERR upon failure and an OK (SVr4
129 specifies only "an integer value other than ERR") upon successful com‐
130 pletion.
131 X/Open defines no error conditions. This implementation will return
133 ERR on attempts to use color values outside the range 0 to COLORS-1
134 (except for the default colors extension), or use color pairs outside
135 the range 0 to COLOR_PAIR-1. Color values used in init_color must be
136 in the range 0 to 1000. An error is returned from all functions if the
137 terminal has not been initialized. An error is returned from secondary
138 functions such as init_pair if start_color was not called.
139 init_color
141 returns an error if the terminal does not support this fea‐
142 ture, e.g., if the initialize_color capability is absent
143 from the terminal description.
144 start_color
146 returns an error If the color table cannot be allocated.
147
149 In the ncurses implementation, there is a separate color activation
150 flag, color palette, color pairs table, and associated COLORS and COL‐
151 OR_PAIRS counts for each screen; the start_color function only affects
152 the current screen. The SVr4/XSI interface is not really designed with
153 this in mind, and historical implementations may use a single shared
154 color palette.
155 Note that setting an implicit background color via a color pair affects
157 only character cells that a character write operation explicitly touch‐
158 es. To change the background color used when parts of a window are
159 blanked by erasing or scrolling operations, see curs_bkgd(3X).
160 Several caveats apply on 386 and 486 machines with VGA-compatible
162 graphics:
163 - COLOR_YELLOW is actually brown. To get yellow, use COLOR_YELLOW
165 combined with the A_BOLD attribute.
166 - The A_BLINK attribute should in theory cause the background to go
168 bright. This often fails to work, and even some cards for which
169 it mostly works (such as the Paradise and compatibles) do the
170 wrong thing when you try to set a bright "yellow" background (you
171 get a blinking yellow foreground instead).
172 - Color RGB values are not settable.
174
176 This implementation satisfies XSI Curses's minimum maximums for COLORS
177 and COLOR_PAIRS.
178 The init_pair routine accepts negative values of foreground and back‐
180 ground color to support the use_default_colors extension, but only if
181 that routine has been first invoked.
182 The assumption that COLOR_BLACK is the default background color for all
184 terminals can be modified using the assume_default_colors extension.
185 This implementation checks the pointers, e.g., for the values returned
187 by color_content and pair_content, and will treat those as optional pa‐
188 rameters when null.
189
191 curses(3X), curs_initscr(3X), curs_attr(3X), default_colors(3X)
192 curs_color(3X)