1new_pair(3X) new_pair(3X)
2
6 alloc_pair, find_pair, free_pair - new curses color-pair functions
7
9 #include <curses.h>
10 int alloc_pair(int fg, int bg);
12 int find_pair(int fg, int bg);
13 int free_pair(int pair);
14
16 These functions are an extension to the curses library. They permit an
17 application to dynamically allocate a color pair using the fore‐
18 ground/background colors rather than assign a fixed color pair number,
19 and return an unused pair to the pool.
20 The number of colors may be related to the number of possible color
22 pairs for a given terminal, or it may not:
23 · While almost all terminals allow setting the color attributes inde‐
25 pendently, it is unlikely that your terminal allows you to modify
26 the attributes of a given character cell without rewriting it.
27 That is, the foreground and background colors are applied as a
28 pair.
29 · Color pairs are the curses library's way of managing a color pal‐
31 ette on a terminal. If the library does not keep track of the com‐
32 binations of colors which are displayed, it will be inefficient.
33 · For simple terminal emulators with only a few dozen color combina‐
35 tions, it is convenient to use the maximum number of combinations
36 as the limit on color pairs:
37 COLORS * COLORS
39 · Terminals which support default colors distinct from “ANSI colors”
41 add to the possible combinations, producing this total:
42 ( COLORS + 1 ) * ( COLORS + 1 )
44 · An application might use up to a few dozen color pairs to implement
46 a predefined color scheme.
47 Beyond that lies in the realm of programs using the foreground and
49 background colors for “ASCII art” (or some other non-textual appli‐
50 cation).
51 Also beyond those few dozen pairs, the required size for a table to
53 represent the combinations grows rapidly with an increasing number
54 of colors.
55 These functions allow a developer to let the screen library manage
57 color pairs.
58 alloc_pair
60 The alloc_pair function accepts parameters for foreground and back‐
61 ground color, and checks if that color combination is already associ‐
62 ated with a color pair.
63 · If the combination already exists, alloc_pair returns the existing
65 pair.
66 · If the combination does not exist, alloc_pair allocates a new color
68 pair and returns that.
69 · If the table fills up, alloc_pair discards the least-recently allo‐
71 cated entry using free_pair and allocates a new color pair.
72 All of the color pairs are allocated from a table of possible color
74 pairs. The size of the table is determined by the terminfo pairs capa‐
75 bility. The table is shared with init_pair; in fact alloc_pair calls
76 init_pair after updating the ncurses library's fast index to the colors
77 versus color pairs.
78 find_pair
80 The find_pair function accepts parameters for foreground and background
81 color, and checks if that color combination is already associated with
82 a color pair, returning the pair number if it has been allocated. Oth‐
83 erwise it returns -1.
84 free_pair
86 Marks the given color pair as unused, i.e., like color pair 0.
87
89 The alloc_pair function returns a color pair number in the range 1
90 through COLOR_PAIRS-1, unless it encounters an error updating its fast
91 index to the color pair values, preventing it from allocating a color
92 pair. In that case, it returns -1.
93 The find_pair function returns a color pair number if the given color
95 combination has been associated with a color pair, or -1 if not.
96 Likewise, free_pair returns OK unless it encounters an error updating
98 the fast index or if no such color pair is in use.
99
101 These routines are specific to ncurses. They were not supported on
102 Version 7, BSD or System V implementations. It is recommended that any
103 code depending on them be conditioned using NCURSES_VERSION.
104
106 curs_color(3X).
107
109 Thomas Dickey.
110 new_pair(3X)