1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
|
<!--
****************************************************************************
* Copyright 2018-2020,2021 Thomas E. Dickey *
* Copyright 2017 Free Software Foundation, Inc. *
* *
* Permission is hereby granted, free of charge, to any person obtaining a *
* copy of this software and associated documentation files (the *
* "Software"), to deal in the Software without restriction, including *
* without limitation the rights to use, copy, modify, merge, publish, *
* distribute, distribute with modifications, sublicense, and/or sell *
* copies of the Software, and to permit persons to whom the Software is *
* furnished to do so, subject to the following conditions: *
* *
* The above copyright notice and this permission notice shall be included *
* in all copies or substantial portions of the Software. *
* *
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS *
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF *
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. *
* IN NO EVENT SHALL THE ABOVE COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, *
* DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR *
* OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR *
* THE USE OR OTHER DEALINGS IN THE SOFTWARE. *
* *
* Except as contained in this notice, the name(s) of the above copyright *
* holders shall not be used in advertising or otherwise to promote the *
* sale, use or other dealings in this Software without prior written *
* authorization. *
****************************************************************************
* Author: Thomas E. Dickey
* @Id: new_pair.3x,v 1.16 2021/06/17 21:26:02 tom Exp @
-->
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN">
<HTML>
<HEAD>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
<meta name="generator" content="Manpage converted by man2html - see https://invisible-island.net/scripts/readme.html#others_scripts">
<TITLE>new_pair 3x</TITLE>
<link rel="author" href="mailto:bug-ncurses@gnu.org">
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
</HEAD>
<BODY>
<H1 class="no-header">new_pair 3x</H1>
<PRE>
<STRONG><A HREF="new_pair.3x.html">new_pair(3x)</A></STRONG> <STRONG><A HREF="new_pair.3x.html">new_pair(3x)</A></STRONG>
</PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
<STRONG>alloc_pair</STRONG>, <STRONG>find_pair</STRONG>, <STRONG>free_pair</STRONG> - new curses color-pair functions
</PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
<STRONG>#include</STRONG> <STRONG><curses.h></STRONG>
<STRONG>int</STRONG> <STRONG>alloc_pair(int</STRONG> <EM>fg</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>bg</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>find_pair(int</STRONG> <EM>fg</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>bg</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>free_pair(int</STRONG> <EM>pair</EM><STRONG>);</STRONG>
</PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
These functions are an extension to the curses library. They permit an
application to dynamically allocate a color pair using the
foreground/background colors rather than assign a fixed color pair
number, and return an unused pair to the pool.
The number of colors may be related to the number of possible color
pairs for a given terminal, or it may not:
<STRONG>o</STRONG> While almost all terminals allow setting the color <EM>attributes</EM>
independently, it is unlikely that your terminal allows you to
modify the attributes of a given character cell without rewriting
it. That is, the foreground and background colors are applied as a
pair.
<STRONG>o</STRONG> Color pairs are the curses library's way of managing a color
palette on a terminal. If the library does not keep track of the
<EM>combinations</EM> of colors which are displayed, it will be inefficient.
<STRONG>o</STRONG> For simple terminal emulators with only a few dozen color
combinations, it is convenient to use the maximum number of
combinations as the limit on color pairs:
<STRONG>COLORS</STRONG> <EM>*</EM> <STRONG>COLORS</STRONG>
<STRONG>o</STRONG> Terminals which support <EM>default</EM> <EM>colors</EM> distinct from "ANSI colors"
add to the possible combinations, producing this total:
<EM>(</EM> <STRONG>COLORS</STRONG> <EM>+</EM> <EM>1</EM> <EM>)</EM> <EM>*</EM> <EM>(</EM> <STRONG>COLORS</STRONG> <EM>+</EM> <EM>1</EM> <EM>)</EM>
<STRONG>o</STRONG> An application might use up to a few dozen color pairs to implement
a predefined color scheme.
Beyond that lies in the realm of programs using the foreground and
background colors for "ASCII art" (or some other non-textual
application).
Also beyond those few dozen pairs, the required size for a table to
represent the combinations grows rapidly with an increasing number
of colors.
These functions allow a developer to let the screen library manage
color pairs.
</PRE><H3><a name="h3-alloc_pair">alloc_pair</a></H3><PRE>
The <STRONG>alloc_pair</STRONG> function accepts parameters for foreground and
background color, and checks if that color combination is already
associated with a color pair.
<STRONG>o</STRONG> If the combination already exists, <STRONG>alloc_pair</STRONG> returns the existing
pair.
<STRONG>o</STRONG> If the combination does not exist, <STRONG>alloc_pair</STRONG> allocates a new color
pair and returns that.
<STRONG>o</STRONG> If the table fills up, <STRONG>alloc_pair</STRONG> discards the least-recently
allocated entry using <STRONG>free_pair</STRONG> and allocates a new color pair.
All of the color pairs are allocated from a table of possible color
pairs. The size of the table is determined by the terminfo <EM>pairs</EM>
capability. The table is shared with <STRONG>init_pair</STRONG>; in fact <STRONG>alloc_pair</STRONG>
calls <STRONG>init_pair</STRONG> after updating the ncurses library's fast index to the
colors versus color pairs.
</PRE><H3><a name="h3-find_pair">find_pair</a></H3><PRE>
The <STRONG>find_pair</STRONG> function accepts parameters for foreground and background
color, and checks if that color combination is already associated with
a color pair, returning the pair number if it has been allocated.
Otherwise it returns -1.
</PRE><H3><a name="h3-free_pair">free_pair</a></H3><PRE>
Marks the given color pair as unused, i.e., like color pair 0.
</PRE><H2><a name="h2-RETURN-VALUE">RETURN VALUE</a></H2><PRE>
The <STRONG>alloc_pair</STRONG> function returns a color pair number in the range 1
through <STRONG>COLOR_PAIRS</STRONG>-1, unless it encounters an error updating its fast
index to the color pair values, preventing it from allocating a color
pair. In that case, it returns -1.
The <STRONG>find_pair</STRONG> function returns a color pair number if the given color
combination has been associated with a color pair, or -1 if not.
Likewise, <STRONG>free_pair</STRONG> returns <STRONG>OK</STRONG> unless it encounters an error updating
the fast index or if no such color pair is in use.
</PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
These routines are specific to ncurses. They were not supported on
Version 7, BSD or System V implementations. It is recommended that any
code depending on them be conditioned using NCURSES_VERSION.
</PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
<STRONG><A HREF="curs_color.3x.html">curs_color(3x)</A></STRONG>.
</PRE><H2><a name="h2-AUTHOR">AUTHOR</a></H2><PRE>
Thomas Dickey.
<STRONG><A HREF="new_pair.3x.html">new_pair(3x)</A></STRONG>
</PRE>
<div class="nav">
<ul>
<li><a href="#h2-NAME">NAME</a></li>
<li><a href="#h2-SYNOPSIS">SYNOPSIS</a></li>
<li><a href="#h2-DESCRIPTION">DESCRIPTION</a>
<ul>
<li><a href="#h3-alloc_pair">alloc_pair</a></li>
<li><a href="#h3-find_pair">find_pair</a></li>
<li><a href="#h3-free_pair">free_pair</a></li>
</ul>
</li>
<li><a href="#h2-RETURN-VALUE">RETURN VALUE</a></li>
<li><a href="#h2-PORTABILITY">PORTABILITY</a></li>
<li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>
<li><a href="#h2-AUTHOR">AUTHOR</a></li>
</ul>
</div>
</BODY>
</HTML>
|
