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29 * Author: Thomas E. Dickey
30 * @Id: new_pair.3x,v 1.9 2017/03/13 21:21:34 tom Exp @
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42 <H1 class="no-header">new_pair 3x</H1>
44 <STRONG><A HREF="new_pair.3x.html">new_pair(3x)</A></STRONG> <STRONG><A HREF="new_pair.3x.html">new_pair(3x)</A></STRONG>
49 </PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
50 <STRONG>alloc_pair</STRONG>, <STRONG>find_pair</STRONG>, <STRONG>free_pair</STRONG> - new curses color-pair
54 </PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
55 <STRONG>#include</STRONG> <STRONG><curses.h></STRONG>
57 <STRONG>int</STRONG> <STRONG>alloc_pair(int</STRONG> <STRONG>fg,</STRONG> <STRONG>int</STRONG> <STRONG>bg);</STRONG>
58 <STRONG>int</STRONG> <STRONG>find_pair(int</STRONG> <STRONG>fg,</STRONG> <STRONG>int</STRONG> <STRONG>bg);</STRONG>
59 <STRONG>int</STRONG> <STRONG>free_pair(int</STRONG> <STRONG>pair);</STRONG>
62 </PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
63 These functions are an extension to the curses library.
64 They permit an application to dynamically allocate a color
65 pair using the foreground/background colors rather than
66 assign a fixed color pair number, and return an unused
69 The number of colors may be related to the number of pos-
70 sible color pairs for a given terminal, or it may not:
72 <STRONG>o</STRONG> While almost all terminals allow setting the color
73 <EM>attributes</EM> independently, it is unlikely that your
74 terminal allows you to modify the attributes of a
75 given character cell without rewriting it. That is,
76 the foreground and background colors are applied as a
79 <STRONG>o</STRONG> Color pairs are the curses library's way of managing a
80 color palette on a terminal. If the library does not
81 keep track of the <EM>combinations</EM> of colors which are
82 displayed, it will be inefficient.
84 <STRONG>o</STRONG> For simple terminal emulators with only a few dozen
85 color combinations, it is convenient to use the maxi-
86 mum number of combinations as the limit on color
89 <STRONG>COLORS</STRONG> <EM>*</EM> <STRONG>COLORS</STRONG>
91 <STRONG>o</STRONG> Terminals which support <EM>default</EM> <EM>colors</EM> distinct from
92 "ANSI colors" add to the possible combinations, pro-
95 <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>
97 <STRONG>o</STRONG> An application might use up to a few dozen color pairs
98 to implement a predefined color scheme.
100 Beyond that lies in the realm of programs using the
101 foreground and background colors for "ASCII art" (or
102 some other non-textual application).
104 Also beyond those few dozen pairs, the required size
105 for a table to represent the combinations grows
106 rapidly with an increasing number of colors.
108 These functions allow a developer to let the screen
109 library manage color pairs.
112 </PRE><H3><a name="h3-alloc_pair">alloc_pair</a></H3><PRE>
113 The <STRONG>alloc_pair</STRONG> function accepts parameters for foreground
114 and background color, and checks if that color combination
115 is already associated with a color pair.
117 <STRONG>o</STRONG> If the combination already exists, <STRONG>alloc_pair</STRONG> returns
120 <STRONG>o</STRONG> If the combination does not exist, <STRONG>alloc_pair</STRONG> allo-
121 cates a new color pair and returns that.
123 <STRONG>o</STRONG> If the table fills up, <STRONG>alloc_pair</STRONG> discards the least-
124 recently allocated entry using <STRONG>free_pair</STRONG> and allocates
127 All of the color pairs are allocated from a table of pos-
128 sible color pairs. The size of the table is determined by
129 the terminfo <EM>pairs</EM> capability. The table is shared with
130 <STRONG>init_pair</STRONG>; in fact <STRONG>alloc_pair</STRONG> calls <STRONG>init_pair</STRONG> after updat-
131 ing the ncurses library's fast index to the colors versus
135 </PRE><H3><a name="h3-find_pair">find_pair</a></H3><PRE>
136 The <STRONG>find_pair</STRONG> function accepts parameters for foreground
137 and background color, and checks if that color combination
138 is already associated with a color pair, returning the
139 pair number if it has been allocated. Otherwise it
143 </PRE><H3><a name="h3-free_pair">free_pair</a></H3><PRE>
144 Marks the given color pair as unused, i.e., like color
148 </PRE><H2><a name="h2-RETURN-VALUE">RETURN VALUE</a></H2><PRE>
149 The <STRONG>alloc_pair</STRONG> function returns a color pair number in the
150 range 1 through <STRONG>COLOR_PAIRS</STRONG>-1, unless it encounters an
151 error updating its fast index to the color pair values,
152 preventing it from allocating a color pair. In that case,
155 The <STRONG>find_pair</STRONG> function returns a color pair number if the
156 given color combination has been associated with a color
159 Likewise, <STRONG>free_pair</STRONG> returns <STRONG>OK</STRONG> unless it encounters an
160 error updating the fast index or if no such color pair is
164 </PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
165 These routines are specific to ncurses. They were not
166 supported on Version 7, BSD or System V implementations.
167 It is recommended that any code depending on them be con-
168 ditioned using NCURSES_VERSION.
171 </PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
172 <STRONG><A HREF="init_pair.3x.html">init_pair(3x)</A></STRONG>.
175 </PRE><H2><a name="h2-AUTHOR">AUTHOR</a></H2><PRE>
180 <STRONG><A HREF="new_pair.3x.html">new_pair(3x)</A></STRONG>
184 <li><a href="#h2-NAME">NAME</a></li>
185 <li><a href="#h2-SYNOPSIS">SYNOPSIS</a></li>
186 <li><a href="#h2-DESCRIPTION">DESCRIPTION</a>
188 <li><a href="#h3-alloc_pair">alloc_pair</a></li>
189 <li><a href="#h3-find_pair">find_pair</a></li>
190 <li><a href="#h3-free_pair">free_pair</a></li>
193 <li><a href="#h2-RETURN-VALUE">RETURN VALUE</a></li>
194 <li><a href="#h2-PORTABILITY">PORTABILITY</a></li>
195 <li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>
196 <li><a href="#h2-AUTHOR">AUTHOR</a></li>