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+ * Author: Thomas E. Dickey
+ * @Id: new_pair.3x,v 1.13 2018/07/28 22:19:56 tom Exp @
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+<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>&lt;curses.h&gt;</STRONG>
+
+ <STRONG>int</STRONG> <STRONG>alloc_pair(int</STRONG> <STRONG>fg,</STRONG> <STRONG>int</STRONG> <STRONG>bg);</STRONG>
+ <STRONG>int</STRONG> <STRONG>find_pair(int</STRONG> <STRONG>fg,</STRONG> <STRONG>int</STRONG> <STRONG>bg);</STRONG>
+ <STRONG>int</STRONG> <STRONG>free_pair(int</STRONG> <STRONG>pair);</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 fore-
+ ground/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> inde-
+ pendently, 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 pal-
+ ette on a terminal. If the library does not keep track of the <EM>com-</EM>
+ <EM>binations</EM> of colors which are displayed, it will be inefficient.
+
+ <STRONG>o</STRONG> For simple terminal emulators with only a few dozen color combina-
+ tions, 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 appli-
+ cation).
+
+ 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 back-
+ ground color, and checks if that color combination is already associ-
+ ated 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 allo-
+ cated 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> capa-
+ bility. 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. Oth-
+ erwise 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>