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+ * @Id: new_pair.3x,v 1.9 2017/03/13 21:21:34 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><curses.h></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 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 pos-
+ sible 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 maxi-
+ mum 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, pro-
+ ducing 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> allo-
+ cates 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 pos-
+ sible 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 updat-
+ ing 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 con-
+ ditioned using NCURSES_VERSION.
+
+
+</PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
+ <STRONG><A HREF="init_pair.3x.html">init_pair(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>
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