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Dickey + * @Id: new_pair.3x,v 1.14 2020/02/02 23:34:34 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> <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> |