doc/html/man/new_pair.3x.html - master - githubmirror/ncurses

doc/html/man/new_pair.3x.html
187 строк9 KB
Thomas E. Dickey
ncurses 6.3 - patch 20220212
13 фев 2022, 05:28
13 фев 2022, 05:2816fbf3f
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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> <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  <STRONG>pairs</STRONG>
       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>
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<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>
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