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<H1 class="no-header">curs_bkgrnd 3x 2025-08-23 ncurses 6.6 Library calls</H1>
<PRE>
<STRONG><A HREF="curs_bkgrnd.3x.html">curs_bkgrnd(3x)</A></STRONG> Library calls <STRONG><A HREF="curs_bkgrnd.3x.html">curs_bkgrnd(3x)</A></STRONG>
</PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
<STRONG>bkgrnd</STRONG>, <STRONG>wbkgrnd</STRONG>, <STRONG>bkgrndset</STRONG>, <STRONG>wbkgrndset</STRONG>, <STRONG>getbkgrnd</STRONG>, <STRONG>wgetbkgrnd</STRONG> -
manipulate background of a <EM>curses</EM> window of wide characters
</PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
<STRONG>#include</STRONG> <STRONG><curses.h></STRONG>
<STRONG>int</STRONG> <STRONG>bkgrnd(const</STRONG> <STRONG>cchar_t</STRONG> <STRONG>*</STRONG><EM>wch</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>wbkgrnd(WINDOW</STRONG> <STRONG>*</STRONG><EM>win</EM><STRONG>,</STRONG> <STRONG>const</STRONG> <STRONG>cchar_t</STRONG> <STRONG>*</STRONG><EM>wch</EM><STRONG>);</STRONG>
<STRONG>void</STRONG> <STRONG>bkgrndset(const</STRONG> <STRONG>cchar_t</STRONG> <STRONG>*</STRONG><EM>wch</EM><STRONG>);</STRONG>
<STRONG>void</STRONG> <STRONG>wbkgrndset(WINDOW</STRONG> <STRONG>*</STRONG><EM>win</EM><STRONG>,</STRONG> <STRONG>const</STRONG> <STRONG>cchar_t</STRONG> <STRONG>*</STRONG><EM>wch</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>getbkgrnd(cchar_t</STRONG> <STRONG>*</STRONG><EM>wch</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>wgetbkgrnd(WINDOW</STRONG> <STRONG>*</STRONG><EM>win</EM><STRONG>,</STRONG> <STRONG>cchar_t</STRONG> <STRONG>*</STRONG><EM>wch</EM><STRONG>);</STRONG>
</PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
Every <EM>curses</EM> window has a <EM>background</EM> <EM>character</EM> property: in the
library's wide configuration, it is a <EM>curses</EM> complex character
(<EM>cchar</EM><STRONG>_</STRONG><EM>t</EM>) that combines a set of attributes (and, if colors are
enabled, a color pair identifier) with a character code. When erasing
(parts of) a window, <EM>curses</EM> replaces the erased cells with the
background character.
<EM>curses</EM> also uses the background character when writing characters to a
populated window.
<STRONG>o</STRONG> The attribute part of the background character combines with all
non-blank character cells in the window, as populated by the
<STRONG><A HREF="curs_add_wch.3x.html">wadd_wch(3x)</A></STRONG> and <STRONG><A HREF="curs_ins_wch.3x.html">wins_wch(3x)</A></STRONG> families of functions (and those that
call them).
<STRONG>o</STRONG> Both the character code and attributes of the background character
combine with blank character cells in the window.
The background character's set of attributes becomes a property of the
character cell and move with it through any scrolling and insert/delete
line/character operations. To the extent possible on the terminal
type, <EM>curses</EM> displays the attributes of the background character as the
graphic rendition of a character cell on the display.
</PRE><H3><a name="h3-bkgrnd_wbkgrnd">bkgrnd, wbkgrnd</a></H3><PRE>
<STRONG>bkgrnd</STRONG> and <STRONG>wbkgrnd</STRONG> set the background property of <STRONG>stdscr</STRONG> or the
specified window and then apply this setting to every character cell in
that window.
<STRONG>o</STRONG> The rendition of every character in the window changes to the new
background rendition.
<STRONG>o</STRONG> Wherever the former background character appears, it changes to the
new background character.
<EM>ncurses</EM> updates the rendition of each character cell by comparing the
character, non-color attributes, and color pair selection. The library
applies to following procedure to each cell in the window, whether or
not it is blank.
<STRONG>o</STRONG> <EM>ncurses</EM> first compares the cell's character to the previously
specified background character; if they match, <EM>ncurses</EM> writes the
new background character to the cell.
<STRONG>o</STRONG> <EM>ncurses</EM> then checks whether the cell uses color; that is, its color
pair value is nonzero. If not, it simply replaces the attributes
and color pair in the cell with those from the new background
character.
<STRONG>o</STRONG> If the cell uses color, and its background color matches that of
the current window background, <EM>ncurses</EM> removes attributes that may
have come from the current background and adds those from the new
background. It finishes by setting the cell's background to use
the new window background color.
<STRONG>o</STRONG> If the cell uses color, and its background color does not match
that of the current window background, <EM>ncurses</EM> updates only the
non-color attributes, first removing those that may have come from
the current background, and then adding attributes from the new
background.
If the new background's character is non-spacing, <EM>ncurses</EM> reuses the
old background character, except for one special case: <EM>ncurses</EM> treats a
background character code of zero (0) as a space.
If the terminal does not support color, or if color has not been
initialized with <STRONG><A HREF="curs_color.3x.html">start_color(3x)</A></STRONG>, <EM>ncurses</EM> ignores the new background
character's color pair selection.
</PRE><H3><a name="h3-bkgrndset_wbkgrndset">bkgrndset, wbkgrndset</a></H3><PRE>
<STRONG>bkgrndset</STRONG> and <STRONG>wbkgrndset</STRONG> manipulate the background of the applicable
window, without updating the character cells as <STRONG>bkgrnd</STRONG> and <STRONG>wbkgrnd</STRONG> do;
only future writes reflect the updated background.
</PRE><H3><a name="h3-getbkgrnd_wgetbkgrnd">getbkgrnd, wgetbkgrnd</a></H3><PRE>
<STRONG>getbkgrnd</STRONG> and <STRONG>wgetbkgrnd</STRONG> respectively obtain <STRONG>stdscr</STRONG>'s or the given
window's background character, attributes, and color pair, and store it
in their <EM>wch</EM> argument.
</PRE><H2><a name="h2-RETURN-VALUE">RETURN VALUE</a></H2><PRE>
<STRONG>bkgrndset</STRONG> and <STRONG>wbkgrndset</STRONG> do not return a value.
Functions returning an <EM>int</EM> return <STRONG>ERR</STRONG> upon failure and <STRONG>OK</STRONG> upon success.
In <EM>ncurses</EM>, failure occurs if
<STRONG>o</STRONG> the <EM>curses</EM> screen has not been initialized,
<STRONG>o</STRONG> <EM>win</EM> is <EM>NULL</EM>, or
<STRONG>o</STRONG> <EM>wch</EM> is <EM>NULL</EM>.
</PRE><H2><a name="h2-NOTES">NOTES</a></H2><PRE>
<STRONG>bkgrnd</STRONG>, <STRONG>bkgrndset</STRONG>, and <STRONG>getbkgrnd</STRONG> may be implemented as macros.
Unlike their counterparts in the non-wide-character configuration of
<EM>ncurses</EM>, <STRONG>getbkgrnd</STRONG> and <STRONG>wgetbkgrnd</STRONG> store the background character in a
modifiable <EM>cchar</EM><STRONG>_</STRONG><EM>t</EM> parameter, rather than supplying it as the return
value.
</PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
X/Open Curses Issue 4 describes these functions. It specifies no error
conditions for them.
X/Open Curses does not provide details of how the rendition is updated.
<EM>ncurses</EM> follows the approach used in SVr4 <EM>curses</EM>'s non-wide functions
for manipulating the window background.
</PRE><H2><a name="h2-HISTORY">HISTORY</a></H2><PRE>
X/Open Curses Issue 4 (1995) initially specified these functions.
</PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
<STRONG><A HREF="curs_bkgd.3x.html">curs_bkgd(3x)</A></STRONG> describes the corresponding functions in the non-wide-
character configuration of <EM>ncurses</EM>.
<STRONG><A HREF="ncurses.3x.html">curses(3x)</A></STRONG>, <STRONG><A HREF="curs_add_wch.3x.html">curs_add_wch(3x)</A></STRONG>, <STRONG><A HREF="curs_attr.3x.html">curs_attr(3x)</A></STRONG>
ncurses 6.6 2025-08-23 <STRONG><A HREF="curs_bkgrnd.3x.html">curs_bkgrnd(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-bkgrnd_wbkgrnd">bkgrnd, wbkgrnd</a></li>
<li><a href="#h3-bkgrndset_wbkgrndset">bkgrndset, wbkgrndset</a></li>
<li><a href="#h3-getbkgrnd_wgetbkgrnd">getbkgrnd, wgetbkgrnd</a></li>
</ul>
</li>
<li><a href="#h2-RETURN-VALUE">RETURN VALUE</a></li>
<li><a href="#h2-NOTES">NOTES</a></li>
<li><a href="#h2-PORTABILITY">PORTABILITY</a></li>
<li><a href="#h2-HISTORY">HISTORY</a></li>
<li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>
</ul>
</div>
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