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<H1 class="no-header">curs_bkgd 3x</H1>
<PRE>
<STRONG><A HREF="curs_bkgd.3x.html">curs_bkgd(3x)</A></STRONG> <STRONG><A HREF="curs_bkgd.3x.html">curs_bkgd(3x)</A></STRONG>
</PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
<STRONG>bkgdset</STRONG>, <STRONG>wbkgdset</STRONG>, <STRONG>bkgd</STRONG>, <STRONG>wbkgd</STRONG>, <STRONG>getbkgd</STRONG> - <STRONG>curses</STRONG> window background
manipulation routines
</PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
<STRONG>#include</STRONG> <STRONG><curses.h></STRONG>
<STRONG>void</STRONG> <STRONG>bkgdset(chtype</STRONG> <EM>ch</EM><STRONG>);</STRONG>
<STRONG>void</STRONG> <STRONG>wbkgdset(WINDOW</STRONG> <STRONG>*</STRONG><EM>win,</EM> <EM>chtype</EM> <EM>ch</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>bkgd(chtype</STRONG> <EM>ch</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>wbkgd(WINDOW</STRONG> <STRONG>*</STRONG><EM>win</EM><STRONG>,</STRONG> <STRONG>chtype</STRONG> <EM>ch</EM><STRONG>);</STRONG>
<STRONG>chtype</STRONG> <STRONG>getbkgd(WINDOW</STRONG> <STRONG>*</STRONG><EM>win</EM><STRONG>);</STRONG>
</PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
</PRE><H3><a name="h3-bkgdset">bkgdset</a></H3><PRE>
The <STRONG>bkgdset</STRONG> and <STRONG>wbkgdset</STRONG> routines manipulate the background of the
named window. The window background is a <STRONG>chtype</STRONG> consisting of any com-
bination of attributes (i.e., rendition) and a character. The
attribute part of the background is combined (OR'ed) with all non-blank
characters that are written into the window with <STRONG>waddch</STRONG>. Both the
character and attribute parts of the background are combined with the
blank characters. The background becomes a property of the character
and moves with the character through any scrolling and insert/delete
line/character operations.
To the extent possible on a particular terminal, the attribute part of
the background is displayed as the graphic rendition of the character
put on the screen.
</PRE><H3><a name="h3-bkgd">bkgd</a></H3><PRE>
The <STRONG>bkgd</STRONG> and <STRONG>wbkgd</STRONG> functions set the background property of the current
or specified window and then apply this setting to every character
position in that window. According to X/Open Curses, it should do
this:
<STRONG>o</STRONG> The rendition of every character on the screen is changed to the
new background rendition.
<STRONG>o</STRONG> Wherever the former background character appears, it is changed to
the new background character.
Neither X/Open Curses nor the SVr4 manual pages give details about the
way the rendition of characters on the screen is updated when <STRONG>bkgd</STRONG> or
<STRONG>wbkgd</STRONG> is used to change the background character.
This implementation, like SVr4 curses, does not store the background
and window attribute contributions to each cell separately. It updates
the rendition by comparing the character, non-color attributes and col-
ors contained in the background. For each cell in the window, whether
or not it is blank:
<STRONG>o</STRONG> The library first compares the <EM>character</EM>, and if it matches the
current character part of the background, it replaces that with the
new background character.
<STRONG>o</STRONG> The library then checks if the cell uses color, i.e., 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 char-
acter.
<STRONG>o</STRONG> If the cell uses color, and that matches the color in the current
background, the library removes attributes which may have come from
the current background and adds attributes from the new background.
It finishes by setting the cell to use the color from the new back-
ground.
<STRONG>o</STRONG> If the cell uses color, and that does not match the color in the
current background, the library updates only the non-color
attributes, first removing those which may have come from the cur-
rent background, and then adding attributes from the new back-
ground.
If the background's character value is zero, a space is assumed.
If the terminal does not support color, or if color has not been
started with <STRONG>start_color</STRONG>, the new background character's color
attribute will be ignored.
</PRE><H3><a name="h3-getbkgd">getbkgd</a></H3><PRE>
The <STRONG>getbkgd</STRONG> function returns the given window's current background
character/attribute pair.
</PRE><H2><a name="h2-RETURN-VALUE">RETURN VALUE</a></H2><PRE>
These functions are described in the XSI Curses standard, Issue 4. It
specifies that <STRONG>bkgd</STRONG> and <STRONG>wbkgd</STRONG> return <STRONG>ERR</STRONG> on failure, but gives no fail-
ure conditions.
The routines <STRONG>bkgd</STRONG> and <STRONG>wbkgd</STRONG> return the integer <STRONG>OK</STRONG>, unless the library
has not been initialized.
In contrast, the SVr4.0 manual says <STRONG>bkgd</STRONG> and <STRONG>wbkgd</STRONG> may return <STRONG>OK</STRONG> "or a
non-negative integer if <STRONG>immedok</STRONG> is set", which refers to the return
value from <STRONG>wrefresh</STRONG> (used to implement the immediate repainting). The
SVr4 curses <STRONG>wrefresh</STRONG> returns the number of characters written to the
screen during the refresh. This implementation does not do that.
</PRE><H2><a name="h2-NOTES">NOTES</a></H2><PRE>
Note that <STRONG>bkgdset</STRONG> and <STRONG>bkgd</STRONG> may be macros.
X/Open Curses mentions that the character part of the background must
be a single-byte value. This implementation, like SVr4, checks to
ensure that, and will reuse the old background character if the check
fails.
</PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
These functions are described in the XSI Curses standard, Issue 4
(X/Open Curses).
</PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
<STRONG><A HREF="ncurses.3x.html">curses(3x)</A></STRONG>, <STRONG><A HREF="curs_addch.3x.html">curs_addch(3x)</A></STRONG>, <STRONG><A HREF="curs_attr.3x.html">curs_attr(3x)</A></STRONG>, <STRONG><A HREF="curs_outopts.3x.html">curs_outopts(3x)</A></STRONG>
<STRONG><A HREF="curs_bkgd.3x.html">curs_bkgd(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-bkgdset">bkgdset</a></li>
<li><a href="#h3-bkgd">bkgd</a></li>
<li><a href="#h3-getbkgd">getbkgd</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-SEE-ALSO">SEE ALSO</a></li>
</ul>
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