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37 <TITLE>curs_bkgrnd 3x 2024-04-20 ncurses 6.4 Library calls</TITLE>
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42 <H1 class="no-header">curs_bkgrnd 3x 2024-04-20 ncurses 6.4 Library calls</H1>
44 <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>
49 </PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
50 <STRONG>bkgrnd</STRONG>, <STRONG>wbkgrnd</STRONG>, <STRONG>bkgrndset</STRONG>, <STRONG>wbkgrndset</STRONG>, <STRONG>getbkgrnd</STRONG>, <STRONG>wgetbkgrnd</STRONG> -
51 manipulate background of a <EM>curses</EM> window of wide characters
54 </PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
55 <STRONG>#include</STRONG> <STRONG><curses.h></STRONG>
57 <STRONG>int</STRONG> <STRONG>bkgrnd(const</STRONG> <STRONG>cchar_t</STRONG> <STRONG>*</STRONG><EM>wch</EM><STRONG>);</STRONG>
58 <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>
60 <STRONG>void</STRONG> <STRONG>bkgrndset(const</STRONG> <STRONG>cchar_t</STRONG> <STRONG>*</STRONG><EM>wch</EM><STRONG>);</STRONG>
61 <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>
63 <STRONG>int</STRONG> <STRONG>getbkgrnd(cchar_t</STRONG> <STRONG>*</STRONG><EM>wch</EM><STRONG>);</STRONG>
64 <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>
67 </PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
68 The <EM>background</EM> of a <EM>curses</EM> window (in the library's "wide"
69 configuration) is a <EM>cchar</EM><STRONG>_</STRONG><EM>t</EM> combining a set of attributes (see
70 <STRONG><A HREF="curs_attr.3x.html">curs_attr(3x)</A></STRONG>) with a complex character called the <EM>blank</EM> <EM>character.</EM>
72 The blank character is a spacing character that populates a window's
73 character cells when their contents are erased without replacement.
74 The background's attributes are combined with all non-blank characters
75 written to the window, as with 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>
76 families of functions.
78 The blank character and attributes of the background combine with
79 characters written to the window as described below. The background
80 becomes a property of the character and moves with it through any
81 scrolling and insert/delete line/character operations.
83 To the extent possible on a given terminal, the attribute part of the
84 background is displayed as the graphic rendition of the character put
88 </PRE><H3><a name="h3-bkgrnd_wbkgrnd">bkgrnd, wbkgrnd</a></H3><PRE>
89 <STRONG>bkgrnd</STRONG> and <STRONG>wbkgrnd</STRONG> set the background property of <STRONG>stdscr</STRONG> or the
90 specified window and then apply this setting to every character cell in
93 <STRONG>o</STRONG> The rendition of every character in the window changes to the new
96 <STRONG>o</STRONG> Wherever the former background character appears, it changes to the
97 new background character.
99 <EM>ncurses</EM> updates the rendition of each character cell by comparing the
100 character, non-color attributes, and colors. The library applies to
101 following procedure to each cell in the window, whether or not it is
104 <STRONG>o</STRONG> <EM>ncurses</EM> first compares the cell's character to the previously
105 specified blank character; if they match, <EM>ncurses</EM> writes the new
106 blank character to the cell.
108 <STRONG>o</STRONG> <EM>ncurses</EM> then checks if the cell uses color, that is, its color pair
109 value is nonzero. If not, it simply replaces the attributes and
110 color pair in the cell with those from the new background
113 <STRONG>o</STRONG> If the cell uses color, and its background color matches that of
114 the current window background, <EM>ncurses</EM> removes attributes that may
115 have come from the current background and adds those from the new
116 background. It finishes by setting the cell's background to use
117 the new window background color.
119 <STRONG>o</STRONG> If the cell uses color, and its background color does not match
120 that of the current window background, <EM>ncurses</EM> updates only the
121 non-color attributes, first removing those that may have come from
122 the current background, and then adding attributes from the new
125 <EM>ncurses</EM> treats a background character value of zero (0) as a blank
128 If the terminal does not support color, or if color has not been
129 initialized with <STRONG><A HREF="curs_color.3x.html">start_color(3x)</A></STRONG>, <EM>ncurses</EM> ignores the new background
130 character's color attribute.
133 </PRE><H3><a name="h3-bkgrndset_wbkgrndset">bkgrndset, wbkgrndset</a></H3><PRE>
134 <STRONG>bkgrndset</STRONG> and <STRONG>wbkgrndset</STRONG> manipulate the background of the applicable
135 window, without updating the character cells as <STRONG>bkgrnd</STRONG> and <STRONG>wbkgrnd</STRONG> do;
136 only future writes reflect the updated background.
139 </PRE><H3><a name="h3-getbkgrnd_wgetbkgrnd">getbkgrnd, wgetbkgrnd</a></H3><PRE>
140 The <STRONG>getbkgrnd</STRONG> and <STRONG>wgetbkgrnd</STRONG> functions obtain the background character
141 and attribute pair of <STRONG>stdscr</STRONG> or the specified window and store it via
142 the <EM>wch</EM> pointer.
145 </PRE><H2><a name="h2-RETURN-VALUE">RETURN VALUE</a></H2><PRE>
146 <STRONG>bkgrndset</STRONG> and <STRONG>wbkgrndset</STRONG> do not return a value.
148 The other functions return <STRONG>ERR</STRONG> upon failure and <STRONG>OK</STRONG> upon success. In
149 <EM>ncurses</EM>, failure occurs if
151 <STRONG>o</STRONG> a <EM>WINDOW</EM> pointer <EM>win</EM> is null, or
153 <STRONG>o</STRONG> a <EM>cchar</EM><STRONG>_</STRONG><EM>t</EM> pointer <EM>wch</EM> is null.
156 </PRE><H2><a name="h2-NOTES">NOTES</a></H2><PRE>
157 <STRONG>bkgrnd</STRONG>, <STRONG>bkgrndset</STRONG>, and <STRONG>getbkgrnd</STRONG> may be implemented as macros.
159 Unlike their counterparts in the non-"wide" configuration of <EM>ncurses</EM>,
160 <STRONG>getbkgrnd</STRONG> and <STRONG>wgetbkgrnd</STRONG> supply the background character and attribute
161 in a modifiable <EM>cchar</EM><STRONG>_</STRONG><EM>t</EM> parameter, not as the return value.
164 </PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
165 X/Open Curses, Issue 4 describes these functions. It specifies no
166 error conditions for them.
168 X/Open Curses does not provide details of how the rendition is updated.
169 This implementation follows the approach used in SVr4 <EM>curses</EM>.
172 </PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
173 <STRONG><A HREF="curs_bkgd.3x.html">curs_bkgd(3x)</A></STRONG> describes the corresponding functions in the non-"wide"
174 configuration of <EM>ncurses</EM>.
176 <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>
180 ncurses 6.4 2024-04-20 <STRONG><A HREF="curs_bkgrnd.3x.html">curs_bkgrnd(3x)</A></STRONG>
184 <li><a href="#h2-NAME">NAME</a></li>
185 <li><a href="#h2-SYNOPSIS">SYNOPSIS</a></li>
186 <li><a href="#h2-DESCRIPTION">DESCRIPTION</a>
188 <li><a href="#h3-bkgrnd_wbkgrnd">bkgrnd, wbkgrnd</a></li>
189 <li><a href="#h3-bkgrndset_wbkgrndset">bkgrndset, wbkgrndset</a></li>
190 <li><a href="#h3-getbkgrnd_wgetbkgrnd">getbkgrnd, wgetbkgrnd</a></li>
193 <li><a href="#h2-RETURN-VALUE">RETURN VALUE</a></li>
194 <li><a href="#h2-NOTES">NOTES</a></li>
195 <li><a href="#h2-PORTABILITY">PORTABILITY</a></li>
196 <li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>