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30 * @Id: curs_bkgd.3x,v 1.35 2022/06/25 21:55:45 tom Exp @
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37 <TITLE>curs_bkgd 3x</TITLE>
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42 <H1 class="no-header">curs_bkgd 3x</H1>
44 <STRONG><A HREF="curs_bkgd.3x.html">curs_bkgd(3x)</A></STRONG> <STRONG><A HREF="curs_bkgd.3x.html">curs_bkgd(3x)</A></STRONG>
49 </PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
50 <STRONG>bkgdset</STRONG>, <STRONG>wbkgdset</STRONG>, <STRONG>bkgd</STRONG>, <STRONG>wbkgd</STRONG>, <STRONG>getbkgd</STRONG> - <STRONG>curses</STRONG> window background
54 </PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
55 <STRONG>#include</STRONG> <STRONG><curses.h></STRONG>
57 <STRONG>void</STRONG> <STRONG>bkgdset(chtype</STRONG> <EM>ch</EM><STRONG>);</STRONG>
58 <STRONG>void</STRONG> <STRONG>wbkgdset(WINDOW</STRONG> <STRONG>*</STRONG><EM>win,</EM> <EM>chtype</EM> <EM>ch</EM><STRONG>);</STRONG>
60 <STRONG>int</STRONG> <STRONG>bkgd(chtype</STRONG> <EM>ch</EM><STRONG>);</STRONG>
61 <STRONG>int</STRONG> <STRONG>wbkgd(WINDOW</STRONG> <STRONG>*</STRONG><EM>win</EM><STRONG>,</STRONG> <STRONG>chtype</STRONG> <EM>ch</EM><STRONG>);</STRONG>
63 <STRONG>chtype</STRONG> <STRONG>getbkgd(WINDOW</STRONG> <STRONG>*</STRONG><EM>win</EM><STRONG>);</STRONG>
66 </PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
68 </PRE><H3><a name="h3-bkgdset">bkgdset</a></H3><PRE>
69 The <STRONG>bkgdset</STRONG> and <STRONG>wbkgdset</STRONG> routines set the <EM>background</EM> for a window. A
70 window's background is a <STRONG>chtype</STRONG> consisting of any combination of
71 attributes (i.e., rendition) and a character:
73 <STRONG>o</STRONG> The attribute part of the background is combined (OR'ed) with all
74 non-blank characters that are written into the window with <STRONG>waddch</STRONG>.
76 <STRONG>o</STRONG> Both the character and attribute parts of the background are
77 combined with blank characters that are written into the window.
79 The background becomes a property of each character and moves with the
80 character through any scrolling and insert/delete line/character
83 To the extent possible on a particular terminal, the attribute part of
84 the background is displayed as the graphic rendition of the character
88 </PRE><H3><a name="h3-bkgd">bkgd</a></H3><PRE>
89 The <STRONG>bkgd</STRONG> and <STRONG>wbkgd</STRONG> functions set the background property of the current
90 or specified window and then apply this setting to every character
91 position in that window. According to X/Open Curses, it should do
94 <STRONG>o</STRONG> The rendition of every character on the screen is changed to the
95 new background rendition.
97 <STRONG>o</STRONG> Wherever the former background character appears, it is changed to
98 the new background character.
100 Neither X/Open Curses nor the SVr4 manual pages give details about the
101 way the rendition of characters on the screen is updated when <STRONG>bkgd</STRONG> or
102 <STRONG>wbkgd</STRONG> is used to change the background character.
104 This implementation, like SVr4 curses, does not store the background
105 and window attribute contributions to each cell separately. It updates
106 the rendition by comparing the character, non-color attributes and
107 colors contained in the background. For each cell in the window,
108 whether or not it is blank:
110 <STRONG>o</STRONG> The library first compares the <EM>character</EM>, and if it matches the
111 current character part of the background, it replaces that with the
112 new background character.
114 When <STRONG>bkgdset</STRONG> is used to set the background character, that does not
115 update each cell in the window. A subsequent call to <STRONG>bkgd</STRONG> will
116 only modify the <EM>character</EM> in cells which match the current
117 background character.
119 <STRONG>o</STRONG> The library then checks if the cell uses color, i.e., its color
120 pair value is nonzero. If not, it simply replaces the attributes
121 and color pair in the cell with those from the new background
124 <STRONG>o</STRONG> If the cell uses color, and that matches the color in the current
125 background, the library removes attributes which may have come from
126 the current background and adds attributes from the new background.
127 It finishes by setting the cell to use the color from the new
130 <STRONG>o</STRONG> If the cell uses color, and that does not match the color in the
131 current background, the library updates only the non-color
132 attributes, first removing those which may have come from the
133 current background, and then adding attributes from the new
136 If the background's character value is zero (0), a space is assumed.
138 If the terminal does not support color, or if color has not been
139 started with <STRONG>start_color</STRONG>, the new background character's color
140 attribute will be ignored.
143 </PRE><H3><a name="h3-getbkgd">getbkgd</a></H3><PRE>
144 The <STRONG>getbkgd</STRONG> function returns the given window's current background
145 character/attribute pair.
148 </PRE><H2><a name="h2-RETURN-VALUE">RETURN VALUE</a></H2><PRE>
149 These functions are described in the XSI Curses standard, Issue 4. It
150 specifies that <STRONG>bkgd</STRONG> and <STRONG>wbkgd</STRONG> return <STRONG>ERR</STRONG> on failure, but gives no
153 The routines <STRONG>bkgd</STRONG> and <STRONG>wbkgd</STRONG> return the integer <STRONG>OK</STRONG>, unless the library
154 has not been initialized.
156 In contrast, the SVr4.0 manual says <STRONG>bkgd</STRONG> and <STRONG>wbkgd</STRONG> may return <STRONG>OK</STRONG> "or a
157 non-negative integer if <STRONG>immedok</STRONG> is set", which refers to the return
158 value from <STRONG>wrefresh</STRONG> (used to implement the immediate repainting). The
159 SVr4 curses <STRONG>wrefresh</STRONG> returns the number of characters written to the
160 screen during the refresh. This implementation does not do that.
163 </PRE><H2><a name="h2-NOTES">NOTES</a></H2><PRE>
164 Note that <STRONG>bkgdset</STRONG> and <STRONG>bkgd</STRONG> may be macros.
166 X/Open Curses mentions that the character part of the background must
167 be a single-byte value. This implementation, like SVr4, checks to
168 ensure that, and will reuse the old background character if the check
172 </PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
173 These functions are described in the XSI Curses standard, Issue 4
177 </PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
178 <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>
182 <STRONG><A HREF="curs_bkgd.3x.html">curs_bkgd(3x)</A></STRONG>
186 <li><a href="#h2-NAME">NAME</a></li>
187 <li><a href="#h2-SYNOPSIS">SYNOPSIS</a></li>
188 <li><a href="#h2-DESCRIPTION">DESCRIPTION</a>
190 <li><a href="#h3-bkgdset">bkgdset</a></li>
191 <li><a href="#h3-bkgd">bkgd</a></li>
192 <li><a href="#h3-getbkgd">getbkgd</a></li>
195 <li><a href="#h2-RETURN-VALUE">RETURN VALUE</a></li>
196 <li><a href="#h2-NOTES">NOTES</a></li>
197 <li><a href="#h2-PORTABILITY">PORTABILITY</a></li>
198 <li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>