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30 * @Id: curs_bkgd.3x,v 1.34 2022/02/12 20:06:41 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 manipulate the background of the
70 named window. The window background is a <STRONG>chtype</STRONG> consisting of any
71 combination of attributes (i.e., rendition) and a character. The
72 attribute part of the background is combined (OR'ed) with all non-blank
73 characters that are written into the window with <STRONG>waddch</STRONG>. Both the
74 character and attribute parts of the background are combined with the
75 blank characters. The background becomes a property of the character
76 and moves with the character through any scrolling and insert/delete
77 line/character operations.
79 To the extent possible on a particular terminal, the attribute part of
80 the background is displayed as the graphic rendition of the character
84 </PRE><H3><a name="h3-bkgd">bkgd</a></H3><PRE>
85 The <STRONG>bkgd</STRONG> and <STRONG>wbkgd</STRONG> functions set the background property of the current
86 or specified window and then apply this setting to every character
87 position in that window. According to X/Open Curses, it should do
90 <STRONG>o</STRONG> The rendition of every character on the screen is changed to the
91 new background rendition.
93 <STRONG>o</STRONG> Wherever the former background character appears, it is changed to
94 the new background character.
96 Neither X/Open Curses nor the SVr4 manual pages give details about the
97 way the rendition of characters on the screen is updated when <STRONG>bkgd</STRONG> or
98 <STRONG>wbkgd</STRONG> is used to change the background character.
100 This implementation, like SVr4 curses, does not store the background
101 and window attribute contributions to each cell separately. It updates
102 the rendition by comparing the character, non-color attributes and
103 colors contained in the background. For each cell in the window,
104 whether or not it is blank:
106 <STRONG>o</STRONG> The library first compares the <EM>character</EM>, and if it matches the
107 current character part of the background, it replaces that with the
108 new background character.
110 <STRONG>o</STRONG> The library then checks if the cell uses color, i.e., its color
111 pair value is nonzero. If not, it simply replaces the attributes
112 and color pair in the cell with those from the new background
115 <STRONG>o</STRONG> If the cell uses color, and that matches the color in the current
116 background, the library removes attributes which may have come from
117 the current background and adds attributes from the new background.
118 It finishes by setting the cell to use the color from the new
121 <STRONG>o</STRONG> If the cell uses color, and that does not match the color in the
122 current background, the library updates only the non-color
123 attributes, first removing those which may have come from the
124 current background, and then adding attributes from the new
127 If the background's character value is zero, a space is assumed.
129 If the terminal does not support color, or if color has not been
130 started with <STRONG>start_color</STRONG>, the new background character's color
131 attribute will be ignored.
134 </PRE><H3><a name="h3-getbkgd">getbkgd</a></H3><PRE>
135 The <STRONG>getbkgd</STRONG> function returns the given window's current background
136 character/attribute pair.
139 </PRE><H2><a name="h2-RETURN-VALUE">RETURN VALUE</a></H2><PRE>
140 These functions are described in the XSI Curses standard, Issue 4. It
141 specifies that <STRONG>bkgd</STRONG> and <STRONG>wbkgd</STRONG> return <STRONG>ERR</STRONG> on failure, but gives no
144 The routines <STRONG>bkgd</STRONG> and <STRONG>wbkgd</STRONG> return the integer <STRONG>OK</STRONG>, unless the library
145 has not been initialized.
147 In contrast, the SVr4.0 manual says <STRONG>bkgd</STRONG> and <STRONG>wbkgd</STRONG> may return <STRONG>OK</STRONG> "or a
148 non-negative integer if <STRONG>immedok</STRONG> is set", which refers to the return
149 value from <STRONG>wrefresh</STRONG> (used to implement the immediate repainting). The
150 SVr4 curses <STRONG>wrefresh</STRONG> returns the number of characters written to the
151 screen during the refresh. This implementation does not do that.
154 </PRE><H2><a name="h2-NOTES">NOTES</a></H2><PRE>
155 Note that <STRONG>bkgdset</STRONG> and <STRONG>bkgd</STRONG> may be macros.
157 X/Open Curses mentions that the character part of the background must
158 be a single-byte value. This implementation, like SVr4, checks to
159 ensure that, and will reuse the old background character if the check
163 </PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
164 These functions are described in the XSI Curses standard, Issue 4
168 </PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
169 <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>
173 <STRONG><A HREF="curs_bkgd.3x.html">curs_bkgd(3x)</A></STRONG>
177 <li><a href="#h2-NAME">NAME</a></li>
178 <li><a href="#h2-SYNOPSIS">SYNOPSIS</a></li>
179 <li><a href="#h2-DESCRIPTION">DESCRIPTION</a>
181 <li><a href="#h3-bkgdset">bkgdset</a></li>
182 <li><a href="#h3-bkgd">bkgd</a></li>
183 <li><a href="#h3-getbkgd">getbkgd</a></li>
186 <li><a href="#h2-RETURN-VALUE">RETURN VALUE</a></li>
187 <li><a href="#h2-NOTES">NOTES</a></li>
188 <li><a href="#h2-PORTABILITY">PORTABILITY</a></li>
189 <li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>