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+ * Copyright 2018-2023,2024 Thomas E. Dickey *
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- * @Id: curs_bkgrnd.3x,v 1.10 2018/12/09 00:50:50 tom Exp @
+ * @Id: curs_bkgrnd.3x,v 1.40 2024/03/23 19:59:45 tom Exp @
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-<H1 class="no-header">curs_bkgrnd 3x</H1>
+<H1 class="no-header">curs_bkgrnd 3x 2024-03-23 ncurses 6.4 Library calls</H1>
<PRE>
-<STRONG><A HREF="curs_bkgrnd.3x.html">curs_bkgrnd(3x)</A></STRONG>
<STRONG><A HREF="curs_bkgrnd.3x.html">curs_bkgrnd(3x)</A></STRONG>
+<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> - <STRONG>curses</STRONG>
- window complex background manipulation routines
+ <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(</STRONG> <STRONG>const</STRONG> <STRONG>cchar_t</STRONG> <STRONG>*</STRONG><EM>wch</EM><STRONG>);</STRONG>
- <STRONG>int</STRONG> <STRONG>wbkgrnd(</STRONG> <STRONG>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>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>
+ The <EM>background</EM> of a <EM>curses</EM> window (in the library's "wide"
+ configuration) is a <EM>cchar</EM><STRONG>_</STRONG><EM>t</EM> combining a set of attributes (see
+ <STRONG><A HREF="curs_attr.3x.html">curs_attr(3x)</A></STRONG>) with a complex character called the <EM>blank</EM> <EM>character.</EM>
-</PRE><H3><a name="h3-bkgrndset">bkgrndset</a></H3><PRE>
- The <STRONG>bkgrndset</STRONG> and <STRONG>wbkgrndset</STRONG> routines manipulate the background of the
- named window. The window background is a <STRONG>cchar_t</STRONG> consisting of any
- combination of attributes (i.e., rendition) and a complex 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 charac-
- ter and moves with the character through any scrolling and
- insert/delete line/character operations.
+ The blank character is a spacing character that populates a window's
+ character cells when their contents are erased without replacement.
+ The background's attributes are combined with all non-blank characters
+ 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>
+ families of functions.
- 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.
+ The blank character and attributes of the background combine with
+ characters written to the window as described below. The background
+ becomes a property of the character and moves with it through any
+ scrolling and insert/delete line/character operations.
+ To the extent possible on a given 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-bkgrnd">bkgrnd</a></H3><PRE>
- The <STRONG>bkgrnd</STRONG> and <STRONG>wbkgrnd</STRONG> functions set the background property of the
- current or specified window and then apply this setting to every char-
- acter position in that window:
- <STRONG>o</STRONG> The rendition of every character on the screen is changed to the
- new background rendition.
+</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> Wherever the former background character appears, it is changed to
- the new background character.
+ <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.
-</PRE><H3><a name="h3-getbkgrnd">getbkgrnd</a></H3><PRE>
- The <STRONG>getbkgrnd</STRONG> function returns the given window's current background
- character/attribute pair via the <STRONG>wch</STRONG> pointer. If the given window
- pointer is null, the character is not updated (but no error returned).
+ <EM>ncurses</EM> updates the rendition of each character cell by comparing the
+ character, non-color attributes, and colors. 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 blank character; if they match, <EM>ncurses</EM> writes the new
+ blank character to the cell.
-</PRE><H2><a name="h2-NOTES">NOTES</a></H2><PRE>
- Note that <STRONG>bkgrnd</STRONG>, <STRONG>bkgrndset</STRONG>, and <STRONG>getbkgrnd</STRONG> may be macros.
+ <STRONG>o</STRONG> <EM>ncurses</EM> then checks if 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.
+
+ <EM>ncurses</EM> treats a background character value of zero (0) as a blank
+ character.
+
+ 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 attribute.
+
+
+</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.
- X/Open Curses does not provide details on how the rendition is changed.
- This implementation follows the approach used in SVr4 curses, which is
- explained in the manual page for <STRONG>wbkgd</STRONG>.
+
+</PRE><H3><a name="h3-getbkgrnd_wgetbkgrnd">getbkgrnd, wgetbkgrnd</a></H3><PRE>
+ The <STRONG>getbkgrnd</STRONG> and <STRONG>wgetbkgrnd</STRONG> functions obtain the background character
+ and attribute pair of <STRONG>stdscr</STRONG> or the specified window and store it via
+ the <EM>wch</EM> pointer.
</PRE><H2><a name="h2-RETURN-VALUE">RETURN VALUE</a></H2><PRE>
- The <STRONG>bkgrndset</STRONG> and <STRONG>wbkgrndset</STRONG> routines do not return a value.
+ <STRONG>bkgrndset</STRONG> and <STRONG>wbkgrndset</STRONG> do not return a value.
+
+ The other functions return <STRONG>ERR</STRONG> upon failure and <STRONG>OK</STRONG> upon success. In
+ <EM>ncurses</EM>, failure occurs if
+
+ <STRONG>o</STRONG> a <EM>WINDOW</EM> pointer <EM>win</EM> is null, or
- Upon successful completion, the other functions return <STRONG>OK</STRONG>. Otherwise,
- they return <STRONG>ERR</STRONG>:
+ <STRONG>o</STRONG> a <EM>cchar</EM><STRONG>_</STRONG><EM>t</EM> pointer <EM>wch</EM> is null.
- <STRONG>o</STRONG> A null window pointer is treated as an error.
- <STRONG>o</STRONG> A null character pointer is treated as an error.
+</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" configuration of <EM>ncurses</EM>,
+ <STRONG>getbkgrnd</STRONG> and <STRONG>wgetbkgrnd</STRONG> supply the background character and attribute
+ in a modifiable <EM>cchar</EM><STRONG>_</STRONG><EM>t</EM> parameter, not as the return value.
</PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
- These functions are described in the XSI Curses standard, Issue 4
- (X/Open Curses).
+ 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.
+ This implementation follows the approach used in SVr4 <EM>curses</EM>.
</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_bkgd.3x.html">curs_bkgd(3x)</A></STRONG>
+ <STRONG><A HREF="curs_bkgd.3x.html">curs_bkgd(3x)</A></STRONG> describes the corresponding functions in the non-"wide"
+ 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>
-
<STRONG><A HREF="curs_bkgrnd.3x.html">curs_bkgrnd(3x)</A></STRONG>
+
ncurses 6.4 2024-03-23 <STRONG><A HREF="curs_bkgrnd.3x.html">curs_bkgrnd(3x)</A></STRONG>
</PRE>
<div class="nav">
<ul>
<li><a href="#h2-SYNOPSIS">SYNOPSIS</a></li>
<li><a href="#h2-DESCRIPTION">DESCRIPTION</a>
<ul>
-<li><a href="#h3-bkgrndset">bkgrndset</a></li>
-<li><a href="#h3-bkgrnd">bkgrnd</a></li>
-<li><a href="#h3-getbkgrnd">getbkgrnd</a></li>
+<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-NOTES">NOTES</a></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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