* sale, use or other dealings in this Software without prior written *
* authorization. *
****************************************************************************
- * @Id: curs_bkgrnd.3x,v 1.34 2023/12/02 21:30:00 tom Exp @
+ * @Id: curs_bkgrnd.3x,v 1.35 2023/12/16 23:00:21 tom Exp @
-->
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN">
<HTML>
<HEAD>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
<meta name="generator" content="Manpage converted by man2html - see https://invisible-island.net/scripts/readme.html#others_scripts">
-<TITLE>curs_bkgrnd 3x 2023-12-02 ncurses 6.4 Library calls</TITLE>
+<TITLE>curs_bkgrnd 3x 2023-12-16 ncurses 6.4 Library calls</TITLE>
<link rel="author" href="mailto:bug-ncurses@gnu.org">
</HEAD>
<BODY>
-<H1 class="no-header">curs_bkgrnd 3x 2023-12-02 ncurses 6.4 Library calls</H1>
+<H1 class="no-header">curs_bkgrnd 3x 2023-12-16 ncurses 6.4 Library calls</H1>
<PRE>
<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-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 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.
- <STRONG>o</STRONG> 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>.
+ 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.
- <STRONG>o</STRONG> Both the character and attribute parts of the background are
- combined with the blank characters.
+ 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.
- 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-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> The rendition of every character in the window changes to the new
+ background rendition.
-</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
- character position in that window:
+ <STRONG>o</STRONG> Wherever the former background character appears, it changes to the
+ new background character.
- <STRONG>o</STRONG> The rendition of every character on the screen is changed to the
- new background rendition.
+ <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> Wherever the former background character appears, it is changed to
- the new background character.
+ <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.
+ <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.
-</PRE><H3><a name="h3-getbkgrnd">getbkgrnd</a></H3><PRE>
- The <STRONG>getbkgrnd</STRONG> and <STRONG>wgetbkgrnd</STRONG> functions obtain the given or specified
- window's current background character and attribute pair and store it
- via the <EM>wch</EM> pointer.
+ <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.
+
+
+</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.
- Upon successful completion, the other functions return <STRONG>OK</STRONG>. Otherwise,
- they return <STRONG>ERR</STRONG>:
+ 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 null <EM>WINDOW</EM> pointer is treated as an error.
+ <STRONG>o</STRONG> a <EM>WINDOW</EM> pointer <EM>win</EM> is null, or
- <STRONG>o</STRONG> A null <EM>cchar</EM><STRONG>_</STRONG><EM>t</EM> pointer is treated as an error.
+ <STRONG>o</STRONG> a <EM>cchar</EM><STRONG>_</STRONG><EM>t</EM> pointer <EM>wch</EM> is null.
</PRE><H2><a name="h2-NOTES">NOTES</a></H2><PRE>
<STRONG>bkgrnd</STRONG>, <STRONG>bkgrndset</STRONG>, and <STRONG>getbkgrnd</STRONG> may be available as macros.
- 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>.
+ 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, 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>
-ncurses 6.4 2023-12-
02 <STRONG><A HREF="curs_bkgrnd.3x.html">curs_bkgrnd(3x)</A></STRONG>
+ncurses 6.4 2023-12-
16 <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-RETURN-VALUE">RETURN VALUE</a></li>
projects / ncurses.git / blobdiff