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- * @Id: curs_bkgd.3x,v 1.25 2017/11/18 23:56:00 tom Exp @
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<H1 class="no-header">curs_bkgd 3x</H1>
<STRONG>void</STRONG> <STRONG>bkgdset(chtype</STRONG> <EM>ch</EM><STRONG>);</STRONG>
<STRONG>void</STRONG> <STRONG>wbkgdset(WINDOW</STRONG> <STRONG>*</STRONG><EM>win,</EM> <EM>chtype</EM> <EM>ch</EM><STRONG>);</STRONG>
+
<STRONG>int</STRONG> <STRONG>bkgd(chtype</STRONG> <EM>ch</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>wbkgd(WINDOW</STRONG> <STRONG>*</STRONG><EM>win</EM><STRONG>,</STRONG> <STRONG>chtype</STRONG> <EM>ch</EM><STRONG>);</STRONG>
+
<STRONG>chtype</STRONG> <STRONG>getbkgd(WINDOW</STRONG> <STRONG>*</STRONG><EM>win</EM><STRONG>);</STRONG>
</PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
</PRE><H3><a name="h3-bkgdset">bkgdset</a></H3><PRE>
- The <STRONG>bkgdset</STRONG> and <STRONG>wbkgdset</STRONG> routines manipulate the background of the
- named window. The window background is a <STRONG>chtype</STRONG> consisting of any com-
- bination of attributes (i.e., rendition) and a 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 character
- and moves with the character through any scrolling and insert/delete
- line/character operations.
+ The <STRONG>bkgdset</STRONG> and <STRONG>wbkgdset</STRONG> routines set the <EM>background</EM> for a window. A
+ window's background is a <STRONG>chtype</STRONG> consisting of any combination of
+ attributes (i.e., rendition) and a character:
+
+ <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>.
+
+ <STRONG>o</STRONG> Both the character and attribute parts of the background are
+ combined with blank characters that are written into the window.
+
+ The background becomes a property of each 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
</PRE><H3><a name="h3-bkgd">bkgd</a></H3><PRE>
The <STRONG>bkgd</STRONG> and <STRONG>wbkgd</STRONG> functions set the background property of the current
or specified window and then apply this setting to every character
- position in that window:
+ position in that window. According to X/Open Curses, it should do
+ this:
- <STRONG>o</STRONG> The rendition of every character on the screen is changed to the
+ <STRONG>o</STRONG> The rendition of every character on the screen is changed to the
new background rendition.
- <STRONG>o</STRONG> Wherever the former background character appears, it is changed to
+ <STRONG>o</STRONG> Wherever the former background character appears, it is changed to
the new background character.
+ Neither X/Open Curses nor the SVr4 manual pages give details about the
+ way the rendition of characters on the screen is updated when <STRONG>bkgd</STRONG> or
+ <STRONG>wbkgd</STRONG> is used to change the background character.
+
+ This implementation, like SVr4 curses, does not store the background
+ and window attribute contributions to each cell separately. It updates
+ the rendition by comparing the character, non-color attributes and
+ colors contained in the background. For each cell in the window,
+ whether or not it is blank:
+
+ <STRONG>o</STRONG> The library first compares the <EM>character</EM>, and if it matches the
+ current character part of the background, it replaces that with the
+ new background character.
+
+ When <STRONG>bkgdset</STRONG> is used to set the background character, that does not
+ update each cell in the window. A subsequent call to <STRONG>bkgd</STRONG> will
+ only modify the <EM>character</EM> in cells which match the current
+ background character.
+
+ <STRONG>o</STRONG> The library then checks if the cell uses color, i.e., 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 that matches the color in the current
+ background, the library removes attributes which may have come from
+ the current background and adds attributes from the new background.
+ It finishes by setting the cell to use the color from the new
+ background.
+
+ <STRONG>o</STRONG> If the cell uses color, and that does not match the color in the
+ current background, the library updates only the non-color
+ attributes, first removing those which may have come from the
+ current background, and then adding attributes from the new
+ background.
+
+ If the background's character value is zero (0), a space is assumed.
+
+ If the terminal does not support color, or if color has not been
+ started with <STRONG>start_color</STRONG>, the new background character's color
+ attribute will be ignored.
+
</PRE><H3><a name="h3-getbkgd">getbkgd</a></H3><PRE>
- The <STRONG>getbkgd</STRONG> function returns the given window's current background
+ The <STRONG>getbkgd</STRONG> function returns the given window's current background
character/attribute pair.
</PRE><H2><a name="h2-RETURN-VALUE">RETURN VALUE</a></H2><PRE>
- The routines <STRONG>bkgd</STRONG> and <STRONG>wbkgd</STRONG> return the integer <STRONG>OK</STRONG>. The SVr4.0 manual
- says "or a non-negative integer if <STRONG>immedok</STRONG> is set", but this appears to
- be an error.
+ These functions are described in the XSI Curses standard, Issue 4. It
+ specifies that <STRONG>bkgd</STRONG> and <STRONG>wbkgd</STRONG> return <STRONG>ERR</STRONG> on failure, but gives no
+ failure conditions.
+
+ The routines <STRONG>bkgd</STRONG> and <STRONG>wbkgd</STRONG> return the integer <STRONG>OK</STRONG>, unless the library
+ has not been initialized.
+
+ In contrast, the SVr4.0 manual says <STRONG>bkgd</STRONG> and <STRONG>wbkgd</STRONG> may return <STRONG>OK</STRONG> "or a
+ non-negative integer if <STRONG>immedok</STRONG> is set", which refers to the return
+ value from <STRONG>wrefresh</STRONG> (used to implement the immediate repainting). The
+ SVr4 curses <STRONG>wrefresh</STRONG> returns the number of characters written to the
+ screen during the refresh. This implementation does not do that.
</PRE><H2><a name="h2-NOTES">NOTES</a></H2><PRE>
Note that <STRONG>bkgdset</STRONG> and <STRONG>bkgd</STRONG> may be macros.
+ X/Open Curses mentions that the character part of the background must
+ be a single-byte value. This implementation, like SVr4, checks to
+ ensure that, and will reuse the old background character if the check
+ fails.
+
</PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
- These functions are described in the XSI Curses standard, Issue 4. It
- specifies that <STRONG>bkgd</STRONG> and <STRONG>wbkgd</STRONG> return <STRONG>ERR</STRONG> on failure, but gives no fail-
- ure conditions.
+ These functions are described in the XSI Curses standard, Issue 4
+ (X/Open Curses).
</PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
projects / ncurses.git / blobdiff