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| <H1 class="no-header">curs_bkgd 3x 2024-04-20 ncurses 6.5 Library calls</H1> |
| <PRE> |
| <STRONG><A HREF="curs_bkgd.3x.html">curs_bkgd(3x)</A></STRONG> Library calls <STRONG><A HREF="curs_bkgd.3x.html">curs_bkgd(3x)</A></STRONG> |
| |
| |
| |
| |
| </PRE><H2><a name="h2-NAME">NAME</a></H2><PRE> |
| <STRONG>bkgdset</STRONG>, <STRONG>wbkgdset</STRONG>, <STRONG>bkgd</STRONG>, <STRONG>wbkgd</STRONG>, <STRONG>getbkgd</STRONG> - manipulate background of a |
| <EM>curses</EM> window of characters |
| |
| |
| </PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE> |
| <STRONG>#include</STRONG> <STRONG><curses.h></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>void</STRONG> <STRONG>bkgdset(chtype</STRONG> <EM>ch</EM><STRONG>);</STRONG> |
| <STRONG>void</STRONG> <STRONG>wbkgdset(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> |
| The <EM>background</EM> of a <EM>curses</EM> window (in the library's non-"wide" |
| configuration) is a <EM>chtype</EM> combining a set of attributes (see |
| <STRONG><A HREF="curs_attr.3x.html">curs_attr(3x)</A></STRONG>) with a character called the <EM>blank</EM> <EM>character.</EM> |
| |
| 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_addch.3x.html">waddch(3x)</A></STRONG> and <STRONG><A HREF="curs_insch.3x.html">winsch(3x)</A></STRONG> families |
| of functions. |
| |
| 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-bkgd_wbkgd">bkgd, wbkgd</a></H3><PRE> |
| <STRONG>bkgd</STRONG> and <STRONG>wbkgd</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. |
| |
| <STRONG>o</STRONG> Wherever the former background character appears, it changes to the |
| new background character. |
| |
| <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. |
| |
| <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-bkgdset_wbkgdset">bkgdset, wbkgdset</a></H3><PRE> |
| <STRONG>bkgdset</STRONG> and <STRONG>wbkgdset</STRONG> manipulate the background of the applicable |
| window, without updating the character cells as <STRONG>bkgd</STRONG> and <STRONG>wbkgd</STRONG> do; only |
| future writes reflect the updated background. |
| |
| |
| </PRE><H3><a name="h3-getbkgd">getbkgd</a></H3><PRE> |
| <STRONG>getbkgd</STRONG> obtains the given window's background character and attribute |
| combination. |
| |
| |
| </PRE><H2><a name="h2-RETURN-VALUE">RETURN VALUE</a></H2><PRE> |
| Functions returning an <EM>int</EM> return <STRONG>OK</STRONG> on success. <STRONG>bkgd</STRONG> returns <STRONG>ERR</STRONG> if |
| the library has not been initialized. <STRONG>wbkgd</STRONG> and <STRONG>getbkgd</STRONG> return <STRONG>ERR</STRONG> if |
| a <EM>WINDOW</EM> pointer argument is null. |
| |
| <STRONG>bkgdset</STRONG> and <STRONG>wbkgdset</STRONG> do not return a value. |
| |
| <STRONG>getbkgd</STRONG> returns a window's background character and attribute |
| combination. |
| |
| |
| </PRE><H2><a name="h2-NOTES">NOTES</a></H2><PRE> |
| Unusually, there is no <STRONG>wgetbkgd</STRONG> function; <STRONG>getbkgd</STRONG> behaves as one would |
| expect <STRONG>wgetbkgd</STRONG> to, accepting a <EM>WINDOW</EM> pointer argument. |
| |
| <STRONG>bkgd</STRONG> and <STRONG>bkgdset</STRONG> may be implemented as macros. |
| |
| X/Open Curses mentions that the character part of the background must |
| be a single-byte value. <EM>ncurses</EM>, like SVr4 <EM>curses</EM>, 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> |
| X/Open Curses, Issue 4 describes these functions. It specifies that |
| <STRONG>bkgd</STRONG>, <STRONG>wbkgd</STRONG>, and <STRONG>getbkgd</STRONG> return <STRONG>ERR</STRONG> on failure (in the case of the |
| last, this value is cast to <EM>chtype</EM>), but describes no failure |
| conditions. |
| |
| The SVr4.0 manual says that <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><A HREF="curs_refresh.3x.html">wrefresh(3x)</A></STRONG>, used to implement the immediate repainting. SVr4 |
| <EM>curses</EM>'s <STRONG>wrefresh</STRONG> returns the number of characters written to the |
| screen during the refresh. <EM>ncurses</EM> does not do that. |
| |
| Neither X/Open Curses nor the SVr4 manual pages detail how the |
| rendition of characters on the screen updates when <STRONG>bkgd</STRONG> or <STRONG>wbkgd</STRONG> |
| changes the background character. <EM>ncurses</EM>, like SVr4 <EM>curses</EM>, does not |
| (in its non-"wide" configuration) store the background and window |
| attribute contributions to each character cell separately. |
| |
| |
| </PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE> |
| <STRONG><A HREF="curs_bkgrnd.3x.html">curs_bkgrnd(3x)</A></STRONG> describes the corresponding functions in the "wide" |
| configuration of <EM>ncurses</EM>. |
| |
| <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> |
| |
| |
| |
| ncurses 6.5 2024-04-20 <STRONG><A HREF="curs_bkgd.3x.html">curs_bkgd(3x)</A></STRONG> |
| </PRE> |
| <div class="nav"> |
| <ul> |
| <li><a href="#h2-NAME">NAME</a></li> |
| <li><a href="#h2-SYNOPSIS">SYNOPSIS</a></li> |
| <li><a href="#h2-DESCRIPTION">DESCRIPTION</a> |
| <ul> |
| <li><a href="#h3-bkgd_wbkgd">bkgd, wbkgd</a></li> |
| <li><a href="#h3-bkgdset_wbkgdset">bkgdset, wbkgdset</a></li> |
| <li><a href="#h3-getbkgd">getbkgd</a></li> |
| </ul> |
| </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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