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  37 <TITLE>curs_bkgrnd 3x 2024-03-23 ncurses 6.4 Library calls</TITLE>
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  42 <H1 class="no-header">curs_bkgrnd 3x 2024-03-23 ncurses 6.4 Library calls</H1>
  43 <PRE>
  44 <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>
  45
  46
  47
  48
  49 </PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
  50        <STRONG>bkgrnd</STRONG>,   <STRONG>wbkgrnd</STRONG>,   <STRONG>bkgrndset</STRONG>,  <STRONG>wbkgrndset</STRONG>,  <STRONG>getbkgrnd</STRONG>,  <STRONG>wgetbkgrnd</STRONG>  -
  51        manipulate background of a <EM>curses</EM> window of wide characters
  52
  53
  54 </PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
  55        <STRONG>#include</STRONG> <STRONG>&lt;curses.h&gt;</STRONG>
  56
  57        <STRONG>int</STRONG> <STRONG>bkgrnd(const</STRONG> <STRONG>cchar_t</STRONG> <STRONG>*</STRONG><EM>wch</EM><STRONG>);</STRONG>
  58        <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>
  59
  60        <STRONG>void</STRONG> <STRONG>bkgrndset(const</STRONG> <STRONG>cchar_t</STRONG> <STRONG>*</STRONG><EM>wch</EM><STRONG>);</STRONG>
  61        <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>
  62
  63        <STRONG>int</STRONG> <STRONG>getbkgrnd(cchar_t</STRONG> <STRONG>*</STRONG><EM>wch</EM><STRONG>);</STRONG>
  64        <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>
  65
  66
  67 </PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
  68        The  <EM>background</EM>  of  a  <EM>curses</EM>  window   (in   the   library's   "wide"
  69        configuration)  is  a  <EM>cchar</EM><STRONG>_</STRONG><EM>t</EM>  combining  a  set  of  attributes  (see
  70        <STRONG><A HREF="curs_attr.3x.html">curs_attr(3x)</A></STRONG>) with a complex character called the <EM>blank</EM> <EM>character.</EM>
  71
  72        The blank character is a spacing character that  populates  a  window's
  73        character  cells  when  their  contents are erased without replacement.
  74        The background's attributes are combined with all non-blank  characters
  75        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>
  76        families of functions.
  77
  78        The blank character and  attributes  of  the  background  combine  with
  79        characters  written  to  the window as described below.  The background
  80        becomes a property of the character  and  moves  with  it  through  any
  81        scrolling and insert/delete line/character operations.
  82
  83        To  the  extent possible on a given terminal, the attribute part of the
  84        background is displayed as the graphic rendition of the  character  put
  85        on the screen.
  86
  87
  88 </PRE><H3><a name="h3-bkgrnd_wbkgrnd">bkgrnd, wbkgrnd</a></H3><PRE>
  89        <STRONG>bkgrnd</STRONG>  and  <STRONG>wbkgrnd</STRONG>  set  the  background  property  of  <STRONG>stdscr</STRONG> or the
  90        specified window and then apply this setting to every character cell in
  91        that window.
  92
  93        <STRONG>o</STRONG>   The  rendition  of every character in the window changes to the new
  94            background rendition.
  95
  96        <STRONG>o</STRONG>   Wherever the former background character appears, it changes to the
  97            new background character.
  98
  99        <EM>ncurses</EM>  updates  the rendition of each character cell by comparing the
 100        character, non-color attributes, and colors.  The  library  applies  to
 101        following  procedure  to  each cell in the window, whether or not it is
 102        blank.
 103
 104        <STRONG>o</STRONG>   <EM>ncurses</EM> first compares  the  cell's  character  to  the  previously
 105            specified  blank  character;  if they match, <EM>ncurses</EM> writes the new
 106            blank character to the cell.
 107
 108        <STRONG>o</STRONG>   <EM>ncurses</EM> then checks if the cell uses color, that is, its color pair
 109            value  is  nonzero.   If not, it simply replaces the attributes and
 110            color  pair  in  the  cell  with  those  from  the  new  background
 111            character.
 112
 113        <STRONG>o</STRONG>   If  the  cell  uses color, and its background color matches that of
 114            the current window background, <EM>ncurses</EM> removes attributes that  may
 115            have  come  from the current background and adds those from the new
 116            background.  It finishes by setting the cell's  background  to  use
 117            the new window background color.
 118
 119        <STRONG>o</STRONG>   If  the  cell  uses  color, and its background color does not match
 120            that of the current window background,  <EM>ncurses</EM>  updates  only  the
 121            non-color  attributes, first removing those that may have come from
 122            the current background, and then adding  attributes  from  the  new
 123            background.
 124
 125        <EM>ncurses</EM>  treats  a  background  character  value of zero (0) as a blank
 126        character.
 127
 128        If the terminal does not support  color,  or  if  color  has  not  been
 129        initialized  with  <STRONG><A HREF="curs_color.3x.html">start_color(3x)</A></STRONG>,  <EM>ncurses</EM> ignores the new background
 130        character's color attribute.
 131
 132
 133 </PRE><H3><a name="h3-bkgrndset_wbkgrndset">bkgrndset, wbkgrndset</a></H3><PRE>
 134        <STRONG>bkgrndset</STRONG> and <STRONG>wbkgrndset</STRONG> manipulate the background  of  the  applicable
 135        window,  without updating the character cells as <STRONG>bkgrnd</STRONG> and <STRONG>wbkgrnd</STRONG> do;
 136        only future writes reflect the updated background.
 137
 138
 139 </PRE><H3><a name="h3-getbkgrnd_wgetbkgrnd">getbkgrnd, wgetbkgrnd</a></H3><PRE>
 140        The <STRONG>getbkgrnd</STRONG> and <STRONG>wgetbkgrnd</STRONG> functions obtain the background  character
 141        and  attribute  pair of <STRONG>stdscr</STRONG> or the specified window and store it via
 142        the <EM>wch</EM> pointer.
 143
 144
 145 </PRE><H2><a name="h2-RETURN-VALUE">RETURN VALUE</a></H2><PRE>
 146        <STRONG>bkgrndset</STRONG> and <STRONG>wbkgrndset</STRONG> do not return a value.
 147
 148        The other functions return <STRONG>ERR</STRONG> upon failure and <STRONG>OK</STRONG>  upon  success.   In
 149        <EM>ncurses</EM>, failure occurs if
 150
 151        <STRONG>o</STRONG>   a <EM>WINDOW</EM> pointer <EM>win</EM> is null, or
 152
 153        <STRONG>o</STRONG>   a <EM>cchar</EM><STRONG>_</STRONG><EM>t</EM> pointer <EM>wch</EM> is null.
 154
 155
 156 </PRE><H2><a name="h2-NOTES">NOTES</a></H2><PRE>
 157        <STRONG>bkgrnd</STRONG>, <STRONG>bkgrndset</STRONG>, and <STRONG>getbkgrnd</STRONG> may be implemented as macros.
 158
 159        Unlike  their  counterparts in the non-"wide" configuration of <EM>ncurses</EM>,
 160        <STRONG>getbkgrnd</STRONG> and <STRONG>wgetbkgrnd</STRONG> supply the background character and  attribute
 161        in a modifiable <EM>cchar</EM><STRONG>_</STRONG><EM>t</EM> parameter, not as the return value.
 162
 163
 164 </PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
 165        X/Open  Curses,  Issue  4,  describes these functions.  It specifies no
 166        error conditions for them.
 167
 168        X/Open Curses does not provide details of how the rendition is updated.
 169        This implementation follows the approach used in SVr4 <EM>curses</EM>.
 170
 171
 172 </PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
 173        <STRONG><A HREF="curs_bkgd.3x.html">curs_bkgd(3x)</A></STRONG>  describes  the corresponding functions in the non-"wide"
 174        configuration of <EM>ncurses</EM>.
 175
 176        <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>
 177
 178
 179
 180 ncurses 6.4                       2024-03-23                   <STRONG><A HREF="curs_bkgrnd.3x.html">curs_bkgrnd(3x)</A></STRONG>
 181 </PRE>
 182 <div class="nav">
 183 <ul>
 184 <li><a href="#h2-NAME">NAME</a></li>
 185 <li><a href="#h2-SYNOPSIS">SYNOPSIS</a></li>
 186 <li><a href="#h2-DESCRIPTION">DESCRIPTION</a>
 187 <ul>
 188 <li><a href="#h3-bkgrnd_wbkgrnd">bkgrnd, wbkgrnd</a></li>
 189 <li><a href="#h3-bkgrndset_wbkgrndset">bkgrndset, wbkgrndset</a></li>
 190 <li><a href="#h3-getbkgrnd_wgetbkgrnd">getbkgrnd, wgetbkgrnd</a></li>
 191 </ul>
 192 </li>
 193 <li><a href="#h2-RETURN-VALUE">RETURN VALUE</a></li>
 194 <li><a href="#h2-NOTES">NOTES</a></li>
 195 <li><a href="#h2-PORTABILITY">PORTABILITY</a></li>
 196 <li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>
 197 </ul>
 198 </div>
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