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curs_bkgd 3x

curs_bkgd(3x)                                                    curs_bkgd(3x)




NAME

       bkgdset,  wbkgdset,  bkgd,  wbkgd,  getbkgd  - curses window background
       manipulation routines


SYNOPSIS

       #include <curses.h>

       void bkgdset(chtype ch);
       void wbkgdset(WINDOW *win, chtype ch);

       int bkgd(chtype ch);
       int wbkgd(WINDOW *win, chtype ch);

       chtype getbkgd(WINDOW *win);


DESCRIPTION


bkgdset

       The bkgdset and wbkgdset routines  manipulate  the  background  of  the
       named  window.   The  window  background  is a chtype consisting of any
       combination 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  waddch.   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.

       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.


bkgd

       The bkgd and wbkgd functions set the background property of the current
       or  specified  window  and  then  apply this setting to every character
       position in that window.  According to  X/Open  Curses,  it  should  do
       this:

       o   The  rendition  of  every character on the screen is changed to the
           new background rendition.

       o   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  bkgd  or
       wbkgd 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:

       o   The  library  first  compares  the character, and if it matches the
           current character part of the background, it replaces that with the
           new background character.

       o   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.

       o   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.

       o   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, a space is assumed.

       If the terminal does not support  color,  or  if  color  has  not  been
       started   with   start_color,  the  new  background  character's  color
       attribute will be ignored.


getbkgd

       The getbkgd function returns  the  given  window's  current  background
       character/attribute pair.


RETURN VALUE

       These  functions are described in the XSI Curses standard, Issue 4.  It
       specifies that bkgd and wbkgd return  ERR  on  failure,  but  gives  no
       failure conditions.

       The  routines  bkgd and wbkgd return the integer OK, unless the library
       has not been initialized.

       In contrast, the SVr4.0 manual says bkgd and wbkgd may return OK "or  a
       non-negative  integer  if  immedok  is set", which refers to the return
       value from wrefresh (used to implement the immediate repainting).   The
       SVr4  curses  wrefresh  returns the number of characters written to the
       screen during the refresh.  This implementation does not do that.


NOTES

       Note that bkgdset and bkgd 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.


PORTABILITY

       These  functions  are  described  in  the  XSI Curses standard, Issue 4
       (X/Open Curses).


SEE ALSO

       curses(3x), curs_addch(3x), curs_attr(3x), curs_outopts(3x)



                                                                 curs_bkgd(3x)