bkgrnd, wbkgrnd, bkgrndset, wbkgrndset, getbkgrnd, wgetbkgrnd - manipulate background of a curses window

       Every curses window has a backgroundcharacter property: in the library's wide  configuration,  it  is  a
       curses complex character (cchar_t) that combines a set of attributes (and, if colors are enabled, a color
       pair  identifier)  with  a  character code.  When erasing (parts of) a window, curses replaces the erased
       cells with the background character.

       curses also uses the background character when writing characters to a populated window.

       •   The attribute part of the background character combines with all non-blank  character  cells  in  the
           window,  as  populated  by  the  wadd_wch(3NCURSES) and wins_wch(3NCURSES) families of functions (and
           those that call them).

       •   Both the character code and attributes of the background character combine with blank character cells
           in the window.

       The background character's set of attributes becomes a property of the character cell and  move  with  it
       through  any  scrolling  and  insert/delete  line/character  operations.   To  the extent possible on the
       terminal type, curses displays the attributes of the background character as the graphic rendition  of  a
       character cell on the display.

   bkgrnd,wbkgrndbkgrnd  and  wbkgrnd  set  the  background property of stdscr or the specified window and then apply this
       setting to every character cell in that window.

       •   The rendition of every character in the window changes to the new background rendition.

       •   Wherever the former background character appears, it changes to the new background character.

       ncurses updates the rendition of each character cell by comparing the  character,  non-color  attributes,
       and color pair selection.  The library applies to following procedure to each cell in the window, whether
       or not it is blank.

       •   ncurses first compares the cell's character to the previously specified background character; if they
           match, ncurses writes the new background character to the cell.

       •   ncurses  then  checks whether 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.

       •   If  the  cell  uses  color,  and  its background color matches that of the current window background,
           ncurses 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.

       •   If the cell uses color, and  its  background  color  does  not  match  that  of  the  current  window
           background,  ncurses  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.

       If the new background's character is non-spacing, ncurses reuses the old background character, except for
       one special case: ncurses treats a background character code of zero (0) as a space.

       If the terminal does not support color, or if color has not been initialized with  start_color(3NCURSES),
       ncurses ignores the new background character's color pair selection.

   bkgrndset,wbkgrndsetbkgrndset  and  wbkgrndset  manipulate  the  background  of  the  applicable window, without updating the
       character cells as bkgrnd and wbkgrnd do; only future writes reflect the updated background.

   getbkgrnd,wgetbkgrndgetbkgrnd and wgetbkgrnd respectively  obtain  stdscr's  or  the  given  window's  background  character,
       attributes, and color pair, and store it in their wch argument.

       X/Open Curses Issue 4 (1995) initially specified these functions.

bkgrnd,  wbkgrnd, bkgrndset, wbkgrndset, getbkgrnd, wgetbkgrnd - manipulate background of a curses window
       of wide characters

bkgrnd, bkgrndset, and getbkgrnd may be implemented as macros.

       Unlike  their  counterparts  in the non-wide configuration of ncurses, getbkgrnd and wgetbkgrnd store the
       background character in a modifiable cchar_t parameter, rather than supplying it as the return value.

       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.   ncurses  follows  the  approach
       used in SVr4 curses's non-wide functions for manipulating the window background.

bkgrndset and wbkgrndset do not return a value.

       Functions returning an int return ERR upon failure and OK upon success.  In ncurses, failure occurs if

       •   the curses screen has not been initialized,

       •   win is NULL, or

       •   wch is NULL.

bkgd(3NCURSES) describes the corresponding functions in the non-wide configuration of ncurses.

       ncurses(3NCURSES), add_wch(3NCURSES), attr(3NCURSES)

ncurses 6.5                                        2025-02-15                                   bkgrnd(3NCURSES)

#include<curses.h>intbkgrnd(constcchar_t*wch);intwbkgrnd(WINDOW*win,constcchar_t*wch);voidbkgrndset(constcchar_t*wch);voidwbkgrndset(WINDOW*win,constcchar_t*wch);intgetbkgrnd(cchar_t*wch);intwgetbkgrnd(WINDOW*win,cchar_t*wch);