anchor.diff:        (setcchar ptr wch 0 0 (cffi:null-pointer))
   
         ;; TODO 200404 works with ncurses 6.1 but not with 6.2
  -      ;; manually replacing line 209: SetChar2(*cp, CharOf(new_char));
  +      ;; manually replacing line 209 in lib_bkgd.c
  +      ;; SetChar2(*cp, CharOf(new_char));
         ;; with: win->_line[y].text[x] = win->_nc_bkgd;
         ;; from ncurses 6.1 is an ugly, but working solution for wbkgrnd
         ;; in ncurses-6.2-20200404/ncurses/base/lib_bkgd.c.
  +      ;; fixed since ncurses-6.2-20210206, will be released as ncurses 6.3.
         (wbkgrnd scr ptr)
  +
  +      ;; adding a single cchar_t
  +      (wadd-wch scr ptr)
         
         (wrefresh scr)
         (wgetch scr)
  
positive.code: ;; Use the cchar_t type for setcchar.
  ;; cchar-chars is a pointer to an integer array here, like the C prototype requires.
  (defun ut04 ()
    (let ((scr (initscr)))
      (start-color)
      ;; Initialize color pair 1, yellow 3 on red 1.
  
negative.code: ;; 126 works 7bit
  ;; 161 doesn't work 8bit
  ;; #x2592 doesn't work wide char
  
  ;; https://c-for-dummies.com/blog/?p=2568
  
  (defun ut05 (&optional (n #x2592))
    "Minimal example of creating a cchar_t and setting it as a window background.
  
  Also see t02b."
  
    ;; call setlocale explicitly because it is not called any more by SBCL
    ;; sbcl-2.0.3/src/runtime/runtime.c
    (setlocale +LC-ALL+ "")
  
    (let ((scr (initscr)))
  