NAME

       get_wch,  wget_wch,  mvget_wch,  mvwget_wch,  unget_wch - get (or push back) a wide character from curses
       terminal keyboard buffer

SYNOPSIS

       #include <curses.h>

       int get_wch(wint_t * wch);
       int wget_wch(WINDOW * win, wint_t * wch);
       int mvget_wch(int y, int x, wint_t * wch);
       int mvwget_wch(WINDOW * win, int y, int x, wint_t * wch);

       int unget_wch(const wchar_t wc);

DESCRIPTION

   Reading Characters
       wget_wch gathers a key event from the terminal keyboard associated with a curses window win, returning OK
       if a wide character is read, KEY_CODE_YES if a function  key  is  read,  and  ERR  if  no  key  event  is
       available.  ncurses(3NCURSES) describes the variants of this function.

       When  input is pending, wget_wch stores an integer identifying the key event in wch; for alphanumeric and
       punctuation keys, this value corresponds to the character encoding used by  the  terminal.   Use  of  the
       control  key as a modifier, by holding it down while pressing and releasing another key, often results in
       a distinct code.  The behavior of other keys depends on whether win is in keypad  mode;  see  subsections
       “Keypad Mode” and “Predefined Key Codes” in getch(3NCURSES).

       If  no  input  is  pending,  then  if the no-delay flag is set in the window (see nodelay(3NCURSES)), the
       function returns ERR; otherwise, curses waits until the  terminal  has  input.   If  cbreak(3NCURSES)  or
       raw(3NCURSES)  has  been  called,  this  happens  after  one character is read.  If nocbreak(3NCURSES) or
       noraw(3NCURSES) has been called, it occurs when the  next  newline  is  read.   (Because  the  terminal's
       canonical  or  “cooked” mode is line-buffered, multiple wget_wch calls may then be necessary to empty the
       input queue.)  If halfdelay(3NCURSES) has been called, curses waits  until  input  is  available  or  the
       specified delay elapses.

       If echo(3NCURSES) has been called, and the window is not a pad, curses writes the wide character from the
       input queue to the window (at the cursor position) per the following rules.

       •   If  the  wide character matches the terminal's erase character (see erasewchar(3NCURSES)), the cursor
           moves leftward one  position  and  the  new  position  is  erased  as  if  wmove(3NCURSES)  and  then
           wdelch(3NCURSES)  were  called.   When  the window's keypad mode is enabled (see below), KEY_LEFT and
           KEY_BACKSPACE are handled the same way.

       •   curses writes any other wide character to the window, as with wecho_wchar(3NCURSES).

       •   If the window win has been moved or modified since the last call to wrefresh(3NCURSES), curses  calls
           wrefresh on it.

       If  the  wide  character  is a carriage return and nl(3NCURSES) has been called, wget_wch stores the wide
       character code for line feed in wch instead.

   Ungetting Characters
       unget_wch places wc into the input queue to be retrieved by the next call to wget_wch.   A  single  input
       queue serves all windows associated with the screen.

RETURN VALUE

       wget_wch  returns  OK when it reads a wide character, KEY_CODE_YES when it reads a function key code, and
       ERR on failure.  wget_wch fails if

       •   its timeout expires without any data arriving, or

       •   execution was interrupted by a signal, in which case errno is set to EINTR.

       Functions taking a WINDOW pointer argument fail if win is a null pointer.

       Functions prefixed with “mv” first perform cursor movement and fail if the position (y, x) is outside the
       window boundaries.

       unget_wch returns OK on success and ERR if there is no more room in the input queue.

NOTES

       See the “NOTES” section of wgetch(3NCURSES).

       All of these functions except wget_wch and unget_wch may be implemented as macros.

       Unlike wgetch(3NCURSES), wget_wch and its  variants  store  the  value  of  the  input  character  in  an
       additional wch parameter instead of the return value.

       Unlike  ungetch,  unget_wch  cannot distinguish function key codes from conventional character codes.  An
       application can overcome this limitation by pushing function key  codes  with  ungetch  and  subsequently
       checking the return value of wget_wch for a match with KEY_CODE_YES.

EXTENSIONS

       See the “EXTENSIONS” section of wgetch(3NCURSES).

PORTABILITY

       Applications  employing  ncurses  extensions  should  condition  their  use  on  the  visibility  of  the
       NCURSES_VERSION preprocessor macro.

       X/Open Curses Issue 4 describes these functions.  It specifies no error conditions for them.

       See the “PORTABILITY” section of wgetch(3NCURSES) regarding  the  interaction  of  wget_wch  with  signal
       handlers.

HISTORY

       X/Open  Curses  Issue 4  (1995)  initially  specified these functions.  The System V Interface Definition
       Version 4 of the same year specified functions named wgetwch (with its variants)  ungetwch.   These  were
       later  additions  to  SVr4.x,  not  appearing  in the first SVr4 (1989).  They differ from X/Open's later
       wget_wch and unget_wch in that wgetwch takes no wch argument, but returns the (wide) key code as  an  int
       (with  no  provision  for distinguishing a character code from a function key code); and ungetwch takes a
       non-const int argument.

SEE ALSO

       getch(3NCURSES)  describes  comparable  functions  of  the  ncurses  library  in  its  non-wide-character
       configuration.

       ncurses(3NCURSES), add_wch(3NCURSES), inopts(3NCURSES), move(3NCURSES), refresh(3NCURSES)

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