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curs_get_wch 3x 2025-01-18 ncurses 6.5 Library calls

curs_get_wch(3x)                 Library calls                curs_get_wch(3x)




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(3x) 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(3x).

       If  no input is pending, then if the no-delay flag is set in the window
       (see nodelay(3x)), the function returns ERR;  otherwise,  curses  waits
       until  the  terminal  has  input.   If  cbreak(3x)  or raw(3x) has been
       called, this happens after one character is read.  If  nocbreak(3x)  or
       noraw(3x)  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(3x) has been called, curses waits until input  is
       available or the specified delay elapses.

       If echo(3x) 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.

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

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

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

       If  the wide character is a carriage return and nl(3x) has been called,
       wget_wch stores the 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

       o   its timeout expires without any data arriving, or

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

       Functions taking a WINDOW pointer argument fail if the pointer is NULL.

       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(3x).

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

       Unlike wgetch(3x), 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(3x).


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(3x) regarding the interaction
       of wget_wch with signal handlers.


HISTORY

       These functions were  initially  specified  by  X/Open  Curses  Issue 4
       (1995).   The  System V Interface Definition Version 4 of the same year
       specified  functions  named  wgetwch  (with  the  usual  variants)  and
       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

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

       curses(3x),     curs_add_wch(3x),    curs_inopts(3x),    curs_move(3x),
       curs_refresh(3x)



ncurses 6.5                       2025-01-18                  curs_get_wch(3x)