.\"***************************************************************************
-.\" Copyright 2018-2022,2023 Thomas E. Dickey *
+.\" Copyright 2018-2023,2024 Thomas E. Dickey *
.\" Copyright 2002-2016,2017 Free Software Foundation, Inc. *
.\" *
.\" Permission is hereby granted, free of charge, to any person obtaining a *
.\" authorization. *
.\"***************************************************************************
.\"
-.\" $Id: curs_get_wch.3x,v 1.26 2023/10/07 21:19:07 tom Exp $
-.TH curs_get_wch 3X 2023-10-07 "ncurses 6.4" "Library calls"
+.\" $Id: curs_get_wch.3x,v 1.40 2024/04/20 19:23:03 tom Exp $
+.TH curs_get_wch 3X 2024-04-20 "ncurses @NCURSES_MAJOR@.@NCURSES_MINOR@" "Library calls"
.ie \n(.g \{\
.ds `` \(lq
.ds '' \(rq
\fBint mvget_wch(int \fIy\fP, int \fIx\fP, wint_t *\fIwch\fP);
\fBint mvwget_wch(WINDOW *\fIwin\fP, int \fIy\fP, int \fIx\fP, wint_t *\fIwch\fP);
.PP
-\fBint unget_wch(const wchar_t \fIwch\fP);
+\fBint unget_wch(const wchar_t \fIwc\fP);
.fi
.SH DESCRIPTION
-.SS wget_wch
-The
-\fBget_wch\fP,
-\fBwget_wch\fP,
-\fBmvget_wch\fP, and
-\fBmvwget_wch\fP
-functions read a character
-from the terminal associated with the current or specified window.
-In no-delay mode,
-if no input is waiting, the value \fBERR\fP is returned.
-In delay mode,
-the program waits until the system passes text through to the program.
-Depending on the setting of \fBcbreak\fP,
-this is after one character (cbreak mode),
-or after the first newline (nocbreak mode).
-In half-delay mode,
-the program waits until the user types a character or the specified
-timeout interval has elapsed.
+.SS "Reading Characters"
+.B \%wget_wch
+gathers a key stroke
+.I wch
+from the terminal keyboard associated with a
+.I curses
+window
+.IR win ,
+returning
+.B OK
+if a wide character is read,
+.B \%KEY_CODE_YES
+if a function key is read,
+and
+.B ERR
+if no key event is available.
+\fB\%ncurses\fP(3X) describes the variants of this function.
.PP
-Unless \fBnoecho\fP has been set,
-these routines echo the character into the designated window.
+When input is pending,
+.B \%wget_wch
+stores an integer
+identifying the key stroke in
+.IR 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 often results in a distinct code.
+The behavior of other keys depends on whether
+.I win
+is in keypad mode;
+see subsections \*(``Keypad Mode\*('' and \*(``Predefined Key Codes\*(''
+in \fB\%getch\fP(3X).
.PP
-If the window is not a pad and has been moved or modified since the
-last call to \fBwrefresh\fP,
-\fBwrefresh\fP will be called before another character is read.
+If no input is pending,
+then if the no-delay flag is set in the window
+(see \fB\%nodelay\fP(3X)),
+the function returns
+.BR ERR ;
+otherwise,
+.I curses
+waits until the terminal has input.
+If \fB\%cbreak\fP(3X)
+has been called,
+this happens after one character is read.
+If \fB\%nocbreak\fP(3X)
+has been called,
+it occurs when the next newline is read.
+If \fB\%halfdelay\fP(3X)
+has been called,
+.I curses
+waits until a character is typed or the specified delay elapses.
.PP
-If \fBkeypad\fP is enabled,
-these functions respond to
-the pressing of a function key by setting the object pointed to by
-\fIwch\fP
-to the keycode assigned to the function key,
-and returning \fBKEY_CODE_YES\fP.
-If a character (such as escape) that could be the
-beginning of a function key is received, curses sets a timer.
-If the remainder
-of the sequence does arrive within the designated time, curses passes through
-the character; otherwise, curses returns the function key value.
-For this
-reason, many terminals experience a delay between the time a user presses
-the escape key and the time the escape is returned to the program.
+If \fB\%echo\fP(3X) has been called,
+and the window is not a pad,
+.I curses
+writes
+.I wch
+to the window
+(at the cursor position)
+per the following rules.
+.bP
+If
+.I wch
+matches the terminal's erase character,
+the cursor moves leftward one position
+and the new position is erased
+as if \fB\%wmove\fP(3X) and then \fB\%wdelch\fP(3X) were called.
+When the window's keypad mode is enabled
+(see below),
+.B \%KEY_LEFT
+and
+.B \%KEY_BACKSPACE
+are handled the same way.
+.bP
+.I curses
+writes any other
+.I wch
+to the window,
+as with \fB\%wecho_wchar\fP(3X).
+.bP
+If the window has been moved or modified since the last call to
+\fB\%wrefresh\fP(3X),
+.I curses
+calls
+.BR \%wrefresh .
.PP
-The keycodes returned by these functions are the same as those
-returned by \fBwgetch\fP:
+If
+.I wch
+is a carriage return and \fBnl\fP(3X) has been called,
+.B \%wgetch
+stores the the character code for newline
+(line feed)
+in
+.I wch
+instead.
+.SS "Ungetting Characters"
+.B \%unget_wch
+places
+.I wch
+into the input queue to be returned by the next call to
+.BR \%wget_wch .
+A single input queue serves all windows.
+.SH RETURN VALUE
+.B \%wget_wch
+returns
+.B OK
+when it reads a wide character and
+.B \%KEY_CODE_YES
+when it reads a function key code.
+It returns
+.B ERR
+if
+.bP
+the
+.I \%WINDOW
+pointer is
+.BR NULL ,
+or
.bP
-The predefined function
-keys are listed in \fB<curses.h>\fP as macros with values outside the range
-of 8-bit characters.
-Their names begin with \fBKEY_\fP.
+its timeout expires without any data arriving,
+or
.bP
-Other (user-defined) function keys
-which may be defined using \fBdefine_key\fP(3X) have no names,
-but also are expected to have values outside the range of 8-bit characters.
-.SS unget_wch
-The
-\fBunget_wch\fP
-function pushes the wide character
-\fIwch\fP
-back onto the head of the input queue, so the wide character
-is returned by the next call to
-\fBget_wch\fP.
-The pushback of
-one character is guaranteed.
-If the program calls
-\fBunget_wch\fP
-too many times without an intervening call to
-\fBget_wch\fP,
-the operation may fail.
+execution was interrupted by a signal,
+in which case
+.B \%errno
+is set to
+.BR \%EINTR .
.PP
-Unlike \fBungetch\fP and \fBwgetch\fP,
-\fBunget_wch\fP cannot distinguish special characters
-returned by \fBwget_wch\fP from ordinary characters.
-An application can push special keys
-which it may read via \fBwget_wch\fP
-by checking for the \fBKEY_CODE_YES\fP result,
-and using \fBungetch\fP for those special keys.
+Functions prefixed with \*(``mv\*('' first perform cursor movement and
+fail if the position
+.RI ( y ,
+.IR x )
+is outside the window boundaries.
+.PP
+.B \%unget_wch
+returns
+.B OK
+on success and
+.B ERR
+if there is no more room in the input queue.
.SH NOTES
-The header file
-\fB<curses.h>\fP
-automatically
-includes the header file
-\fB<stdio.h>\fP.
+See the \*(``NOTES\*('' section of \fB\%wgetch\fP(3X).
.PP
-Applications should not define the escape key by itself as a single-character
-function.
+All of these functions except
+.B \%wget_wch
+and
+.B \%unget_wch
+may be implemented as macros.
.PP
-When using
-\fBget_wch\fP,
-\fBwget_wch\fP,
-\fBmvget_wch\fP, or
-\fBmvwget_wch\fP, applications should
-not use
-\fBnocbreak\fP
-mode and
-\fBecho\fP
-mode
-at the same time.
-Depending on the state of the tty driver when each character
-is typed, the program may produce undesirable results.
+Unlike \fB\%wgetch\fP(3X),
+.B \%wget_wch
+and its variants store the value of the input character in an additional
+.I wch
+parameter instead of the return value.
.PP
-All functions except \fBwget_wch\fP and \fBunget_wch\fP
-may be macros.
-.SH RETURN VALUE
-When
-\fBget_wch\fP,
-\fBwget_wch\fP,
-\fBmvget_wch\fP, and
-\fBmvwget_wch\fP
-functions successfully
-report the pressing of a function key, they return
-\fBKEY_CODE_YES\fP.
-When they successfully report a wide character, they return
-\fBOK\fP.
-Otherwise, they return
-\fBERR\fP.
+Unlike
+.BR \%ungetch ,
+.B \%unget_wch
+cannot distinguish function key codes
+.B \%wget_wch
+from conventional character codes.
+An application can overcome this limitation by pushing function key
+codes with
+.B \%ungetch
+and subsequently checking the return value of
+.B \%wget_wch
+for a match with
+.BR \%KEY_CODE_YES .
+.SH EXTENSIONS
+See the \*(``EXTENSIONS\*('' section of \fB\%wgetch\fP(3X).
+.SH PORTABILITY
+Applications employing
+.I \%ncurses
+extensions should condition their use on the visibility of the
+.B \%NCURSES_VERSION
+preprocessor macro.
.PP
-Upon successful completion,
-\fBunget_wch\fP
-returns
-\fBOK\fP.
-Otherwise, the function returns
-\fBERR\fP.
+X/Open Curses,
+Issue 4 describes these functions.
+It specifies no error conditions for them.
.PP
-Functions with a \*(``mv\*('' prefix first perform a cursor movement using
-\fBwmove\fP, and return an error if the position is outside the window,
-or if the window pointer is null.
+See the \*(``PORTABILITY\*('' section of \fB\%wgetch\fP(3X) regarding
+the interaction of
+.B \%wget_wch
+with signal handlers.
.SH SEE ALSO
+\fB\%curs_getch\fP(3X) describes comparable functions of the
+.I \%ncurses
+library in its non-wide-character configuration.
+.PP
\fB\%curses\fP(3X),
-\fB\%curs_getch\fP(3X),
-\fB\%curs_ins_wch\fP(3X),
+\fB\%curs_add_wch\fP(3X),
\fB\%curs_inopts\fP(3X),
\fB\%curs_move\fP(3X),
\fB\%curs_refresh\fP(3X)
projects / ncurses.git / blobdiff