'\" t
.\"***************************************************************************
-.\" Copyright (c) 1998-2014,2015 Free Software Foundation, Inc. *
+.\" Copyright (c) 1998-2017,2018 Free Software Foundation, Inc. *
.\" *
.\" Permission is hereby granted, free of charge, to any person obtaining a *
.\" copy of this software and associated documentation files (the *
.\" authorization. *
.\"***************************************************************************
.\"
-.\" $Id: curs_getch.3x,v 1.42 2015/07/21 08:44:04 tom Exp $
+.\" $Id: curs_getch.3x,v 1.53 2018/07/28 22:15:59 tom Exp $
.TH curs_getch 3X ""
.na
.hy 0
.de bP
-.IP \(bu 4
+.ie n .IP \(bu 4
+.el .IP \(bu 2
..
.SH NAME
\fBgetch\fR,
.SS Keypad mode
.PP
If \fBkeypad\fR is \fBTRUE\fR, and a function key is pressed, the token for
-that function key is returned instead of the raw characters.
-Possible function
-keys are defined in \fB<curses.h>\fR as macros with values outside the range
-of 8-bit characters whose names begin with \fBKEY_\fR.
+that function key is returned instead of the raw characters:
+.bP
+The predefined function
+keys are listed in \fB<curses.h>\fR as macros with values outside the range
+of 8-bit characters.
+Their names begin with \fBKEY_\fR.
+.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.
+.PP
Thus, a variable
intended to hold the return value of a function key must be of short size or
larger.
otherwise, the function key value is returned.
For this reason, many terminals experience a delay between the time
a user presses the escape key and the escape is returned to the program.
+.PP
+In \fBncurses\fP, the timer normally expires after
+the value in \fBESCDELAY\fP (see \fBcurs_variables\fP(3X)).
+If \fBnotimeout\fP is \fBTRUE\fP, the timer does not expire;
+it is an infinite (or very large) value.
+Because function keys usually begin with an escape character,
+the terminal may appear to hang in notimeout mode after pressing the escape key
+until another key is pressed.
.SS Ungetting characters
.PP
The \fBungetch\fR routine places \fIch\fR back onto the input queue to be
There is just one input queue for all windows.
.PP
.SS Predefined key-codes
-The following special keys, defined in \fB<curses.h>\fR, may be returned by
-\fBgetch\fR if \fBkeypad\fR has been enabled.
+The following special keys are defined in \fB<curses.h>\fR.
+.bP
+Except for the special case \fBKEY_RESIZE\fP,
+it is necessary to enable \fBkeypad\fR for \fBgetch\fP to return these codes.
+.bP
Not all of these are necessarily supported on any particular terminal.
+.bP
+The naming convention may seem obscure, with some apparent
+misspellings (such as "RSUME" for "resume").
+The names correspond to the long terminfo capability names for the keys,
+and were defined long ago, in the 1980s.
.PP
.TS
center tab(/) ;
.B KEY_RESIZE
is returned when the \fBSIGWINCH\fP signal has been detected
(see \fBinitscr\fP(3X) and \fBresizeterm\fR(3X)).
+This code is returned whether or not \fBkeypad\fP has been enabled.
.bP
.B KEY_MOUSE
is returned for mouse-events (see \fBcurs_mouse\fR(3X)).
+This code relies upon whether or not \fBkeypad\fP(3X) has been enabled,
+because (e.g., with \fIxterm\fP mouse prototocol) ncurses must
+read escape sequences,
+just like a function key.
.SS Testing key-codes
.PP
The \fBhas_key\fR routine takes a key-code value from the above list, and
.PP
.SH RETURN VALUE
All routines return the integer \fBERR\fR upon failure and an integer value
-other than \fBERR\fR (\fBOK\fR in the case of ungetch()) upon successful
+other than \fBERR\fR (\fBOK\fR in the case of \fBungetch\fP) upon successful
completion.
.RS 3
.TP 5
\fBungetch\fP
-returns ERR
+returns \fBERR\fP
if there is no more room in the FIFO.
.TP
\fBwgetch\fP
-returns ERR
+returns \fBERR\fP
if the window pointer is null, or
-if its timeout expires without having any data.
+if its timeout expires without having any data, or
+if the execution was interrupted by a signal (\fBerrno\fR will be set to
+\fBEINTR\fR).
.RE
.PP
Functions with a "mv" prefix first perform a cursor movement using
keypad code looks for a following function-key sequence.
.PP
Some keys may be the same as commonly used control
-keys, e.g., \fBKEY_ENTER\fP versus control/M, \fBKEY_BACKSPACE\fP versus control/H.
+keys, e.g.,
+\fBKEY_ENTER\fP versus control/M,
+\fBKEY_BACKSPACE\fP versus control/H.
Some curses implementations may differ according to whether they
treat these control keys specially (and ignore the terminfo), or
use the terminfo definitions.
progress or not, and also (in some implementations) depending on whether an
input timeout or non-blocking mode has been set.
.PP
+\fBKEY_MOUSE\fP is mentioned in XSI Curses, along with a few related
+terminfo capabilities, but no higher-level functions use the feature.
+The implementation in ncurses is an extension.
+.PP
+\fBKEY_RESIZE\fP is an extension first implemented for ncurses.
+NetBSD curses later added this extension.
+.PP
Programmers concerned about portability should be prepared for either of two
cases: (a) signal receipt does not interrupt \fBgetch\fR; (b) signal receipt
-interrupts \fBgetch\fR and causes it to return ERR with \fBerrno\fR set to
+interrupts \fBgetch\fR and causes it to return \fBERR\fP with \fBerrno\fR set to
\fBEINTR\fR.
-Under the \fBncurses\fR implementation, handled signals never
-interrupt \fBgetch\fR.
.PP
The \fBhas_key\fR function is unique to \fBncurses\fR.
We recommend that
\fBcurs_mouse\fR(3X),
\fBcurs_move\fR(3X),
\fBcurs_refresh\fR(3X),
+\fBcurs_variables\fR(3X),
\fBresizeterm\fR(3X).
.PP
Comparable functions in the wide-character (ncursesw) library are
projects / ncurses.git / blobdiff