.\"	$NetBSD: curses_input.3,v 1.30 2022/05/21 12:34:44 uwe Exp $
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.\" Copyright (c) 2002
.\"	Brett Lymn (blymn@NetBSD.org, brett_lymn@yahoo.com.au)
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.Dd May 16, 2022
.Dt CURSES_INPUT 3
.Os
.Sh NAME
.Nm curses_input ,
.Nm getch ,
.Nm wgetch ,
.Nm mvgetch ,
.Nm mvwgetch ,
.Nm define_key ,
.Nm keyok ,
.Nm has_key ,
.Nm getnstr ,
.Nm wgetnstr ,
.Nm mvgetnstr ,
.Nm mvwgetnstr ,
.Nm getstr ,
.Nm wgetstr ,
.Nm mvgetstr ,
.Nm mvwgetstr ,
.Nm keypad ,
.Nm is_keypad ,
.Nm notimeout ,
.Nm timeout ,
.Nm wtimeout ,
.Nm nodelay ,
.Nm ungetch ,
.Nm set_escdelay
.Nd curses input stream routines
.Sh LIBRARY
.Lb libcurses
.Sh SYNOPSIS
.In curses.h
.Ft int
.Fn getch "void"
.Ft int
.Fn wgetch "WINDOW *win"
.Ft int
.Fn mvgetch "int y" "int x"
.Ft int
.Fn mvwgetch "WINDOW *win" "int y" "int x"
.Ft int
.Fn keyok "int key_symbol" "bool flag"
.Ft int
.Fn has_key "int key_symbol"
.Ft int
.Fn define_key "char *sequence" "int key_symbol"
.Ft int
.Fn getnstr "char *str" "int limit"
.Ft int
.Fn wgetnstr "WINDOW *win" "char *str" "int limit"
.Ft int
.Fn mvgetnstr "int y" "int x" "char *str" "int limit"
.Ft int
.Fn mvwgetnstr "WINDOW *win" "int y" "int x" "char *str" "int limit"
.Ft int
.Fn getstr "char *str"
.Ft int
.Fn wgetstr "WINDOW *win" "char *str"
.Ft int
.Fn mvgetstr "int y" "int x" "char *str"
.Ft int
.Fn mvwgetstr "WINDOW *win" "int y" "int x" "char *str"
.Ft int
.Fn keypad "WINDOW *win" "bool flag"
.Ft bool
.Fn is_keypad "const WINDOW *win"
.Ft int
.Fn notimeout "WINDOW *win" "bool flag"
.Ft void
.Fn timeout "int delay"
.Ft void
.Fn wtimeout "WINDOW *win" "int delay"
.Ft int
.Fn nodelay "WINDOW *win" "bool flag"
.Ft int
.Fn ungetch "int c"
.Ft int
.Fn set_escdelay "int escdelay"
.Pp
.Va extern int ESCDELAY ;
.Sh DESCRIPTION
These functions read characters and strings from the window input file
descriptor.
.Pp
The
.Fn getch
function reads a character from the
.Dv stdscr
input file descriptor and returns it.
If the
.Fn keypad
flag has been set to
.Dv TRUE ,
then
.Fn getch
will assemble multi-character key sequences into key symbols,
If the terminal is resized,
.Fn getch
will return
.Dv KEY_RESIZE ,
regardless of the setting of
.Fn keypad .
Calling
.Fn getch
will cause an implicit
.Fn refresh
on
.Dv stdscr .
.Pp
The
.Fn wgetch
function is the same as the
.Fn getch
function, excepting that it reads from the input file descriptor associated
with the window specified by
.Fa win .
.Pp
If the
.Fn keypad
flag is
.Dv TRUE
then the assembly of specific key symbols can be disabled by using the
.Fn keyok
function.
If the
.Fa flag
is set to
.Dv FALSE
on a key symbol then
.Fn getch
will behave as if the character sequence associated with that key symbol
was not recognised and will return the component characters one at a time to
the caller.
The
.Fn is_keypad
function returns
.Dv TRUE
if the
.Fn
keypad
flag is set for the window specified by
.Fa win .
.Pp
The
.Fn has_key
function takes a key value and returns
.Dv TRUE
if the current terminal recognises a key with that value, otherwise
.Dv FALSE .
.Pp
Custom associations between sequences of characters and a key symbol can
be made by using the
.Fn define_key
function.
Normally, these associations are made by the information in the
.Xr terminfo 5
database but the
.Fn define_key
function gives the capability to remove or add more associations.
If
.Fn define_key
is passed a non-NULL string in
.Fa sequence
it will associate that sequence with the key symbol passed in
.Fa key_symbol .
The key symbol may be one of the ones listed below or a custom value that
is application defined.
It is valid to have multiple character sequences map to the same key
symbol and there are no constraints on the length of the sequence allowed.
The assembly of custom sequences follow the same rules for inter-character
timing and so forth as the
.Xr terminfo 5
derived ones.
If
.Fn define_key
is passed a NULL in
.Fa sequence
then all associations for the key symbol in
.Fa key_symbol
will be deleted, this includes any associations that were derived from
.Xr terminfo 5 .
.Pp
The
.Fn mvgetch
and
.Fn mvwgetch
functions are the same as the
.Fn getch
and
.Fn wgetch
functions, respectively, excepting that
.Fn wmove
is called to move the cursor to the position specified by
.Fa y ,
.Fa x
before the character is read.
.Pp
Calling
.Fn getnstr ,
.Fn wgetnstr ,
.Fn mvgetnstr
or
.Fn mvwgetnstr
is effectively the same as calling
.Fn getch
repeatedly until a newline is received or the character limit
.Fa limit
is reached.
Once this happens the string is
.Dv NULL
terminated and returned in
.Fa str .
During input, the normal curses input key processing is performed and
affects the input buffer.
The
.Fn mvgetnstr
function calls
.Fn wmove
to move the cursor to the position given by
.Fa y ,
.Fa x
before getting the string,
.Fn wgetnstr
reads the input from the designated window,
.Fn mvwgetnstr
moves the cursor to the position given by
.Fa y ,
.Fa x
before getting the input from the designated window.
.Pp
The functions
.Fn getstr ,
.Fn wgetstr ,
.Fn mvgetstr ,
and
.Fn mvwgetstr
are similar to
.Fn getnstr ,
.Fn wgetnstr ,
.Fn mvgetnstr ,
and
.Fn mvwgetnstr ,
respectively, excepting that there is no limit on the number of characters
that may be inserted into
.Fa str .
This may cause the buffer to be overflowed, so their use is not recommended.
.Pp
The
.Fn keypad
function is used to affect how
.Fn getch
processes input characters.
If
.Fa flag
is set to
.Dv TRUE ,
then
.Fn getch
will scan the input stream looking for multi-character key sequences
that are emitted by some terminal function keys.
If a recognised sequence of characters is found, then
.Fn getch
will collapse that sequence into an integer key symbol, as shown below.
The default setting for the flag is
.Dv FALSE .
.Pp
The
.Fn notimeout
function controls whether or not
.Fn getch
will wait indefinitely between characters in a multi-character key
sequence or not.
If
.Fa flag
is
.Dv TRUE ,
then there is no timeout applied between characters comprising a
multi-character key sequence.
If
.Fa flag
is
.Dv FALSE ,
then the component characters of a multi-character sequence must not
have an inter-character gap of more than
.Va ESCDELAY .
If this timing is exceeded, then the multi-character key assembly is
deemed to have failed and the characters read thus far are returned
one at a time when
.Fn getch
is called.
The default setting for the flag is
.Dv FALSE .
The default value of
.Va ESCDELAY
is 300ms.
If
.Va ESCDELAY
is negative, no timeout is applied between characters comprising a
multi-character key sequence.
.Pp
The
.Fn timeout
function affects the behaviour of
.Fn getch
when reading a character from
.Dv stdscr .
If
.Fa delay
is negative, then
.Fn getch
will block indefinitely on a read.
If
.Fa delay
is 0, then
.Fn getch
will return immediately with
.Dv ERR
if there are no characters immediately available.
If
.Fa delay
is a positive number, then
.Fn getch
will wait for that many milliseconds before returning and, if no character
was available, then
.Dv ERR
will be returned.
Note that for a positive number, the timeout is only accurate to the nearest
tenth of a second.
Also, the maximum value of
.Fa delay
is 25500 milliseconds.
The
.Fn wtimeout
function does the same as
.Fn timeout
but applies to the specified window
.Fa win .
.Pp
The
.Fn nodelay
function turns on and off blocking reads for
.Fn getch .
If
.Fa flag
is
.Dv TRUE ,
then
.Fn getch
will not block on reads, if
.Fa flag
is
.Dv FALSE ,
then reads will block.
The default setting for the flag is
.Dv FALSE .
.Fn nodelay win TRUE
is equivalent to
.Fn wtimeout win 0
and
.Fn nodelay win FALSE
is equivalent to
.Fn wtimeout win \-1 .
.Pp
.Fn ungetch
will convert
.Fa c
into an unsigned char and push that character back onto the input stream.
Only one character of push-back is guaranteed to work, more may be possible
depending on system resources.
.Pp
The
.Fn set_escdelay
function sets the
.Va ESCDELAY
value of the current screen to
.Fa escdelay .
.Sh RETURN VALUES
The functions
.Fn getch ,
.Fn wgetch ,
.Fn mvgetch ,
and
.Fn mvwgetch
will return the value of the key pressed or
.Dv ERR
in the case of an error or a timeout.
Additionally, if
.Fn keypad TRUE
has been called on a window, then it may return one of the following values:
.Pp
.Bl -column "Termcap entry" "getch Return Value" "Key Function" -offset indent
.It Sy "Termcap entry" Ta Sy "getch Return Value" Ta Sy "Key Function"
.It \&!1 Ta KEY_SSAVE Ta Shift Save
.It \&!2 Ta KEY_SSUSPEND Ta Shift Suspend
.It \&!3 Ta KEY_SUNDO Ta Shift Undo
.It \&#1 Ta KEY_SHELP Ta Shift Help
.It \&#2 Ta KEY_SHOME Ta Shift Home
.It \&#3 Ta KEY_SIC Ta Shift Insert Character
.It \&#4 Ta KEY_SLEFT Ta Shift Left Arrow
.It \&%0 Ta KEY_REDO Ta Redo
.It \&%1 Ta KEY_HELP Ta Help
.It \&%2 Ta KEY_MARK Ta Mark
.It \&%3 Ta KEY_MESSAGE Ta Message
.It \&%4 Ta KEY_MOVE Ta Move
.It \&%5 Ta KEY_NEXT Ta Next Object
.It \&%6 Ta KEY_OPEN Ta Open
.It \&%7 Ta KEY_OPTIONS Ta Options
.It \&%8 Ta KEY_PREVIOUS Ta Previous Object
.It \&%9 Ta KEY_PRINT Ta Print
.It \&%a Ta KEY_SMESSAGE Ta Shift Message
.It \&%b Ta KEY_SMOVE Ta Shift Move
.It \&%c Ta KEY_SNEXT Ta Shift Next Object
.It \&%d Ta KEY_SOPTIONS Ta Shift Options
.It \&%e Ta KEY_SPREVIOUS Ta Shift Previous Object
.It \&%f Ta KEY_SPRINT Ta Shift Print
.It \&%g Ta KEY_SREDO Ta Shift Redo
.It \&%h Ta KEY_SREPLACE Ta Shift Replace
.It \&%i Ta KEY_SRIGHT Ta Shift Right Arrow
.It \&%j Ta KEY_SRSUME Ta Shift Resume
.It \&&0 Ta KEY_SCANCEL Ta Shift Cancel
.It \&&1 Ta KEY_REFERENCE Ta Reference
.It \&&2 Ta KEY_REFRESH Ta Refresh
.It \&&3 Ta KEY_REPLACE Ta Replace
.It \&&4 Ta KEY_RESTART Ta Restart
.It \&&5 Ta KEY_RESUME Ta Resume
.It \&&6 Ta KEY_SAVE Ta Save
.It \&&7 Ta KEY_SUSPEND Ta Suspend
.It \&&8 Ta KEY_UNDO Ta Undo
.It \&&9 Ta KEY_SBEG Ta Shift Begin
.It \&*0 Ta KEY_SFIND Ta Shift Find
.It \&*1 Ta KEY_SCOMMAND Ta Shift Command
.It \&*2 Ta KEY_SCOPY Ta Shift Copy
.It \&*3 Ta KEY_SCREATE Ta Shift Create
.It \&*4 Ta KEY_SDC Ta Shift Delete Character
.It \&*5 Ta KEY_SDL Ta Shift Delete Line
.It \&*6 Ta KEY_SELECT Ta Select
.It \&*7 Ta KEY_SEND Ta Shift End
.It \&*8 Ta KEY_SEOL Ta Shift Clear to EOL
.It \&*9 Ta KEY_SEXIT Ta Shift Exit
.It \&@0 Ta KEY_FIND Ta Find
.It \&@1 Ta KEY_BEG Ta Begin
.It \&@2 Ta KEY_CANCEL Ta Cancel
.It \&@3 Ta KEY_CLOSE Ta Close
.It \&@4 Ta KEY_COMMAND Ta Command
.It \&@5 Ta KEY_COPY Ta Copy
.It \&@6 Ta KEY_CREATE Ta Create
.It \&@7 Ta KEY_END Ta End
.It \&@8 Ta KEY_ENTER Ta Enter
.It \&@9 Ta KEY_EXIT Ta Exit
.It \&F1 Ta KEY_F(11) Ta Function Key 11
.It \&F2 Ta KEY_F(12) Ta Function Key 12
.It \&F3 Ta KEY_F(13) Ta Function Key 13
.It \&F4 Ta KEY_F(14) Ta Function Key 14
.It \&F5 Ta KEY_F(15) Ta Function Key 15
.It \&F6 Ta KEY_F(16) Ta Function Key 16
.It \&F7 Ta KEY_F(17) Ta Function Key 17
.It \&F8 Ta KEY_F(18) Ta Function Key 18
.It \&F9 Ta KEY_F(19) Ta Function Key 19
.It \&FA Ta KEY_F(20) Ta Function Key 20
.It \&FB Ta KEY_F(21) Ta Function Key 21
.It \&FC Ta KEY_F(22) Ta Function Key 22
.It \&FD Ta KEY_F(23) Ta Function Key 23
.It \&FE Ta KEY_F(24) Ta Function Key 24
.It \&FF Ta KEY_F(25) Ta Function Key 25
.It \&FG Ta KEY_F(26) Ta Function Key 26
.It \&FH Ta KEY_F(27) Ta Function Key 27
.It \&FI Ta KEY_F(28) Ta Function Key 28
.It \&FJ Ta KEY_F(29) Ta Function Key 29
.It \&FK Ta KEY_F(30) Ta Function Key 30
.It \&FL Ta KEY_F(31) Ta Function Key 31
.It \&FM Ta KEY_F(32) Ta Function Key 32
.It \&FN Ta KEY_F(33) Ta Function Key 33
.It \&FO Ta KEY_F(34) Ta Function Key 34
.It \&FP Ta KEY_F(35) Ta Function Key 35
.It \&FQ Ta KEY_F(36) Ta Function Key 36
.It \&FR Ta KEY_F(37) Ta Function Key 37
.It \&FS Ta KEY_F(38) Ta Function Key 38
.It \&FT Ta KEY_F(39) Ta Function Key 39
.It \&FU Ta KEY_F(40) Ta Function Key 40
.It \&FV Ta KEY_F(41) Ta Function Key 41
.It \&FW Ta KEY_F(42) Ta Function Key 42
.It \&FX Ta KEY_F(43) Ta Function Key 43
.It \&FY Ta KEY_F(44) Ta Function Key 44
.It \&FZ Ta KEY_F(45) Ta Function Key 45
.It \&Fa Ta KEY_F(46) Ta Function Key 46
.It \&Fb Ta KEY_F(47) Ta Function Key 47
.It \&Fc Ta KEY_F(48) Ta Function Key 48
.It \&Fd Ta KEY_F(49) Ta Function Key 49
.It \&Fe Ta KEY_F(50) Ta Function Key 50
.It \&Ff Ta KEY_F(51) Ta Function Key 51
.It \&Fg Ta KEY_F(52) Ta Function Key 52
.It \&Fh Ta KEY_F(53) Ta Function Key 53
.It \&Fi Ta KEY_F(54) Ta Function Key 54
.It \&Fj Ta KEY_F(55) Ta Function Key 55
.It \&Fk Ta KEY_F(56) Ta Function Key 56
.It \&Fl Ta KEY_F(57) Ta Function Key 57
.It \&Fm Ta KEY_F(58) Ta Function Key 58
.It \&Fn Ta KEY_F(59) Ta Function Key 59
.It \&Fo Ta KEY_F(60) Ta Function Key 60
.It \&Fp Ta KEY_F(61) Ta Function Key 61
.It \&Fq Ta KEY_F(62) Ta Function Key 62
.It \&Fr Ta KEY_F(63) Ta Function Key 63
.It \&K1 Ta KEY_A1 Ta Upper left key in keypad
.It \&K2 Ta KEY_B2 Ta Centre key in keypad
.It \&K3 Ta KEY_A3 Ta Upper right key in keypad
.It \&K4 Ta KEY_C1 Ta Lower left key in keypad
.It \&K5 Ta KEY_C3 Ta Lower right key in keypad
.It \&Km Ta KEY_MOUSE Ta Mouse Event
.It \&k0 Ta KEY_F0 Ta Function Key 0
.It \&k1 Ta KEY_F(1) Ta Function Key 1
.It \&k2 Ta KEY_F(2) Ta Function Key 2
.It \&k3 Ta KEY_F(3) Ta Function Key 3
.It \&k4 Ta KEY_F(4) Ta Function Key 4
.It \&k5 Ta KEY_F(5) Ta Function Key 5
.It \&k6 Ta KEY_F(6) Ta Function Key 6
.It \&k7 Ta KEY_F(7) Ta Function Key 7
.It \&k8 Ta KEY_F(8) Ta Function Key 8
.It \&k9 Ta KEY_F(9) Ta Function Key 9
.It \&k; Ta KEY_F(10) Ta Function Key 10
.It \&kA Ta KEY_IL Ta Insert Line
.It \&ka Ta KEY_CATAB Ta Clear All Tabs
.It \&kB Ta KEY_BTAB Ta Back Tab
.It \&kb Ta KEY_BACKSPACE Ta Backspace
.It \&kC Ta KEY_CLEAR Ta Clear
.It \&kD Ta KEY_DC Ta Delete Character
.It \&kd Ta KEY_DOWN Ta Down Arrow
.It \&kE Ta KEY_EOL Ta Clear to End Of Line
.It \&kF Ta KEY_SF Ta Scroll Forward one line
.It \&kH Ta KEY_LL Ta Home Down
.It \&kh Ta KEY_HOME Ta Home
.It \&kI Ta KEY_IC Ta Insert Character
.It \&kL Ta KEY_DL Ta Delete Line
.It \&kl Ta KEY_LEFT Ta Left Arrow
.It \&kM Ta KEY_EIC Ta Exit Insert Character Mode
.It \&kN Ta KEY_NPAGE Ta Next Page
.It \&kP Ta KEY_PPAGE Ta Previous Page
.It \&kR Ta KEY_SR Ta Scroll One Line Back
.It \&kr Ta KEY_RIGHT Ta Right Arrow
.It \&kS Ta KEY_EOS Ta Clear to End Of Screen
.It \&kT Ta KEY_STAB Ta Set Tab
.It \&kt Ta KEY_CTAB Ta Clear Tab
.It \&ku Ta KEY_UP Ta Up Arrow
.El
.Pp
Note that not all terminals are capable of generating all the keycodes
listed above nor are terminfo entries normally configured with all the
above capabilities defined.
.Pp
Other functions that return an int will return one of the following
values:
.Pp
.Bl -tag -width ERR -compact
.It Er OK
The function completed successfully.
.It Er ERR
An error occurred in the function.
.El
.Pp
Functions returning pointers will return
.Dv NULL
if an error is detected.
.Sh SEE ALSO
.Xr curses_cursor 3 ,
.Xr curses_keyname 3 ,
.Xr curses_refresh 3 ,
.Xr curses_tty 3 ,
.Xr terminfo 5
.Sh STANDARDS
The
.Nx
Curses library complies with the X/Open Curses specification, part of the
Single Unix Specification.
.Sh NOTES
The
.Fn keyok
and
.Fn define_key
functions are implementations of extensions made by the NCurses library
to the Curses standard.
Portable implementations should avoid the use of these functions.
.Sh HISTORY
The Curses package appeared in
.Bx 4.0 .
The
.Fn is_keypad
and
.Fn set_tabsize
functions are
.Em ncurses
extension to the Curses library and was added in
.Nx 8.0 .