'\" t
.\"***************************************************************************
-.\" Copyright (c) 1998-2015,2017 Free Software Foundation, Inc. *
+.\" Copyright 2018-2019,2020 Thomas E. Dickey *
+.\" Copyright 1998-2015,2017 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: ncurses.3x,v 1.128 2017/02/05 00:33:02 tom Exp $
+.\" $Id: ncurses.3x,v 1.150 2020/11/07 23:48:27 tom Exp $
.hy 0
.TH ncurses 3X ""
.ie \n(.g .ds `` \(lq
.ie \n(.g .ds '' \(rq
.el .ds '' ''
.de bP
-.IP \(bu 4
+.ie n .IP \(bu 4
+.el .IP \(bu 2
..
.de NS
-.ie \n(.sp
+.ie n .sp
.el .sp .5
-.ie \n(.in +4
+.ie n .in +4
.el .in +2
.nf
.ft C \" Courier
.de NE
.fi
.ft R
-.in -4
+.ie n .in -4
+.el .in -2
..
.ds n 5
.ds d @TERMINFO@
The library uses the locale which the calling program has initialized.
That is normally done with \fBsetlocale\fP:
.NS
- \fBsetlocale(LC_ALL, "");\fP
+\fBsetlocale(LC_ALL, "");\fP
.NE
+.PP
If the locale is not initialized,
the library assumes that characters are printable as in ISO\-8859\-1,
to work with certain legacy programs.
interactive, screen oriented programs want this), the following
sequence should be used:
.NS
- \fBinitscr(); cbreak(); noecho();\fR
+\fBinitscr(); cbreak(); noecho();\fR
.NE
+.PP
Most programs would additionally use the sequence:
.NS
- \fBnonl();\fR
- \fBintrflush(stdscr, FALSE);\fR
- \fBkeypad(stdscr, TRUE);\fR
+\fBintrflush(stdscr, FALSE);\fR
+\fBkeypad(stdscr, TRUE);\fR
.NE
+.PP
Before a \fBcurses\fR program is run, the tab stops of the terminal
should be set and its initialization strings, if defined, must be output.
This can be done by executing the \fB@TPUT@ init\fR command
For example, if \fBTERM\fR is set to \fBatt4424\fR, then the
compiled terminal definition is found in
.NS
- \fB\*d/a/att4424\fR.
+\fB\*d/a/att4424\fR.
.NE
+.PP
(The \fBa\fR is copied from the first letter of \fBatt4424\fR to avoid
creation of huge directories.) However, if \fBTERMINFO\fR is set to
\fB$HOME/myterms\fR, \fBcurses\fR first checks
.NS
- \fB$HOME/myterms/a/att4424\fR,
+\fB$HOME/myterms/a/att4424\fR,
.NE
+.PP
and if that fails, it then checks
.NS
- \fB\*d/a/att4424\fR.
+\fB\*d/a/att4424\fR.
.NE
+.PP
This is useful for developing experimental definitions or when write
permission in \fB\*d\fR is not available.
.PP
.RS 3
.TP 5
.I ncurses
-the "normal" library, which handles 8-bit characters.
+the \*(``normal\*('' library, which handles 8-bit characters.
The normal (8-bit) library stores characters combined with attributes
in \fBchtype\fP data.
.IP
Each cell (row and column) in a \fBWINDOW\fP is stored as a \fBchtype\fP.
.TP 5
.I ncursesw
-the so-called "wide" library, which handles multibyte characters
+the so-called \*(``wide\*('' library, which handles multibyte characters
(see the section on \fBALTERNATE CONFIGURATIONS\fP).
-The "wide" library includes all of the calls from the "normal" library.
+The \*(``wide\*('' library includes all of the calls
+from the \*(``normal\*('' library.
It adds about one third more calls using data types which store
multibyte characters:
.RS 5
The video attributes and color are stored in separate fields of the structure.
.IP
Each cell (row and column) in a \fBWINDOW\fP is stored as a \fBcchar_t\fP.
+.IP
+The \fBsetcchar\fP(3X) and \fBgetcchar\fP(3X)
+functions store and retrieve the data from
+a \fBcchar_t\fP structure.
.TP 5
.B wchar_t
-stores a "wide" character.
+stores a \*(``wide\*('' character.
Like \fBchtype\fP, this may be an integer.
.TP 5
.B wint_t
the same size.
.RE
.IP
-The "wide" library provides new functions which are analogous to
-functions in the "normal" library.
+The \*(``wide\*('' library provides new functions which are analogous to
+functions in the \*(``normal\*('' library.
There is a naming convention which relates many of the normal/wide variants:
-a "_w" is inserted into the name.
+a \*(``_w\*('' is inserted into the name.
For example, \fBwaddch\fP becomes \fBwadd_wch\fP.
.RE
.PP
.\"
.SS Routine Name Index
-The following table lists each \fBcurses\fR routine and the name of
-the manual page on which it is described.
-Routines flagged with `*'
+The following table lists the \fBcurses\fR routines provided in
+the \*(``normal\*('' and \*(``wide\*('' libraries and the names of
+the manual pages on which they are described.
+Routines flagged with \*(``*\*(''
are ncurses-specific, not described by XPG4 or present in SVr4.
.PP
.TS
=
COLOR_PAIR/\fBcurs_color\fR(3X)
PAIR_NUMBER/\fBcurs_attr\fR(3X)
-_nc_free_and_exit/\fBcurs_memleaks\fR(3X)*
-_nc_freeall/\fBcurs_memleaks\fR(3X)*
-_nc_tracebits/\fBcurs_trace\fR(3X)*
-_traceattr/\fBcurs_trace\fR(3X)*
-_traceattr2/\fBcurs_trace\fR(3X)*
-_tracechar/\fBcurs_trace\fR(3X)*
-_tracechtype/\fBcurs_trace\fR(3X)*
-_tracechtype2/\fBcurs_trace\fR(3X)*
-_tracedump/\fBcurs_trace\fR(3X)*
-_tracef/\fBcurs_trace\fR(3X)*
-_tracemouse/\fBcurs_trace\fR(3X)*
add_wch/\fBcurs_add_wch\fR(3X)
add_wchnstr/\fBcurs_add_wchstr\fR(3X)
add_wchstr/\fBcurs_add_wchstr\fR(3X)
addnwstr/\fBcurs_addwstr\fR(3X)
addstr/\fBcurs_addstr\fR(3X)
addwstr/\fBcurs_addwstr\fR(3X)
+alloc_pair/\fBnew_pair\fR(3X)*
assume_default_colors/\fBdefault_colors\fR(3X)*
attr_get/\fBcurs_attr\fR(3X)
attr_off/\fBcurs_attr\fR(3X)
color_set/\fBcurs_attr\fR(3X)
copywin/\fBcurs_overlay\fR(3X)
curs_set/\fBcurs_kernel\fR(3X)
+curses_trace/\fBcurs_trace\fR(3X)*
curses_version/\fBcurs_extend\fR(3X)*
def_prog_mode/\fBcurs_kernel\fR(3X)
def_shell_mode/\fBcurs_kernel\fR(3X)
erase/\fBcurs_clear\fR(3X)
erasechar/\fBcurs_termattrs\fR(3X)
erasewchar/\fBcurs_termattrs\fR(3X)
+exit_curses/\fBcurs_memleaks\fR(3X)*
+exit_terminfo/\fBcurs_memleaks\fR(3X)*
+extended_color_content/\fBcurs_color\fR(3X)*
+extended_pair_content/\fBcurs_color\fR(3X)*
+extended_slk_color/\fBcurs_slk\fR(3X)*
filter/\fBcurs_util\fR(3X)
+find_pair/\fBnew_pair\fR(3X)*
flash/\fBcurs_beep\fR(3X)
flushinp/\fBcurs_util\fR(3X)
+free_pair/\fBnew_pair\fR(3X)*
get_wch/\fBcurs_get_wch\fR(3X)
get_wstr/\fBcurs_get_wstr\fR(3X)
getattrs/\fBcurs_attr\fR(3X)
has_ic/\fBcurs_termattrs\fR(3X)
has_il/\fBcurs_termattrs\fR(3X)
has_key/\fBcurs_getch\fR(3X)*
+has_mouse/\fBcurs_mouse\fR(3X)*
hline/\fBcurs_border\fR(3X)
hline_set/\fBcurs_border_set\fR(3X)
idcok/\fBcurs_outopts\fR(3X)
inchnstr/\fBcurs_inchstr\fR(3X)
inchstr/\fBcurs_inchstr\fR(3X)
init_color/\fBcurs_color\fR(3X)
+init_extended_color/\fBcurs_color\fR(3X)*
+init_extended_pair/\fBcurs_color\fR(3X)*
init_pair/\fBcurs_color\fR(3X)
initscr/\fBcurs_initscr\fR(3X)
innstr/\fBcurs_instr\fR(3X)
nodelay/\fBcurs_inopts\fR(3X)
noecho/\fBcurs_inopts\fR(3X)
nofilter/\fBcurs_util\fR(3X)*
-nonl/\fBcurs_outopts\fR(3X)
+nonl/\fBcurs_inopts\fR(3X)
noqiflush/\fBcurs_inopts\fR(3X)
noraw/\fBcurs_inopts\fR(3X)
notimeout/\fBcurs_inopts\fR(3X)
overlay/\fBcurs_overlay\fR(3X)
overwrite/\fBcurs_overlay\fR(3X)
pair_content/\fBcurs_color\fR(3X)
+pecho_wchar/\fBcurs_pad\fR(3X)*
pechochar/\fBcurs_pad\fR(3X)
pnoutrefresh/\fBcurs_pad\fR(3X)
prefresh/\fBcurs_pad\fR(3X)
raw/\fBcurs_inopts\fR(3X)
redrawwin/\fBcurs_refresh\fR(3X)
refresh/\fBcurs_refresh\fR(3X)
+reset_color_pairs/\fBcurs_color\fR(3X)*
reset_prog_mode/\fBcurs_kernel\fR(3X)
reset_shell_mode/\fBcurs_kernel\fR(3X)
resetty/\fBcurs_kernel\fR(3X)
slk_restore/\fBcurs_slk\fR(3X)
slk_set/\fBcurs_slk\fR(3X)
slk_touch/\fBcurs_slk\fR(3X)
+slk_wset/\fBcurs_slk\fR(3X)*
standend/\fBcurs_attr\fR(3X)
standout/\fBcurs_attr\fR(3X)
start_color/\fBcurs_color\fR(3X)
tigetflag/\fBcurs_terminfo\fR(3X)
tigetnum/\fBcurs_terminfo\fR(3X)
tigetstr/\fBcurs_terminfo\fR(3X)
-tiparm/\fBcurs_terminfo\fR(3X)*
timeout/\fBcurs_inopts\fR(3X)
+tiparm/\fBcurs_terminfo\fR(3X)*
touchline/\fBcurs_touch\fR(3X)
touchwin/\fBcurs_touch\fR(3X)
tparm/\fBcurs_terminfo\fR(3X)
use_env/\fBcurs_util\fR(3X)
use_extended_names/\fBcurs_extend\fR(3X)*
use_legacy_coding/\fBlegacy_coding\fR(3X)*
-use_tioctl/\fBcurs_util\fR(3X)
+use_tioctl/\fBcurs_util\fR(3X)*
vid_attr/\fBcurs_terminfo\fR(3X)
vid_puts/\fBcurs_terminfo\fR(3X)
vidattr/\fBcurs_terminfo\fR(3X)
wvline/\fBcurs_border\fR(3X)
wvline_set/\fBcurs_border_set\fR(3X)
.TE
+.PP
+Depending on the configuration,
+additional sets of functions may be available:
+.RS 3
+.TP 5
+\fBcurs_memleaks\fP(3X) - curses memory-leak checking
+.TP 5
+\fBcurs_sp_funcs\fP(3X) - curses screen-pointer extension
+.TP 5
+\fBcurs_threads\fP(3X) - curses thread support
+.TP 5
+\fBcurs_trace\fP(3X) - curses debugging routines
+.RE
.SH RETURN VALUE
Routines that return an integer return \fBERR\fR upon failure and an
integer value other than \fBERR\fR upon successful completion, unless
\fBgetmaxyx\fR are undefined (i.e., these should not be used as the
right-hand side of assignment statements).
.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.
+Most \*(``mv\*(''-prefixed functions
+(except variadic functions such as \fBmvprintw\fP)
+are provided both as macros and functions.
+.PP
Routines that return pointers return \fBNULL\fR on error.
.SH ENVIRONMENT
+.PP
The following environment symbols are useful for customizing the
runtime behavior of the \fBncurses\fR library.
The most important ones have been already discussed in detail.
-.SS CC
+.SS CC command-character
+.PP
When set, change occurrences of the command_character
(i.e., the \fBcmdch\fP capability)
of the loaded terminfo entries to the value of this variable.
the C compiler's name, \fBncurses\fR ignores it if it does not happen to
be a single character.
.SS BAUDRATE
+.PP
The debugging library checks this environment variable when the application
has redirected output to a file.
The variable's numeric value is used for the baudrate.
This allows testers to construct repeatable test-cases
that take into account costs that depend on baudrate.
.SS COLUMNS
+.PP
Specify the width of the screen in characters.
Applications running in a windowing environment usually are able to
obtain the width of the window in which they are executing.
Use the \fBuse_tioctl\fR function to update \fBCOLUMNS\fP or \fBLINES\fP
to match the screen size obtained from system calls or the terminal database.
.SS ESCDELAY
+.PP
Specifies the total time, in milliseconds, for which ncurses will
await a character sequence, e.g., a function key.
The default value, 1000 milliseconds, is enough for most uses.
.SS HOME
Tells \fBncurses\fR where your home directory is.
That is where it may read and write auxiliary terminal descriptions:
-.PP
+.NS
$HOME/.termcap
-.br
$HOME/.terminfo
+.NE
.SS LINES
+.PP
Like COLUMNS, specify the height of the screen in characters.
See COLUMNS for a detailed description.
.SS MOUSE_BUTTONS_123
+.PP
This applies only to the OS/2 EMX port.
It specifies the order of buttons on the mouse.
OS/2 numbers a 3-button mouse inconsistently from other
platforms:
-.sp
+.NS
1 = left
.br
2 = right
.br
3 = middle.
-.sp
+.NE
+.PP
This variable lets you customize the mouse.
The variable must be three numeric digits 1\-3 in any order, e.g., 123 or 321.
If it is not specified, \fBncurses\fR uses 132.
.SS NCURSES_ASSUMED_COLORS
+.PP
Override the compiled-in assumption that the
terminal's default colors are white-on-black
(see \fBdefault_colors\fR(3X)).
explicitly saving and restoring the original screen contents.
Setting the environment variable \fBNCGDB\fP has the same effect.
.SS NCURSES_GPM_TERMS
+.PP
This applies only to ncurses configured to use the GPM interface.
.PP
If present,
using the built-in support for xterm, etc.
.PP
If the environment variable is absent,
-ncurses will attempt to open GPM if \fBTERM\fP contains "linux".
+ncurses will attempt to open GPM if \fBTERM\fP contains \*(``linux\*(''.
.SS NCURSES_NO_HARD_TABS
+.PP
\fBNcurses\fP may use tabs as part of the cursor movement optimization.
In some cases,
your terminal driver may not handle these properly.
Set this environment variable to disable the feature.
You can also adjust your \fBstty\fP settings to avoid the problem.
-NCURSES_NO_MAGIC_COOKIE
+.SS NCURSES_NO_MAGIC_COOKIE
+.PP
Some terminals use a magic-cookie feature which requires special handling
to make highlighting and other video attributes display properly.
You can suppress the highlighting entirely for these terminals by
setting this environment variable.
.SS NCURSES_NO_PADDING
+.PP
Most of the terminal descriptions in the terminfo database are written
-for real "hardware" terminals.
+for real \*(``hardware\*('' terminals.
Many people use terminal emulators
which run in a windowing environment and use curses-based applications.
Terminal emulators can duplicate
standard output.
But high-level curses calls do not.
.SS NCURSES_NO_UTF8_ACS
+.PP
During initialization, the \fBncurses\fR library
checks for special cases where VT100 line-drawing (and the corresponding
alternate character set capabilities) described in the terminfo are known
.PP
When setting this variable, you should set it to a nonzero value.
Setting it to zero (or to a nonnumber)
-disables the special check for "linux" and "screen".
+disables the special check for \*(``linux\*('' and \*(``screen\*(''.
.PP
As an alternative to the environment variable,
ncurses checks for an extended terminfo capability \fBU8\fP.
.ft
.RE
.PP
-The name "U8" is chosen to be two characters,
+The name \*(``U8\*('' is chosen to be two characters,
to permit it to be used by applications that use ncurses'
termcap interface.
.SS NCURSES_TRACE
+.PP
During initialization, the \fBncurses\fR debugging library
checks the NCURSES_TRACE environment variable.
If it is defined, to a numeric value, \fBncurses\fR calls the \fBtrace\fR
.PP
See \fBcurs_trace\fP(3X) for more information.
.SS TERM
+.PP
Denotes your terminal type.
Each terminal type is distinct, though many are similar.
.PP
support, \fBncurses\fR will check for a terminal's description in
termcap form if it is not available in the terminfo database.
.PP
-The \fBTERMCAP\fP environment variable contains either a terminal description (with
-newlines stripped out),
+The \fBTERMCAP\fP environment variable contains
+either a terminal description (with newlines stripped out),
or a file name telling where the information denoted by
the \fBTERM\fP environment variable exists.
In either case, setting it directs \fBncurses\fR to ignore
the usual place for this information, e.g., /etc/termcap.
.SS TERMINFO
+.PP
\fBncurses\fP can be configured to read from multiple terminal databases.
-The \fBTERMINFO\fP variable overrides the location for the default terminal database.
+The \fBTERMINFO\fP variable overrides the location for
+the default terminal database.
Terminal descriptions (in terminal format) are stored in terminal databases:
.bP
Normally these are stored in a directory tree,
.RE
.PP
.SS TERMINFO_DIRS
+.PP
Specifies a list of locations to search for terminal descriptions.
Each location in the list is a terminal database as described in
the section on the \fBTERMINFO\fP variable.
There is no corresponding feature in System V terminfo;
it is an extension developed for \fBncurses\fP.
.SS TERMPATH
+.PP
If \fBTERMCAP\fP does not hold a file name then \fBncurses\fR checks
the \fBTERMPATH\fP environment variable.
This is a list of filenames separated by spaces or colons (i.e., ":") on Unix,
$TERMINFO, $TERMINFO_DIRS, $TERMPATH, as well as $HOME.
.NE
.SH ALTERNATE CONFIGURATIONS
+.PP
Several different configurations are possible,
depending on the configure script options used when building \fBncurses\fP.
There are a few main options whose effects are visible to the applications
.TP 5
\-\-disable\-overwrite
The standard include for \fBncurses\fP is as noted in \fBSYNOPSIS\fP:
-.RS 3
-.sp
+.NS
\fB#include <curses.h>\fR
-.RE
+.NE
.IP
This option is used to avoid filename conflicts when \fBncurses\fP
is not the main implementation of curses of the computer.
If \fBncurses\fP is installed disabling overwrite, it puts its headers in
a subdirectory, e.g.,
-.RS 3
-.sp
+.NS
\fB#include <ncurses/curses.h>\fR
-.RE
+.NE
.IP
It also omits a symbolic link which would allow you to use \fB\-lcurses\fP
to build executables.
The configure script renames the library and
(if the \fB\-\-disable\-overwrite\fP option is used)
puts the header files in a different subdirectory.
-All of the library names have a "w" appended to them,
+All of the library names have a \*(``w\*('' appended to them,
i.e., instead of
-.RS 3
-.sp
+.NS
\fB\-lncurses\fR
-.RE
+.NE
.IP
you link with
-.RS 3
-.sp
+.NS
\fB\-lncursesw\fR
+.NE
+.IP
+You must also enable the wide-character features in the header file
+when compiling for the wide-character library
+to use the extended (wide-character) functions.
+The symbol which enables these features has changed since XSI Curses, Issue 4:
+.RS
+.bP
+Originally, the wide-character feature required the symbol
+\fB_XOPEN_SOURCE_EXTENDED\fP
+but that was only valid for XPG4 (1996).
+.bP
+Later, that was deemed conflicting with \fB_XOPEN_SOURCE\fP defined to 500.
+.bP
+As of mid-2018,
+none of the features in this implementation require a \fB_XOPEN_SOURCE\fP
+feature greater than 600.
+However, X/Open Curses, Issue 7 (2009) recommends defining it to 700.
+.bP
+Alternatively, you can enable the feature by defining \fBNCURSES_WIDECHAR\fP
+with the caveat that some other header file than \fBcurses.h\fP
+may require a specific value for \fB_XOPEN_SOURCE\fP
+(or a system-specific symbol).
.RE
.IP
-You must also define \fB_XOPEN_SOURCE_EXTENDED\fP when compiling for the
-wide-character library to use the extended (wide-character) functions.
The \fBcurses.h\fP file which is installed for the wide-character
library is designed to be compatible with the normal library's header.
Only the size of the \fBWINDOW\fP structure differs, and very few
applications require more than a pointer to \fBWINDOW\fPs.
+.IP
If the headers are installed allowing overwrite,
the wide-character library's headers should be installed last,
to allow applications to be built using either library
.TP 5
\-\-with\-pthread
The configure script renames the library.
-All of the library names have a "t" appended to them
-(before any "w" added by \fB\-\-enable\-widec\fP).
+All of the library names have a \*(``t\*('' appended to them
+(before any \*(``w\*('' added by \fB\-\-enable\-widec\fP).
.IP
The global variables such as \fBLINES\fP are replaced by macros to
allow read-only access.
\-\-with\-profile
The shared and normal (static) library names differ by their suffixes,
e.g., \fBlibncurses.so\fP and \fBlibncurses.a\fP.
-The debug and profiling libraries add a "_g" and a "_p" to the root
-names respectively,
+The debug and profiling libraries add a \*(``_g\*(''
+and a \*(``_p\*('' to the root names respectively,
e.g., \fBlibncurses_g.a\fP and \fBlibncurses_p.a\fP.
.TP 5
+\-\-with\-termlib
+Low-level functions which do not depend upon whether the library
+supports wide-characters, are provided in the tinfo library.
+.IP
+By doing this, it is possible to share the tinfo library between
+wide/normal configurations as well as reduce the size of the library
+when only low-level functions are needed.
+.IP
+Those functions are described in these pages:
+.RS
+.bP
+\fBcurs_extend\fP(3X) \- miscellaneous curses extensions
+.bP
+\fBcurs_inopts\fR(3X) \- \fBcurses\fR input options
+.bP
+\fBcurs_kernel\fR(3X) \- low-level \fBcurses\fR routines
+.bP
+\fBcurs_termattrs\fR(3X) \- \fBcurses\fR environment query routines
+.bP
+\fBcurs_termcap\fR(3X) \- \fBcurses\fR emulation of termcap
+.bP
+\fBcurs_terminfo\fR(3X) \- \fBcurses\fR interfaces to terminfo database
+.bP
+\fBcurs_util\fR(3X) \- miscellaneous \fBcurses\fR utility routines
+.RE
+.TP 5
\-\-with\-trace
The \fBtrace\fP function normally resides in the debug library,
but it is sometimes useful to configure this in the shared library.
terminal capability database
.SH SEE ALSO
\fBterminfo\fR(\*n) and related pages whose names begin
-"curs_" for detailed routine descriptions.
+\*(``curs_\*('' for detailed routine descriptions.
.br
\fBcurs_variables\fR(3X)
+.br
+\fBuser_caps\fP(5) for user-defined capabilities
.SH EXTENSIONS
The \fBncurses\fR library can be compiled with an option (\fB\-DUSE_GETCAP\fR)
that falls back to the old-style /etc/termcap file if the terminal setup code
resizing events, e.g., when running in an xterm.
See the \fBresizeterm\fR(3X)
and \fBwresize\fR(3X) manual pages for details.
-In addition, the library may be configured with a SIGWINCH handler.
+In addition, the library may be configured with a \fBSIGWINCH\fP handler.
.PP
The \fBncurses\fR library extends the fixed set of function key capabilities
of terminals by allowing the application designer to define additional
A small number of local differences (that is, individual differences between
the XSI Curses and \fBncurses\fR calls) are described in \fBPORTABILITY\fR
sections of the library man pages.
+.SS Error checking
+.PP
+In many cases, X/Open Curses is vague about error conditions,
+omitting some of the SVr4 documentation.
.PP
Unlike other implementations, this one checks parameters such as pointers
to WINDOW structures to ensure they are not null.
to tell an application which of several possible errors were detected.
Relying on this (or some other) extension will adversely affect the
portability of curses applications.
+.SS Extensions versus portability
.PP
-This implementation also contains several extensions:
+Most of the extensions provided by ncurses have not been standardized.
+Some have been incorporated into other implementations, such as
+PDCurses or NetBSD curses.
+Here are a few to consider:
.bP
The routine \fBhas_key\fR is not part of XPG4, nor is it present in SVr4.
See the \fBcurs_getch\fR(3X) manual page for details.
This implementation can also be configured to provide a set of functions which
improve the ability to manage multiple screens.
See \fBcurs_sp_funcs\fR(3X) for details.
+.SS Padding differences
.PP
In historic curses versions, delays embedded in the capabilities \fBcr\fR,
\fBind\fR, \fBcub1\fR, \fBff\fR and \fBtab\fR activated corresponding delay
This method is slightly more expensive, but narrows the interface
to the UNIX kernel significantly and increases the package's portability
correspondingly.
-.SH NOTES
+.SS Header files
The header file \fB<curses.h>\fR automatically includes the header files
\fB<stdio.h>\fR and \fB<unctrl.h>\fR.
.PP
+X/Open Curses has more to say,
+but does not finish the story:
+.RS 4
+.PP
+The inclusion of <curses.h> may make visible all symbols
+from the headers <stdio.h>, <term.h>, <termios.h>, and <wchar.h>.
+.RE
+.PP
+Here is a more complete story:
+.bP
+Starting with BSD curses, all implementations have included <stdio.h>.
+.IP
+BSD curses included <curses.h> and <unctrl.h> from an internal header
+"curses.ext" ("ext" was a short name for \fIexterns\fP).
+.IP
+BSD curses used <stdio.h> internally (for \fBprintw\fP and \fBscanw\fP),
+but nothing in <curses.h> itself relied upon <stdio.h>.
+.bP
+SVr2 curses added \fBnewterm\fP(3X), which relies upon <stdio.h>.
+That is, the function prototype uses \fBFILE\fP.
+.IP
+SVr4 curses added \fBputwin\fP and \fBgetwin\fP, which also use <stdio.h>.
+.IP
+X/Open Curses documents all three of these functions.
+.IP
+SVr4 curses and X/Open Curses do not require the developer to
+include <stdio.h> before including <curses.h>.
+Both document curses showing <curses.h> as the only required header.
+.IP
+As a result, standard <curses.h> will always include <stdio.h>.
+.bP
+X/Open Curses is inconsistent with respect to SVr4 regarding <unctrl.h>.
+.IP
+As noted in \fBcurs_util\fP(3X), ncurses includes <unctrl.h> from
+<curses.h> (like SVr4).
+.bP
+X/Open's comments about <term.h> and <termios.h> may refer to HP-UX and AIX:
+.IP
+HP-UX curses includes <term.h> from <curses.h>
+to declare \fBsetupterm\fP in curses.h,
+but ncurses (and Solaris curses) do not.
+.IP
+AIX curses includes <term.h> and <termios.h>.
+Again, ncurses (and Solaris curses) do not.
+.bP
+X/Open says that <curses.h> \fImay\fP include <term.h>,
+but there is no requirement that it do that.
+.IP
+Some programs use functions declared in both <curses.h> and <term.h>,
+and must include both headers in the same module.
+Very old versions of AIX curses required including <curses.h>
+before including <term.h>.
+.IP
+Because ncurses header files include the headers needed to
+define datatypes used in the headers,
+ncurses header files can be included in any order.
+But for portability, you should include <curses.h> before <term.h>.
+.bP
+X/Open Curses says \fI"may make visible"\fP
+because including a header file does not necessarily make all symbols
+in it visible (there are ifdef's to consider).
+.IP
+For instance, in ncurses <wchar.h> \fImay\fP be included if
+the proper symbol is defined, and if ncurses is configured for
+wide-character support.
+If the header is included, its symbols may be made visible.
+That depends on the value used for \fB_XOPEN_SOURCE\fP
+feature test macro.
+.bP
+X/Open Curses documents one required header,
+in a special case: <stdarg.h> before <curses.h> to prototype
+the \fBvw_printw\fP and \fBvw_scanw\fP functions
+(as well as the obsolete
+the \fBvwprintw\fP and \fBvwscanw\fP functions).
+Each of those uses a \fBva_list\fP parameter.
+.IP
+The two obsolete functions were introduced in SVr3.
+The other functions were introduced in X/Open Curses.
+In between, SVr4 curses provided for the possibility that
+an application might include either <varargs.h> or <stdarg.h>.
+Initially, that was done by using \fBvoid*\fP for the \fBva_list\fP
+parameter.
+Later, a special type (defined in <stdio.h>) was introduced,
+to allow for compiler type-checking.
+That special type is always available,
+because <stdio.h> is always included by <curses.h>.
+.IP
+None of the X/Open Curses implementations require an application
+to include <stdarg.h> before <curses.h> because they either
+have allowed for a special type, or (like ncurses) include <stdarg.h>
+directly to provide a portable interface.
+.SH NOTES
+.PP
If standard output from a \fBncurses\fR program is re-directed to something
which is not a tty, screen updates will be directed to standard error.
This was an undocumented feature of AT&T System V Release 3 curses.
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