Ubuntu Manpage: delay_output, filter, flushinp, getwin, key_name, keyname, nofilter, putwin, unctrl,

Provided by: ncurses-doc_6.4+20240113-1ubuntu2_all

NAME

       delay_output,  filter,  flushinp,  getwin,  key_name,  keyname,  nofilter, putwin, unctrl,
       use_env, use_tioctl, wunctrl - miscellaneous curses utility routines

SYNOPSIS

       #include <curses.h>

       const char *unctrl(chtype c);
       wchar_t *wunctrl(cchar_t *c);

       const char *keyname(int c);
       const char *key_name(wchar_t w);

       void filter(void);

       void use_env(bool f);

       int putwin(WINDOW *win, FILE *filep);
       WINDOW *getwin(FILE *filep);

       int delay_output(int ms);
       int flushinp(void);

       /* extensions */
       void nofilter(void);
       void use_tioctl(bool f);

DESCRIPTION

unctrl
The unctrl routine returns a character string which is a printable representation of the
character c:

• Printable characters are displayed as themselves, e.g., a one-character string
containing the key.

• Control characters are displayed in the ^X notation.

• Printing characters are displayed as is.

• DEL (character 127) is displayed as ^?.

• Values above 128 are either meta characters (if the screen has not been initialized,
or if meta(3NCURSES) has been called with a TRUE parameter), shown in the M-X
notation, or are displayed as themselves. In the latter case, the values may not be
printable; this follows the X/Open specification.

The corresponding wunctrl returns a printable representation of a complex character c.

In both unctrl and wunctrl the attributes and color associated with the character
parameter are ignored.

keyname, key_name
The keyname routine returns a character string corresponding to the key c. Key codes are
different from character codes.

• Key codes below 256 are characters. They are displayed using unctrl.

• Values above 256 may be the codes for function keys. The function key name is
displayed.

• Otherwise (if there is no corresponding name and the key is not a character) the
function returns null, to denote an error. X/Open also lists an “UNKNOWN KEY” return
value, which some implementations return rather than null.

The corresponding key_name returns a multibyte character string corresponding to the wide-
character value w. The two functions (keyname and key_name) do not return the same set of
strings:

• keyname returns null where key_name would display a meta character.

• key_name does not return the name of a function key.

filter, nofilter
The filter routine, if used, must be called before initscr or newterm are called. Calling
filter causes these changes in initialization:

• LINES is set to 1;

• the capabilities clear, cud1, cud, cup, cuu1, cuu, vpa are disabled;

• the capability ed is disabled if bce is set;

• and the home string is set to the value of cr.

The nofilter routine cancels the effect of a preceding filter call. That allows the
caller to initialize a screen on a different device, using a different value of $TERM.
The limitation arises because the filter routine modifies the in-memory copy of the
terminal information.

use_env
The use_env routine, if used, should be called before initscr or newterm are called
(because those compute the screen size). It modifies the way ncurses treats environment
variables when determining the screen size.

• Normally ncurses looks first at the terminal database for the screen size.

If use_env was called with FALSE for parameter, it stops here unless use_tioctl was
also called with TRUE for parameter.

• Then it asks for the screen size via operating system calls. If successful, it
overrides the values from the terminal database.

• Finally (unless use_env was called with FALSE parameter), ncurses examines the LINES
or COLUMNS environment variables, using a value in those to override the results from
the operating system or terminal database.

curses also updates the screen size in response to SIGWINCH, unless overridden by the
LINES or COLUMNS environment variables,

use_tioctl
The use_tioctl routine, if used, should be called before initscr or newterm are called
(because those compute the screen size). After use_tioctl is called with TRUE as an
argument, ncurses modifies the last step in its computation of screen size as follows:

• checks if the LINES and COLUMNS environment variables are set to a number greater than
zero.

• for each, ncurses updates the corresponding environment variable with the value that
it has obtained via operating system call or from the terminal database.

• ncurses re-fetches the value of the environment variables so that it is still the
environment variables which set the screen size.

The use_env and use_tioctl routines combine as follows.

use_env use_tioctl Summary
────────────────────────────────────────────────────────────────────────────────────

TRUE FALSE This is the default behavior. ncurses uses operating system
calls unless overridden by LINES or COLUMNS environment
variables; default.
TRUE TRUE ncurses updates LINES and COLUMNS based on operating system
calls.
FALSE TRUE ncurses ignores LINES and COLUMNS, using operating system
calls to obtain size.

putwin, getwin
The putwin routine writes all data associated with window (or pad) win into the file to
which filep points. This information can be later retrieved using the getwin function.

The getwin routine reads window related data stored in the file by putwin. The routine
then creates and initializes a new window using that data. It returns a pointer to the
new window. There are a few caveats:

• the data written is a copy of the WINDOW structure, and its associated character
cells. The format differs between the wide-character (ncursesw) and non-wide (‐
ncurses) libraries. You can transfer data between the two, however.

• the retrieved window is always created as a top-level window (or pad), rather than a
subwindow.

• the window's character cells contain the color pair value, but not the actual color
numbers. If cells in the retrieved window use color pairs which have not been created
in the application using init_pair, they will not be colored when the window is
refreshed.

delay_output
The delay_output routine inserts an ms millisecond pause in output. Employ this function
judiciously when terminal output uses padding, because ncurses transmits null characters
(consuming CPU and I/O resources) instead of sleeping and requesting resumption from the
operating system. Padding is used unless:

• the terminal description has npc (no_pad_char) capability, or

• the environment variable NCURSES_NO_PADDING is set.

If padding is not in use, ncurses uses napms to perform the delay. If the value of ms
exceeds 30,000 (thirty seconds), it is capped at that value.

flushinp
The flushinp routine throws away any typeahead that has been typed by the user and has not
yet been read by the program.

RETURN VALUE

       Except for flushinp, routines that return an integer return ERR upon failure and OK  (SVr4
       specifies only "an integer value other than ERR") upon successful completion.

       Routines that return pointers return NULL on error.

       X/Open does not define any error conditions.  In this implementation

          flushinp
               returns an error if the terminal was not initialized.

          putwin
               returns an error if the associated fwrite calls return an error.

PORTABILITY

filter
The SVr4 documentation describes the action of filter only in the vaguest terms. The
description here is adapted from the XSI Curses standard (which erroneously fails to
describe the disabling of cuu).

delay_output padding
The limitation to 30 seconds and the use of napms differ from other implementations.

• SVr4 curses does not delay if no padding character is available.

• NetBSD curses uses napms when no padding character is available, but does not take
timing into account when using the padding character.

Neither limits the delay.

keyname
The keyname function may return the names of user-defined string capabilities which are
defined in the terminfo entry via the -x option of tic. This implementation automatically
assigns at run-time keycodes to user-defined strings which begin with “k”. The keycodes
start at KEY_MAX, but are not guaranteed to be the same value for different runs because
user-defined codes are merged from all terminal descriptions which have been loaded. The
use_extended_names(3NCURSES) function controls whether this data is loaded when the
terminal description is read by the library.

nofilter, use_tioctl
The nofilter and use_tioctl routines are specific to ncurses. They were not supported on
Version 7, BSD or System V implementations. It is recommended that any code depending on
ncurses extensions be conditioned using NCURSES_VERSION.

putwin/getwin file-format
The putwin and getwin functions have several issues with portability:

• The files written and read by these functions use an implementation-specific format.
Although the format is an obvious target for standardization, it has been overlooked.

Interestingly enough, according to the copyright dates in Solaris source, the
functions (along with scr_init, etc.) originated with the University of California,
Berkeley (in 1982) and were later (in 1988) incorporated into SVr4. Oddly, there are
no such functions in the 4.3BSD curses sources.

• Most implementations simply dump the binary WINDOW structure to the file. These
include SVr4 curses, NetBSD and PDCurses, as well as older ncurses versions. This
implementation (as well as the X/Open variant of Solaris curses, dated 1995) uses
textual dumps.

The implementations which use binary dumps use block-I/O (the fwrite and fread
functions). Those that use textual dumps use buffered-I/O. A few applications may
happen to write extra data in the file using these functions. Doing that can run into
problems mixing block- and buffered-I/O. This implementation reduces the problem on
writes by flushing the output. However, reading from a file written using mixed
schemes may not be successful.

unctrl, wunctrl
The XSI Curses standard, Issue 4 describes these functions. It states that unctrl and
wunctrl will return a null pointer if unsuccessful, but does not define any error
conditions. This implementation checks for three cases:

• the parameter is a 7-bit US-ASCII code. This is the case that X/Open Curses
documented.

• the parameter is in the range 128-159, i.e., a C1 control code. If
use_legacy_coding(3NCURSES) has been called with a 2 parameter, unctrl returns the
parameter, i.e., a one-character string with the parameter as the first character.
Otherwise, it returns “~@”, “~A”, etc., analogous to “^@”, “^A”, C0 controls.

X/Open Curses does not document whether unctrl can be called before initializing
curses. This implementation permits that, and returns the “~@”, etc., values in that
case.

• parameter values outside the 0 to 255 range. unctrl returns a null pointer.

The strings returned by unctrl in this implementation are determined at compile time,
showing C1 controls from the upper-128 codes with a “~” prefix rather than “^”. Other
implementations have different conventions. For example, they may show both sets of
control characters with “^”, and strip the parameter to 7 bits. Or they may ignore C1
controls and treat all of the upper-128 codes as printable. This implementation uses 8
bits but does not modify the string to reflect locale. The use_legacy_coding(3NCURSES)
function allows the caller to change the output of unctrl.

Likewise, the meta(3NCURSES) function allows the caller to change the output of keyname,
i.e., it determines whether to use the “M-” prefix for “meta” keys (codes in the range 128
to 255). Both use_legacy_coding(3NCURSES) and meta(3NCURSES) succeed only after curses is
initialized. X/Open Curses does not document the treatment of codes 128 to 159. When
treating them as “meta” keys (or if keyname is called before initializing curses), this
implementation returns strings “M-^@”, “M-^A”, etc.

X/Open Curses documents unctrl as declared in <unctrl.h>, which ncurses does. However,
ncurses' <curses.h> includes <unctrl.h>, matching the behavior of SVr4 curses. Other
implementations may not do that.

use_env, use_tioctl
If ncurses is configured to provide the sp-functions extension, the state of use_env and
use_tioctl may be updated before creating each screen rather than once only (‐
sp_funcs(3NCURSES)). This feature of use_env is not provided by other implementations of
curses.

NAME

SYNOPSIS

DESCRIPTION

RETURN VALUE

PORTABILITY

SEE ALSO