curs_util - Online Linux Manual Page

Section : 3X
Updated :

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

);

wchar_t *wunctrl(cchar_t *

);

const char *keyname(int

);

const char *key_name(wchar_t

);

void filter(void);

void nofilter(void);

void use_env(bool

);

void use_tioctl(bool

);

int putwin(WINDOW *

win

, FILE *

filep

);

WINDOW *getwin(FILE *

filep

);

int delay_output(int

);

int flushinp(void);

DESCRIPTION

unctrl

The unctrl

routine returns a character string which is a printable representation of the character

, ignoring attributes. Control characters are displayed in the

notation. Printing characters are displayed as is. The corresponding

wunctrl

returns a printable representation of a wide character.

keyname/key_name

The keyname

routine returns a character string corresponding to the key

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

• Control characters are displayed in the ^

notation.

• DEL (character 127) is displayed as ^?

• Values above 128 are either meta characters (if the screen has not been initialized, or if meta

(3X) has been called with a

TRUE

parameter), shown in the

M−

notation, or are displayed as themselves. In the latter case, the values may not be printable; this follows the X/Open specification.

• Values above 256 may be the names of the names of function keys.

• Otherwise (if there is no corresponding name) 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 character string corresponding to the wide-character value

. The two functions do not return the same set of strings; the latter returns null where the former would display a meta character.

filter/nofilter

The filter

routine, if used, must be called before

initscr

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

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

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

COLUMNS

environment variables, using a value in those to override the results from the operating system or terminal database.

Ncurses

also updates the screen size in response to

SIGWINCH

, unless overridden by the

LINES

COLUMNS

environment variables,

use_tioctl

The use_tioctl

routine, if used, should be called before

initscr

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 summarized here:

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.
TRUE	TRUE	ncurses updates $LINES and $COLUMNS based on operating system calls.
FALSE	TRUE	ncurses ignores $LINES and $COLUMNS, uses operating system calls to obtain size.
FALSE	FALSE	ncurses relies on the terminal database to determine 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

millisecond pause in output. This routine should not be used extensively because padding characters are used rather than a CPU pause. If no padding character is specified, this uses

napms

to perform the delay.

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

(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

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

(3X) 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

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

(3X) has been called with a

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

(3X) function allows the caller to change the output of

unctrl

Likewise, the meta

(3X) 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

(3X) and