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>
char *unctrl(chtype c);
wchar_t *wunctrl(cchar_t *c);
char *keyname(int c);
char *key_name(wchar_t w);
void filter(void);
void nofilter(void);
void use_env(bool f);
void use_tioctl(bool f);
int putwin(WINDOW *win, FILE *filep);
WINDOW *getwin(FILE *filep);
int delay_output(int ms);
int flushinp(void);
DESCRIPTION¶
The
unctrl routine returns a character string which is a printable
representation of the character
c, ignoring attributes. Control
characters are displayed in the
^X notation. Printing characters
are displayed as is. The corresponding
wunctrl returns a printable
representation of a wide character.
The
keyname routine returns a character string corresponding to the key
c:
- •
- Printable characters are displayed as themselves, e.g., a one-character
string containing the key.
- •
- Control characters are displayed in the ^X notation.
- •
- DEL (character 127) is displayed as ^?.
- •
- Values above 128 are either meta characters (if the screen has not been
initialized, or if meta 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.
- •
- 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
w. The two functions do not return the same
set of strings; the latter returns null where the former would display a meta
character.
The
filter routine, if used, must be called before
initscr or
newterm are called. The effect is that, during those calls,
LINES is set to 1; the capabilities
clear,
cup,
cud,
cud1,
cuu1,
cuu,
vpa are disabled; 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.
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 If 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.
- Ncurses also updates the screen size in response to SIGWINCH, unless
overridden by the LINES or COLUMNS environment
variables,
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 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. |
The
putwin routine writes all data associated with window
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.
The
delay_output routine inserts an
ms 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.
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.
- meta
- returns an error if the terminal was not initialized.
- putwin
- returns an error if the associated fwrite calls return an
error.
PORTABILITY¶
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 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 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).
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 function
allows the caller to change the output of
unctrl.
Likewise, the
meta 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 and
meta 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.
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 function controls whether this
data is loaded when the terminal description is read by the library.
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.
SEE ALSO¶
legacy_coding(3NCURSES),
ncurses(3NCURSES),
initscr(3NCURSES),
kernel(3NCURSES),
scr_dump(3NCURSES),
curses_variables(3NCURSES),
legacy_coding(3NCURSES).