curs_util
Section: Library calls (3X)
Updated: 202-1-11
Index
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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 ch);
wchar_t * wunctrl(cchar_t * wch);
const char * keyname(int c);
const char * key_name(wchar_t wc);
void filter(void);
/* extension */
void nofilter(void);
void use_env(bool bf);
/* extension */
void use_tioctl(bool bf);
int putwin(WINDOW * win, FILE * filep);
WINDOW * getwin(FILE * filep);
int delay_output(int ms);
int flushinp(void);
DESCRIPTION
unctrl, wunctrl
unctrl
returns a nul-terminated character string printably representing the
curses
character
ch,
often one that originated in keyboard input;
see
getch(3X).
.IP * 4
Printable characters represent themselves as a on-character string.
.IP * 4
Control characters are expressed in
^X
notation,
where
X
is the printable symbol of the control code's value plus 32
in the ISO 646/"ASCII" character set.
.IP * 4
DEL
(character code 127)
is represented as
^?.
.IP * 4
A character code greater than 127 is represented in one of two ways.
-
If the screen has not been initialized or is in meta mode
(see meta(3X)),
it is expressed in
-X
notation,
where X
is the representation of the code's value minus 128,
as described above.
-
If the screen is not in meta mode,
the character code is assumed to represent itself.
It nevertheless may not be printable;
this is the case for character codes 12-159 in ISO 8859 encodings.
-
ncurses's
use_legacy_coding(3X)
function configures
unctrl's
handling of these character codes.
wunctrl
returns a nul-terminated wid-character string printably representing
the
curses
complex character
wch.
Both functions ignore the attributes and color pair selection
of their argument.
keyname, key_name
The
keyname routine returns a character string
corresponding to the key
c.
Key codes are different from character codes.
.IP * 4
Key codes below 256 are characters.
They are displayed using
unctrl.
.IP * 4
Values above 256 may be the codes for function keys.
The function key name is displayed.
.IP * 4
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 wid-character value wc.
The two functions
(keyname and key_name)
do not return the same set of strings:
.IP * 4
keyname returns null where key_name
would display a meta character.
.IP * 4
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:
.IP * 4
LINES is set to 1;
.IP * 4
the capabilities
clear,
cud1,
cud,
cup,
cuu1,
cuu,
vpa
are disabled;
.IP * 4
the capability
ed is disabled if
bce is set;
.IP * 4
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
i-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.
.IP * 4
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.
.IP * 4
Then it asks for the screen size via operating system calls.
If successful,
it overrides the values from the terminal database.
.IP * 4
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:
.IP * 4
checks whether the
LINES and
COLUMNS environment variables
are set to a number greater than zero.
.IP * 4
for each,
ncurses updates the corresponding environment variable
with the value that it has obtained via operating system call
or from the terminal database.
.IP * 4
ncurses r-fetches the value of the environment variables so
that it is still the environment variables that set the screen size.
The use_env and use_tioctl routines combine as follows.
-
| use_env | use_tioctl | Summary
|
|
| TRUE | FALSE |
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:
.IP * 4
the data written is a copy of the WINDOW structure,
and its associated character cells.
The format differs between the wid-character (ncursesw) and
no-wide (ncurses) libraries.
You can transfer data between the two,
however.
.IP * 4
the retrieved window is always created as a to-level window
(or pad),
rather than a subwindow.
.IP * 4
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 that 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:
.IP * 4
the terminal description has
npc (
no_pad_char) capability,
or
.IP * 4
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,
functions that return integers return
ERR
upon failure and
OK
upon success.
Functions that return pointers return a null pointer on failure.
In
ncurses,
.IP * 4
flushinp
returns
ERR
if the terminal was not initialized,
and
.IP * 4
putwin
returns
ERR
if its associated write(2) calls return
ERR.
NOTES
wunctrl
is part of
ncurses's
wid-character API,
and is not available in its no-wid-character configuration.
PORTABILITY
X/Open Curses Issue 4 describes these functions.
It specifies no error conditions for them.
SVr4 describes a successful return value only as
"an integer value other than
ERR".
filter
The SVr4 documentation describes the action of
filter
only in the vaguest terms.
The description here is adapted from X/Open Curses
(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.
.IP * 4
SVr4
curses
does not delay if no padding character is available.
.IP * 4
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 use-defined
string capabilities that are defined in the terminfo entry
via the
-x
option of
tic.
This implementation automatically assigns at ru-time key codes to
use-defined strings that begin with "k".
The key codes start at KEY_MAX,
but are not guaranteed to be the same value for different runs
because use-defined codes are merged
from all terminal descriptions that 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 fil-format
The
putwin and
getwin functions have several issues with
portability:
.IP * 4
The files written and read by these functions
use an implementatio-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.
.IP * 4
Most implementations simply dump the binary
WINDOW
structure
to the file.
These include SVr4
curses,
NetBSD
curses,
and
PDCurses,
as well as older ncurses versions.
This implementation
(as well as
xcurses,
the X/Open variant of Solaris
curses,
dated 1995)
uses textual dumps.
-
The implementations that use binary dumps use block I/O
(write(2) and read(2) 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
X/Open Curses Issue 4 describes these functions.
It specifies no error conditions for them.
It states that
unctrl and
wunctrl will return a null pointer
if unsuccessful.
This implementation checks for three cases:
.IP * 4
the parameter is a -bit US-ASCII code.
This is the case that X/Open Curses documented.
.IP * 4
the parameter is in the range 128-159,
i.e.,
a C1 control code.
If
use_legacy_coding(3X) has been called with a
2 parameter,
unctrl returns the parameter,
i.e.,
a on-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.
.IP * 4
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 uppe-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 uppe-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 meta(3X) 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's
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 s-functions extension,
the state of
use_env and
use_tioctl may be updated before
creating each
screen rather than once only
(
curs_sp_funcs(3X)).
This feature of
use_env
is not provided by other implementations of
curses.
HISTORY
4BSD (1980)
introduced
unctrl,
defining it as a macro
in
unctrl.h.
SVr2 (1984)
added
delay_output,
flushinp,
and
keyname.
SVr3 (1987) supplied
filter.
Later that year,
SVr3.1 brought
getwin
and
putwin,
reading and writing window dumps
with fread(3) and fwrite(3),
respectively.
SVr4 (1989) furnished
use_env.
X/Open Curses Issue 4 (1995) specified
key_name
and
wunctrl.
ncurses
5.6 (2006) added
nofilter,
and 6.0 (2015)
use_tioctl.
SEE ALSO
curses(3X),
curs_initscr(3X),
curs_inopts(3X),
curs_kernel(3X),
curs_scr_dump(3X),
curs_sp_funcs(3X),
curs_variables(3X),
legacy_coding(3X)
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- unctrl, wunctrl
-
- keyname, key_name
-
- filter, nofilter
-
- use_env
-
- use_tioctl
-
- putwin, getwin
-
- delay_output
-
- flushinp
-
- RETURN VALUE
-
- NOTES
-
- PORTABILITY
-
- filter
-
- delay_output padding
-
- keyname
-
- nofilter, use_tioctl
-
- putwin/getwin file-format
-
- unctrl, wunctrl
-
- use_env, use_tioctl
-
- HISTORY
-
- SEE ALSO
-
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