curs_util(3x) curs_util(3x)
delay_output, filter, flushinp, getwin, key_name, keyname,
nofilter, putwin, unctrl, use_env, use_tioctl, wunctrl -
miscellaneous curses utility routines
#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);
The unctrl routine returns a character string which is a
printable representation of the character c, ignoring at-
tributes. Control characters are displayed in the ^X no-
tation. Printing characters are displayed as is. The
corresponding wunctrl returns a printable representation
of a wide character.
The keyname routine returns a character string correspond-
ing to the key c:
o Printable characters are displayed as themselves,
e.g., a one-character string containing the key.
o Control characters are displayed in the ^X notation.
o DEL (character 127) is displayed as ^?.
o 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 nota-
tion, or are displayed as themselves. In the latter
case, the values may not be printable; this follows
the X/Open specification.
o Values above 256 may be the names of the names of
function keys.
o Otherwise (if there is no corresponding name) the
function returns null, to denote an error. X/Open al-
so lists an "UNKNOWN KEY" return value, which some im-
plementations return rather than null.
The corresponding key_name returns a character string cor-
responding to the wide-character value w. The two func-
tions do not return the same set of strings; the latter
returns null where the former would display a meta charac-
ter.
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 environ-
ment variables when determining the screen size.
o 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.
o Then it asks for the screen size via operating system
calls. If successful, it overrides the values from
the terminal database.
o Finally (unless use_env was called with FALSE parame-
ter), ncurses examines the LINES or COLUMNS environ-
ment variables, using a value in those to override the
results from the operating system or terminal data-
base.
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 computa-
tion of screen size as follows:
o checks if the LINES and COLUMNS environment variables
are set to a number greater than zero.
o for each, ncurses updates the corresponding environ-
ment variable with the value that it has obtained via
operating system call or from the terminal database.
o ncurses re-fetches the value of the environment vari-
ables 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 over-
ridden 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, us-
es 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
(or pad) win into the file to which filep points. This
information can be later retrieved using the getwin func-
tion.
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:
o the data written is a copy of the WINDOW structure,
and its associated character cells. The format dif-
fers between the wide-character (ncursesw) and non-
wide (ncurses) libraries. You can transfer data be-
tween the two, however.
o the retrieved window is always created as a top-level
window (or pad), rather than a subwindow.
o 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.
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.
Except for flushinp, routines that return an integer re-
turn ERR upon failure and OK (SVr4 specifies only "an in-
teger 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 im-
plementation
flushinp
returns an error if the terminal was not initial-
ized.
meta returns an error if the terminal was not initial-
ized.
putwin
returns an error if the associated fwrite calls
return an error.
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 keyname function may return the names of user-defined
string capabilities which are defined in the terminfo en-
try via the -x option of tic. This implementation auto-
matically 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 li-
brary.
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.
The putwin and getwin functions have several issues with
portability:
o 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) incorpo-
rated into SVr4. Oddly, there are no such functions
in the 4.3BSD curses sources.
o Most implementations simply dump the binary WINDOW
structure to the file. These include SVr4 curses,
NetBSD and PDCurses, as well as older ncurses ver-
sions. 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. Howev-
er, reading from a file written using mixed schemes
may not be successful.
The XSI Curses standard, Issue 4 describes these func-
tions. It states that unctrl and wunctrl will return a
null pointer if unsuccessful, but does not define any er-
ror conditions. This implementation checks for three cas-
es:
o the parameter is a 7-bit US-ASCII code. This is the
case that X/Open Curses documented.
o the parameter is in the range 128-159, i.e., a C1 con-
trol 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 implementa-
tion permits that, and returns the "~@", etc., values
in that case.
o 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 print-
able. This implementation uses 8 bits but does not modify
the string to reflect locale. The use_legacy_coding func-
tion 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.
legacy_coding(3x), curses(3x), curs_initscr(3x), curs_ker-
nel(3x), curs_scr_dump(3x), curs_variables(3x), lega-
cy_coding(3x).
curs_util(3x)