delay_output, filter, flushinp, getwin,
key_name, keyname, nofilter, putwin,
unctrl, use_env, use_tioctl, wunctrl -
miscellaneous curses utility routines
#include <ncurses/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 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 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(3X) 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. 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.
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.
- 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 (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.
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 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.
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 entry via the -x option
of gtic. 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.
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:
- •
- 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.
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 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(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'
<curses.h> includes <unctrl.h>, matching the
behavior of SVr4 curses. Other implementations may not do that.
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 (curs_sp_funcs(3X)). This feature
of use_env is not provided by other implementation of curses.