Ubuntu Manpage: delay_output, filter, flushinp, getwin, key_name, keyname, nofilter, putwin, unctrl, use_env, use

Provided by: ncurses-doc_6.0+20160213-1ubuntu1_all

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

unctrl
The unctrl routine returns a character string which is a printable representation of the character c, ig‐
noring attributes. Control characters are displayed in the ^X notation. Printing characters are dis‐
played 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 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 dis‐
play a meta character.

filter/nofilter
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 dis‐
abled; 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 fil‐
ter routine modifies the in-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 com‐
pute 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 envi‐
ronment variables, using a value in those to override the results from the operating system or termi‐
nal database.

Ncurses 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:

• 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 vari‐
ables 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.

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 da‐
ta 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 ms millisecond pause in output. This routine should not be used ex‐
tensively because padding characters are used rather than a CPU pause. If no padding character is speci‐
fied, 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 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

   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 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 condi‐
       tioned 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  re‐
       turn  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 imple‐
           mentation 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 conven‐
       tions.  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 implemen‐
       tation uses 8 bits but does not modify the string to reflect locale.  The use_legacy_coding function  al‐
       lows 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  curs‐
       es), this implementation returns strings “M-^@”, “M-^A”, etc.

NAME

SYNOPSIS

DESCRIPTION

RETURN VALUE

PORTABILITY

SEE ALSO