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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	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:

	  o   Printable characters are displayed as themselves, e.g., a one-character string con-
	      taining 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  initial-
	      ized, 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  print-
	      able; 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 also lists an "UNKNOWN KEY" return value, which some  implementa-
	      tions 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 ef-
       fect 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 call-
       er 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

       The use_env routine, if used, should be called before initscr or newterm are  called  (be-
       cause  those  compute  the  screen  size).  It modifies the way ncurses treats environment
       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 over-
	   rides the values from the terminal database.

       o   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 argu-
       ment, ncurses modifies the last step in its computation of screen size as follows:

       o   checks if the LINES and COLUMNS environment variables are set to a number greater than

       o   for each, ncurses updates the corresponding environment 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 variables so that it is still the en-
	   vironment 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
		    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
		    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.

       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

	       returns an error if the terminal was not initialized.

	  meta returns an error if the terminal was not initialized.

	       returns an error if the associated fwrite calls return an error.

       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 condi-
       tions.  This implementation checks for three cases:

	  o   the parameter is a 7-bit US-ASCII code.  This is the case that X/Open Curses  docu-

	  o   the parameter is in the range 128-159, i.e., a C1 control code.  If use_legacy_cod-
	      ing 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.

	  o   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  de-
       scription  here	is  adapted  from the XSI Curses standard (which erroneously fails to de-
       scribe 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 im-
       plementations 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  de-
       scription 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.

       legacy_coding(3X),   curses(3X),   curs_initscr(3X),  curs_kernel(3X),  curs_scr_dump(3X),
       curs_variables(3X), legacy_coding(3X).

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