nofilter man page on Oracle

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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 rep‐
       resentation of the character c, ignoring attributes.   Control  charac‐
       ters  are  displayed  in the ^X notation.  Printing characters are dis‐
       played as is.  The corresponding wunctrl returns a printable  represen‐
       tation of a wide character.

       The keyname routine returns a character string corresponding to the key

	  ·   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 pa‐
	      rameter),	 shown	in the M-X notation, or are displayed as them‐
	      selves.  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 re‐
	      turns null, to denote an error.  X/Open also lists  an  "UNKNOWN
	      KEY" return value, which some implementations return rather than

       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 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	 modi‐
       fies  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 un‐
	   less 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 environment variables, using a	 value
	   in  those to override the results from the operating system or ter‐
	   minal database.

	   Ncurses also updates the screen size in response to	SIGWINCH,  un‐
	   less 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 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 speci‐
       fied, 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 er‐

       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 has been called with a 2 parameter, unctrl
	      returns the parameter, i.e., a one-character string with the pa‐
	      rameter  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 be‐
	      fore 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  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 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 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

       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 capa‐
       bilities 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.

       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.

       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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