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

   ·   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 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
   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 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
       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

   ·   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

           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


   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 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
   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 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

   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 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.


   legacy_coding(3NCURSES),     ncurses(3NCURSES),      initscr(3NCURSES),
   kernel(3NCURSES),    scr_dump(3NCURSES),    curses_variables(3NCURSES),



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