# curs_util 3x

    curs_util(3x)                                             curs_util(3x)

## 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

           The  unctrl  routine returns a character string which is a
           printable representation of the character c, ignoring  at-
           tributes.   Control characters are displayed in the ^X no-
           tation.  Printing characters are  displayed  as  is.   The
           corresponding  wunctrl  returns a printable representation
           of a wide character.

           The keyname routine returns a character string correspond-
           ing to the key c:

              o   Printable  characters  are displayed as themselves,
                  e.g., a one-character string containing the key.

              o   Control characters are displayed in  the  ^X  nota-
                  tion.

              o   DEL (character 127) is displayed as ^?.

              o   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.

              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 implementations return rather than null.

           The corresponding key_name returns a character string cor-
           responding  to  the wide-character value w.  The two func-
           tions do not return the same set of  strings;  the  latter
           returns null where the former would display a meta charac-
           ter.

           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 environ-
           ment 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 overrides the values from
               the terminal database.

           o   Finally (unless use_env was called with FALSE  parame-
               ter),  ncurses  examines the LINES or COLUMNS environ-
               ment variables, using a value in those to override the
               results  from  the  operating system or terminal data-
               base.

               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 computa-
           tion of screen size as follows:

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

           o   for  each,  ncurses updates the corresponding environ-
               ment 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 vari-
               ables 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
                                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.

           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.

## RETURN VALUE

           Except for flushinp, routines that return an  integer  re-
           turn  ERR upon failure and OK (SVr4 specifies only "an in-
           teger 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  im-
           plementation

              flushinp
                   returns  an error if the terminal was not initial-
                   ized.

              meta returns an error if the terminal was not  initial-
                   ized.

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

## PORTABILITY

           The XSI Curses standard, Issue  4  describes  these  func-
           tions.   It  states  that unctrl and wunctrl will return a
           null pointer if unsuccessful, but does not define any  er-
           ror conditions.  This implementation checks for three cas-
           es:

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

              o   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.

              o   parameter  values outside the 0 to 255 range.  unc-
                  trl 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 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 print-
           able.  This implementation uses 8 bits but does not modify
           the string to reflect locale.  The use_legacy_coding func-
           tion 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 en-
           try via the -x option of tic.  This  implementation  auto-
           matically  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 li-
           brary.

           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.

## SEE ALSO

           legacy_coding(3x), curses(3x), curs_initscr(3x), curs_ker-
           nel(3x),   curs_scr_dump(3x),   curs_variables(3x),  lega-
           cy_coding(3x).

                                                              curs_util(3x)