# 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

### unctrl

           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.

### keyname/key_name

           The keyname routine returns a character string corresponding to the key
           c:

           o   Printable characters are displayed as themselves, e.g., a one-char-
               acter string containing 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 initialized, or if meta(3x) has been called with a TRUE param-
               eter),  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"  re-
               turn 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.

### 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  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.

### use_env

           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.

           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  un-
               less 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  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,

### 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:

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

           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 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.

### 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 re-
           trieved 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:

           o   the data written is a copy of the WINDOW structure, and its associ-
               ated character cells.  The format differs between the  wide-charac-
               ter  (ncursesw) and non-wide (ncurses) libraries.  You can transfer
               data between the two, however.

           o   the retrieved window is always created as a  top-level  window  (or
               pad), rather than a subwindow.

           o   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 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.

### 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.

              putwin
                   returns an error if the associated fwrite calls return  an  er-
                   ror.

## 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 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(3x) 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:

           o   The files written and read by these functions  use  an  implementa-
               tion-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.

           o   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 return a null pointer if unsuccessful, but
           does  not  define any error conditions.  This implementation checks for
           three cases:

           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  re-
               turns  the parameter, i.e., a one-character string with the parame-
               ter 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 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
           unctrl.

           Likewise, the meta(3x) 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.

### use_env/use_tioctl

           If ncurses is configured to provide  the  sp-functions  extension,  the
           state  of  use_env  and  use_tioctl may be updated before creating each
           screen rather than once  only  (curs_sp_funcs(3x)).   This  feature  of
           use_env is not provided by other implementation of curses.

## SEE ALSO

           legacy_coding(3x),   curses(3x),   curs_initscr(3x),   curs_inopts(3x),
           curs_kernel(3x),   curs_scr_dump(3x),   curs_sp_funcs(3x),   curs_vari-
           ables(3x), legacy_coding(3x).

                                                                     curs_util(3x)