curs_util 3x

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

       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.


       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.

       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,


       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
           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 (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

       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.


       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.

               returns an error if the associated fwrite calls return  an  er-



       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 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.


       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.


       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.


       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

       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(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.


       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.


       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).