# 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>

           const char *unctrl(chtype c);
           wchar_t *wunctrl(cchar_t *c);

           const char *keyname(int c);
           const 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.  Calling filter causes these changes in initialization:

           o   LINES is set to 1;

           o   the  capabilities  clear,  cud1,  cud, cup, cuu1, cuu, vpa are dis-
               abled;

           o   the capability ed is disabled if bce is set;

           o   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 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 file-format

           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(3x)  has  been  called with a 2 parameter, unctrl
               returns the parameter, i.e., a one-character string with the param-
               eter  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(3x) 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_cod-
           ing(3x) and meta(3x) 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 initializ-
           ing curses), this implementation returns strings "M-^@", "M-^A", etc.

           X/Open Curses documents unctrl as declared in <unctrl.h>, which ncurses
           does.  However, ncurses' <curses.h> includes <unctrl.h>,  matching  the
           behavior of SVr4 curses.  Other implementations may not do that.

### 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

           curses(3x),   curs_initscr(3x),    curs_inopts(3x),    curs_kernel(3x),
           curs_scr_dump(3x),  curs_sp_funcs(3x),  curs_variables(3x), legacy_cod-
           ing(3x).

                                                                     curs_util(3x)