NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | PORTABILITY | SEE ALSO | COLOPHON

curs_util(3X)                                                  curs_util(3X)

NAME         top

       delay_output, filter, flushinp, getwin, key_name, keyname, nofilter,
       putwin, unctrl, use_env, use_tioctl, wunctrl - miscellaneous curses
       utility routines

SYNOPSIS         top

       #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         top

   unctrl
       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.

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

       ·   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(3X) 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.

   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
       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,

   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:

       ·   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
                                 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 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
       caveats:

       ·   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.

   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 specified, 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         top

       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
               error.

PORTABILITY         top

   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
       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(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
       conditioned using NCURSES_VERSION.

   putwin/getwin
       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.

   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:

       ·   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 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
       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(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         top

       legacy_coding(3X), curses(3X), curs_initscr(3X), curs_inopts(3X),
       curs_kernel(3X), curs_scr_dump(3X), curs_sp_funcs(3X),
       curs_variables(3X), legacy_coding(3X).

COLOPHON         top

       This page is part of the ncurses (new curses) project.  Information
       about the project can be found at 
       ⟨https://www.gnu.org/software/ncurses/ncurses.html⟩.  If you have a
       bug report for this manual page, send it to
       bug-ncurses-request@gnu.org.  This page was obtained from the
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       ⟨git://ncurses.scripts.mit.edu/ncurses.git⟩ on 2017-09-15.  If you
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       COLOPHON (which is not part of the original manual page), send a mail
       to man-pages@man7.org

                                                               curs_util(3X)