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curs_util(3)                                                      curs_util(3)


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


       #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);


       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.

       The keyname routine returns a character string corresponding to the key

       o   Printable characters are displayed as themselves, e.g., a one-
           character 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
           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 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

       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 disabled;

       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.

       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.

       o   Normally ncurses looks first at the terminal database for the screen

           If use_env was called with FALSE for parameter, it stops here unless
           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 terminal

           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 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
                                   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
            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
       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:

       o   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.

       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 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.


       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 error.


       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
       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

       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 file-format
       The putwin and getwin functions have several issues with portability:

       o   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.

       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(3X) 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.

       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
       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(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_coding(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 initializing 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.

       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.


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


ncurses 6.4 - Generated Tue Jan 3 19:44:50 CST 2023
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