NAME

       initscr, newterm, endwin, isendwin, set_term, delscreen - curses screen initialization and manipulation
       routines

SYNOPSIS

       #include <curses.h>

       WINDOW *initscr(void);
       int endwin(void);
       bool isendwin(void);
       SCREEN *newterm(char *type, FILE *outfd, FILE *infd);
       SCREEN *set_term(SCREEN *new);
       void delscreen(SCREEN* sp);

DESCRIPTION

   initscr
       initscr is normally the first curses routine to call when initializing a program.  A few special routines
       sometimes  need  to  be  called  before  it;  these  are  slk_init(3X), filter, ripoffline, use_env.  For
       multiple-terminal applications, newterm may be called before initscr.

       The initscr code determines the terminal type and initializes all curses data structures.   initscr  also
       causes the first call to refresh(3X) to clear the screen.  If errors occur, initscr writes an appropriate
       error message to standard error and exits; otherwise, a pointer is returned to stdscr.

   newterm
       A program that outputs to more than one terminal should use the newterm routine for each terminal instead
       of  initscr.   A program that needs to inspect capabilities, so it can continue to run in a line-oriented
       mode if the terminal cannot support a screen-oriented program,  would  also  use  newterm.   The  routine
       newterm  should be called once for each terminal.  It returns a variable of type SCREEN * which should be
       saved as a reference to that terminal.  newterm's arguments are

       •   the type of the terminal to be used in place of $TERM,

       •   a file pointer for output to the terminal, and

       •   another file pointer for input from the terminal

       If the type parameter is NULL, $TERM will be used.

   endwin
       The program must also call endwin for each terminal being used before exiting from curses.  If newterm is
       called  more  than  once  for  the same terminal, the first terminal referred to must be the last one for
       which endwin is called.

       A program should always call endwin before exiting  or  escaping  from  curses  mode  temporarily.   This
       routine

       •   resets colors to correspond with the default color pair 0,

       •   moves the cursor to the lower left-hand corner of the screen,

       •   clears the remainder of the line so that it uses the default colors,

       •   sets the cursor to normal visibility (see curs_set(3X)),

       •   stops cursor-addressing mode using the exit_ca_mode terminal capability,

       •   restores tty modes (see reset_shell_mode(3X)).

       Calling refresh(3X) or doupdate(3X) after a temporary escape causes the program to resume visual mode.

   isendwin
       The isendwin routine returns TRUE if endwin has been called without any subsequent calls to wrefresh, and
       FALSE otherwise.

   set_term
       The set_term routine is used to switch between different terminals.  The screen reference new becomes the
       new  current terminal.  The previous terminal is returned by the routine.  This is the only routine which
       manipulates SCREEN pointers; all other routines affect only the current terminal.

   delscreen
       The delscreen routine frees storage associated with the SCREEN data structure.  The endwin  routine  does
       not do this, so delscreen should be called after endwin if a particular SCREEN is no longer needed.

RETURN VALUE

       endwin returns the integer ERR upon failure and OK upon successful completion.

       Routines that return pointers always return NULL on error.

       X/Open defines no error conditions.  In this implementation

       •   endwin returns an error if the terminal was not initialized.

       •   newterm  returns  an  error if it cannot allocate the data structures for the screen, or for the top-
           level windows within the screen, i.e., curscr, newscr, or stdscr.

       •   set_term returns no error.

PORTABILITY

       These functions were described in the XSI Curses standard, Issue 4.  As of 2015, the current document  is
       X/Open Curses, Issue 7.

   Differences
       X/Open specifies that portable applications must not call initscr more than once:

       •   The  portable  way  to  use initscr is once only, using refresh (see curs_refresh(3X)) to restore the
           screen after endwin.

       •   This implementation allows using initscr after endwin.

       Old versions of curses, e.g., BSD 4.4, may have returned a null pointer from initscr  when  an  error  is
       detected,  rather  than  exiting.   It  is safe but redundant to check the return value of initscr in XSI
       Curses.

   Unset TERM Variable
       If the TERM variable is missing or empty, initscr uses the value “unknown”, which normally corresponds to
       a  terminal  entry  with  the  generic  (gn)  capability.  Generic entries are detected by setupterm (see
       curs_terminfo(3X)) and cannot be used for full-screen operation.   Other  implementations  may  handle  a
       missing/empty TERM variable differently.

   Signal Handlers
       Quoting from X/Open Curses, section 3.1.1:

            Curses  implementations  may provide for special handling of the SIGINT, SIGQUIT and SIGTSTP signals
            if their disposition is SIG_DFL at the time initscr is called ...

            Any special handling for these signals may remain in effect for the life of the process or until the
            process changes the disposition of the signal.

            None of the Curses functions are required to be safe with respect to signals ...

       This  implementation  establishes  signal  handlers  during  initialization,  e.g.,  initscr  or newterm.
       Applications which must handle these signals should set up the corresponding handlers after  initializing
       the library:

       SIGINT
            The  handler  attempts  to cleanup the screen on exit.  Although it usually works as expected, there
            are limitations:

            •   Walking the SCREEN list is unsafe,  since  all  list  management  is  done  without  any  signal
                blocking.

            •   On  systems  which  have  REENTRANT  turned  on, set_term uses functions which could deadlock or
                misbehave in other ways.

            •   endwin calls other functions, many of which use stdio  or  other  library  functions  which  are
                clearly unsafe.

       SIGTERM
            This  uses  the  same  handler  as SIGINT, with the same limitations.  It is not mentioned in X/Open
            Curses, but is more suitable for this purpose than SIGQUIT (which is used in debugging).

       SIGTSTP
            This handles the stop signal, used in job control.  When resuming the process,  this  implementation
            discards pending input with flushinput (see curs_util(3X)), and repaints the screen assuming that it
            has been completely altered.  It also updates the saved  terminal  modes  with  def_shell_mode  (see
            curs_kernel(3X)).

       SIGWINCH
            This handles the window-size changes which were ignored in the standardization efforts.  The handler
            sets a (signal-safe) variable which is later tested in wgetch (see curs_getch(3X)).  If  keypad  has
            been  enabled  for  the corresponding window, wgetch returns the key symbol KEY_RESIZE.  At the same
            time, wgetch calls resizeterm to adjust the standard screen stdscr, and update other  data  such  as
            LINES and COLS.

SEE ALSO

       ncurses(3NCURSES),     kernel(3NCURSES),     refresh(3NCURSES),     slk(3NCURSES),    terminfo(3NCURSES),
       util(3NCURSES), curses_variables(3NCURSES).

                                                                                               initscr(3NCURSES)