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curs_initscr(3X)					      curs_initscr(3X)

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(const 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 curs-
       es 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  re-
       turned 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	termi-
       nal.  It	returns	a variable of type SCREEN * which should be saved as a
       reference to that terminal.  newterm's arguments	are

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

       o   a file pointer for output to	the terminal, and

       o   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

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

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

       o   clears  the	remainder of the line so that it uses the default col-
	   ors,

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

       o   stops cursor-addressing mode	using the exit_ca_mode terminal	 capa-
	   bility,

       o   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	previ-
       ous  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 com-
       pletion.

       Routines	that return pointers always return NULL	on error.

       X/Open defines no error conditions.  In this implementation

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

       o   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.

       o   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:

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

       o   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 "un-
       known", 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  disposi-
	    tion 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  li-
       brary:

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

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

	    o	On systems which have REENTRANT	turned on, set_term uses func-
		tions which could deadlock or misbehave	in other ways.

	    o	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)	 vari-
	    able  which	 is  later  tested in wgetch (see curs_getch(3X)).  If
	    keypad has been enabled for	the corresponding window,  wgetch  re-
	    turns  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
       curses(3X),  curs_kernel(3X), curs_refresh(3X), curs_slk(3X), curs_ter-
       minfo(3X), curs_util(3X), curs_variables(3X).

							      curs_initscr(3X)

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

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