curses процедуры инициализации экрана и манипуляции (curses screen initialization and manipulation routines)
Имя (Name)
initscr, newterm, endwin, isendwin, set_term, delscreen - curses
screen initialization and manipulation routines
Синопсис (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);
Описание (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.
Возвращаемое значение (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.
Портативность (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.
Смотри также (See also)
curses(3X), curs_kernel(3X), curs_refresh(3X), curs_slk(3X),
curs_terminfo(3X), curs_util(3X), curs_variables(3X).
