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$Id: curs_initscr.3x,v 1.69 2024/04/20 21:24:19 tom Exp $
#include <curses.h>WINDOW *initscr(void); int endwin(void);
bool isendwin(void);
SCREEN *newterm(const char *type, FILE *outf, FILE *inf); SCREEN *set_term(SCREEN *new); void delscreen(SCREEN* sp);
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.
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 .bP the type of the terminal to be used in place of $TERM, .bP an output stream connected to the terminal, and .bP an input stream connected to the terminal
If the type parameter is NULL, $TERM will be used.
The file descriptor of the output stream is passed to setupterm(3X), which returns a pointer to a \%TERMINAL structure. newterm's return value holds a pointer to the \%TERMINAL structure.
A program should always call endwin before exiting or escaping from curses mode temporarily. This routine .bP resets colors to correspond with the default color pair 0, .bP moves the cursor to the lower left-hand corner of the screen, .bP clears the remainder of the line so that it uses the default colors, .bP sets the cursor to normal visibility (see curs_set(3X)), .bP stops cursor-addressing mode using the exit_ca_mode terminal capability, .bP 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.
Routines that return pointers always return NULL on error.
X/Open defines no error conditions. In this implementation .bP endwin returns an error if
.bP the terminal was not initialized, or .bP endwin is called more than once without updating the screen, or .bP reset_shell_mode(3X) returns an error.
Old versions of curses, e.g., BSD 4.4, would return 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 X/Open Curses.
Calling endwin does not dispose of the memory allocated in initscr or newterm. Deleting a SCREEN provides a way to do this: .bP X/Open Curses does not say what happens to \%WINDOWs when delscreen \*(``frees storage associated with the SCREEN\*('' nor does the SVr4 documentation help, adding that it should be called after endwin if a SCREEN is no longer needed. .bP However, \%WINDOWs are implicitly associated with a SCREEN. so that it is reasonable to expect delscreen to deal with these. .bP SVr4 curses deletes the standard \%WINDOW structures stdscr and curscr as well as a work area newscr. SVr4 curses ignores other windows. .bP Since version 4.0 (1996), \%ncurses has maintained a list of all windows for each screen, using that information to delete those windows when delscreen is called. .bP NetBSD copied this feature of \%ncurses in 2001. PDCurses follows the SVr4 model, deleting only the standard \%WINDOW structures.
For example .bP NetBSD's baudrate(3X) function uses the descriptor in \%TERMINAL. \%ncurses and SVr4 use the descriptor in SCREEN. .bP NetBSD and \%ncurses use the descriptor in \%TERMINAL for terminal I/O modes, e.g., def_shell_mode(3X), def_prog_mode(3X). SVr4 curses uses the descriptor in SCREEN.
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:
5 SIGINT The handler attempts to clean up the screen on exit. Although it usually works as expected, there are limitations:
.bP Walking the SCREEN list is unsafe, since all list management is done without any signal blocking. .bP On systems which have REENTRANT turned on, set_term uses functions which could deadlock or misbehave in other ways. .bP endwin calls other functions, many of which use \%stdio(3) or other library functions which are clearly unsafe.
5 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).
5 SIGTSTP This handles the stop signal, used in job control. When resuming the process, this implementation discards pending input with \%flushinp(3X), and repaints the screen assuming that it has been completely altered. It also updates the saved terminal modes with \%def_shell_mode(3X).
5 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(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.