1curs_initscr(3X) curs_initscr(3X)
2
6 initscr, newterm, endwin, isendwin, set_term, delscreen - curses screen
7 initialization and manipulation routines
8
10 #include <curses.h>
11 WINDOW *initscr(void);
13 int endwin(void);
14 bool isendwin(void);
16 SCREEN *newterm(const char *type, FILE *outfd, FILE *infd);
18 SCREEN *set_term(SCREEN *new);
19 void delscreen(SCREEN* sp);
20
22 initscr
23 initscr is normally the first curses routine to call when initializing
24 a program. A few special routines sometimes need to be called before
25 it; these are slk_init(3X), filter, ripoffline, use_env. For multiple-
26 terminal applications, newterm may be called before initscr.
27 The initscr code determines the terminal type and initializes all curs‐
29 es data structures. initscr also causes the first call to refresh(3X)
30 to clear the screen. If errors occur, initscr writes an appropriate
31 error message to standard error and exits; otherwise, a pointer is re‐
32 turned to stdscr.
33 newterm
35 A program that outputs to more than one terminal should use the newterm
36 routine for each terminal instead of initscr. A program that needs to
37 inspect capabilities, so it can continue to run in a line-oriented mode
38 if the terminal cannot support a screen-oriented program, would also
39 use newterm. The routine newterm should be called once for each termi‐
40 nal. It returns a variable of type SCREEN * which should be saved as a
41 reference to that terminal. newterm's arguments are
42 • the type of the terminal to be used in place of $TERM,
44 • a file pointer for output to the terminal, and
46 • another file pointer for input from the terminal
48 If the type parameter is NULL, $TERM will be used.
50 endwin
52 The program must also call endwin for each terminal being used before
53 exiting from curses. If newterm is called more than once for the same
54 terminal, the first terminal referred to must be the last one for which
55 endwin is called.
56 A program should always call endwin before exiting or escaping from
58 curses mode temporarily. This routine
59 • resets colors to correspond with the default color pair 0,
61 • moves the cursor to the lower left-hand corner of the screen,
63 • clears the remainder of the line so that it uses the default col‐
65 ors,
66 • sets the cursor to normal visibility (see curs_set(3X)),
68 • stops cursor-addressing mode using the exit_ca_mode terminal capa‐
70 bility,
71 • restores tty modes (see reset_shell_mode(3X)).
73 Calling refresh(3X) or doupdate(3X) after a temporary escape causes the
75 program to resume visual mode.
76 isendwin
78 The isendwin routine returns TRUE if endwin has been called without any
79 subsequent calls to wrefresh, and FALSE otherwise.
80 set_term
82 The set_term routine is used to switch between different terminals.
83 The screen reference new becomes the new current terminal. The previ‐
84 ous terminal is returned by the routine. This is the only routine
85 which manipulates SCREEN pointers; all other routines affect only the
86 current terminal.
87 delscreen
89 The delscreen routine frees storage associated with the SCREEN data
90 structure. The endwin routine does not do this, so delscreen should be
91 called after endwin if a particular SCREEN is no longer needed.
92
94 endwin returns the integer ERR upon failure and OK upon successful com‐
95 pletion.
96 Routines that return pointers always return NULL on error.
98 X/Open defines no error conditions. In this implementation
100 • endwin returns an error if the terminal was not initialized.
102 • newterm returns an error if it cannot allocate the data structures
104 for the screen, or for the top-level windows within the screen,
105 i.e., curscr, newscr, or stdscr.
106 • set_term returns no error.
108
110 These functions were described in the XSI Curses standard, Issue 4. As
111 of 2015, the current document is X/Open Curses, Issue 7.
112 Differences
114 X/Open specifies that portable applications must not call initscr more
115 than once:
116 • The portable way to use initscr is once only, using refresh (see
118 curs_refresh(3X)) to restore the screen after endwin.
119 • This implementation allows using initscr after endwin.
121 Old versions of curses, e.g., BSD 4.4, may have returned a null pointer
123 from initscr when an error is detected, rather than exiting. It is
124 safe but redundant to check the return value of initscr in XSI Curses.
125 Unset TERM Variable
127 If the TERM variable is missing or empty, initscr uses the value “un‐
128 known”, which normally corresponds to a terminal entry with the generic
129 (gn) capability. Generic entries are detected by setupterm (see
130 curs_terminfo(3X)) and cannot be used for full-screen operation. Other
131 implementations may handle a missing/empty TERM variable differently.
132 Signal Handlers
134 Quoting from X/Open Curses, section 3.1.1:
135 Curses implementations may provide for special handling of the
137 SIGINT, SIGQUIT and SIGTSTP signals if their disposition is
138 SIG_DFL at the time initscr is called ...
139 Any special handling for these signals may remain in effect for
141 the life of the process or until the process changes the
142 disposition of the signal.
143 None of the Curses functions are required to be safe with respect
145 to signals ...
146 This implementation establishes signal handlers during initialization,
148 e.g., initscr or newterm. Applications which must handle these signals
149 should set up the corresponding handlers after initializing the li‐
150 brary:
151 SIGINT
153 The handler attempts to cleanup the screen on exit. Although it
154 usually works as expected, there are limitations:
155 • Walking the SCREEN list is unsafe, since all list management
157 is done without any signal blocking.
158 • On systems which have REENTRANT turned on, set_term uses func‐
160 tions which could deadlock or misbehave in other ways.
161 • endwin calls other functions, many of which use stdio or other
163 library functions which are clearly unsafe.
164 SIGTERM
166 This uses the same handler as SIGINT, with the same limitations.
167 It is not mentioned in X/Open Curses, but is more suitable for
168 this purpose than SIGQUIT (which is used in debugging).
169 SIGTSTP
171 This handles the stop signal, used in job control. When resuming
172 the process, this implementation discards pending input with
173 flushinput (see curs_util(3X)), and repaints the screen assuming
174 that it has been completely altered. It also updates the saved
175 terminal modes with def_shell_mode (see curs_kernel(3X)).
176 SIGWINCH
178 This handles the window-size changes which were ignored in the
179 standardization efforts. The handler sets a (signal-safe) vari‐
180 able which is later tested in wgetch (see curs_getch(3X)). If
181 keypad has been enabled for the corresponding window, wgetch re‐
182 turns the key symbol KEY_RESIZE. At the same time, wgetch calls
183 resizeterm to adjust the standard screen stdscr, and update other
184 data such as LINES and COLS.
185
187 curses(3X), curs_kernel(3X), curs_refresh(3X), curs_slk(3X), curs_ter‐
188 minfo(3X), curs_util(3X), curs_variables(3X).
189 curs_initscr(3X)