ncurses 6.2 - patch 20200425
[ncurses.git] / doc / html / man / curs_initscr.3x.html
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30   * @Id: curs_initscr.3x,v 1.32 2020/02/02 23:34:34 tom Exp @
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42 <H1 class="no-header">curs_initscr 3x</H1>
43 <PRE>
44 <STRONG><A HREF="curs_initscr.3x.html">curs_initscr(3x)</A></STRONG>                                              <STRONG><A HREF="curs_initscr.3x.html">curs_initscr(3x)</A></STRONG>
45
46
47
48
49 </PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
50        <STRONG>initscr</STRONG>, <STRONG>newterm</STRONG>, <STRONG>endwin</STRONG>, <STRONG>isendwin</STRONG>, <STRONG>set_term</STRONG>, <STRONG>delscreen</STRONG> - <STRONG>curses</STRONG> screen
51        initialization and manipulation routines
52
53
54 </PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
55        <STRONG>#include</STRONG> <STRONG>&lt;curses.h&gt;</STRONG>
56
57        <STRONG>WINDOW</STRONG> <STRONG>*initscr(void);</STRONG>
58        <STRONG>int</STRONG> <STRONG>endwin(void);</STRONG>
59        <STRONG>bool</STRONG> <STRONG>isendwin(void);</STRONG>
60        <STRONG>SCREEN</STRONG> <STRONG>*newterm(const</STRONG> <STRONG>char</STRONG> <STRONG>*</STRONG><EM>type</EM><STRONG>,</STRONG> <STRONG>FILE</STRONG> <STRONG>*</STRONG><EM>outfd</EM><STRONG>,</STRONG> <STRONG>FILE</STRONG> <STRONG>*</STRONG><EM>infd</EM><STRONG>);</STRONG>
61        <STRONG>SCREEN</STRONG> <STRONG>*set_term(SCREEN</STRONG> <STRONG>*</STRONG><EM>new</EM><STRONG>);</STRONG>
62        <STRONG>void</STRONG> <STRONG>delscreen(SCREEN*</STRONG> <EM>sp</EM><STRONG>);</STRONG>
63
64
65 </PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
66
67 </PRE><H3><a name="h3-initscr">initscr</a></H3><PRE>
68        <STRONG>initscr</STRONG> is normally the first <STRONG>curses</STRONG> routine to call when  initializing
69        a  program.   A few special routines sometimes need to be called before
70        it; these are <STRONG><A HREF="curs_slk.3x.html">slk_init(3x)</A></STRONG>, <STRONG>filter</STRONG>, <STRONG>ripoffline</STRONG>, <STRONG>use_env</STRONG>.  For multiple-
71        terminal applications, <STRONG>newterm</STRONG> may be called before <STRONG>initscr</STRONG>.
72
73        The initscr code determines the terminal type and initializes all <STRONG>curs-</STRONG>
74        <STRONG>es</STRONG> data structures.  <STRONG>initscr</STRONG> also causes the first call to  <STRONG><A HREF="curscurs_refresh.3x.html">refresh(3x)</A></STRONG>
75        to  clear  the  screen.  If errors occur, <STRONG>initscr</STRONG> writes an appropriate
76        error message to standard error and exits; otherwise, a pointer is  re-
77        turned to <STRONG>stdscr</STRONG>.
78
79
80 </PRE><H3><a name="h3-newterm">newterm</a></H3><PRE>
81        A program that outputs to more than one terminal should use the <STRONG>newterm</STRONG>
82        routine for each terminal instead of <STRONG>initscr</STRONG>.  A program that needs  to
83        inspect capabilities, so it can continue to run in a line-oriented mode
84        if the terminal cannot support a screen-oriented  program,  would  also
85        use <STRONG>newterm</STRONG>.  The routine <STRONG>newterm</STRONG> should be called once for each termi-
86        nal.  It returns a variable of type <STRONG>SCREEN</STRONG> <STRONG>*</STRONG> which should be saved as a
87        reference to that terminal.  <STRONG>newterm</STRONG>'s arguments are
88
89        <STRONG>o</STRONG>   the <EM>type</EM> of the terminal to be used in place of <STRONG>$TERM</STRONG>,
90
91        <STRONG>o</STRONG>   a file pointer for output to the terminal, and
92
93        <STRONG>o</STRONG>   another file pointer for input from the terminal
94
95        If the <EM>type</EM> parameter is <STRONG>NULL</STRONG>, <STRONG>$TERM</STRONG> will be used.
96
97
98 </PRE><H3><a name="h3-endwin">endwin</a></H3><PRE>
99        The  program  must also call <STRONG>endwin</STRONG> for each terminal being used before
100        exiting from <STRONG>curses</STRONG>.  If <STRONG>newterm</STRONG> is called more than once for the  same
101        terminal, the first terminal referred to must be the last one for which
102        <STRONG>endwin</STRONG> is called.
103
104        A program should always call <STRONG>endwin</STRONG> before  exiting  or  escaping  from
105        <STRONG>curses</STRONG> mode temporarily.  This routine
106
107        <STRONG>o</STRONG>   resets colors to correspond with the default color pair 0,
108
109        <STRONG>o</STRONG>   moves the cursor to the lower left-hand corner of the screen,
110
111        <STRONG>o</STRONG>   clears  the  remainder of the line so that it uses the default col-
112            ors,
113
114        <STRONG>o</STRONG>   sets the cursor to normal visibility (see <STRONG><A HREF="curs_kernel.3x.html">curs_set(3x)</A></STRONG>),
115
116        <STRONG>o</STRONG>   stops cursor-addressing mode using the <EM>exit</EM><STRONG>_</STRONG><EM>ca</EM><STRONG>_</STRONG><EM>mode</EM> terminal  capa-
117            bility,
118
119        <STRONG>o</STRONG>   restores tty modes (see <STRONG><A HREF="curs_kernel.3x.html">reset_shell_mode(3x)</A></STRONG>).
120
121        Calling <STRONG><A HREF="curs_refresh.3x.html">refresh(3x)</A></STRONG> or <STRONG><A HREF="curs_refresh.3x.html">doupdate(3x)</A></STRONG> after a temporary escape causes the
122        program to resume visual mode.
123
124
125 </PRE><H3><a name="h3-isendwin">isendwin</a></H3><PRE>
126        The <STRONG>isendwin</STRONG> routine returns <STRONG>TRUE</STRONG> if <STRONG>endwin</STRONG> has been called without any
127        subsequent calls to <STRONG>wrefresh</STRONG>, and <STRONG>FALSE</STRONG> otherwise.
128
129
130 </PRE><H3><a name="h3-set_term">set_term</a></H3><PRE>
131        The  <STRONG>set_term</STRONG>  routine  is  used to switch between different terminals.
132        The screen reference <STRONG>new</STRONG> becomes the new current terminal.  The  previ-
133        ous  terminal  is  returned  by  the routine.  This is the only routine
134        which manipulates <STRONG>SCREEN</STRONG> pointers; all other routines affect  only  the
135        current terminal.
136
137
138 </PRE><H3><a name="h3-delscreen">delscreen</a></H3><PRE>
139        The  <STRONG>delscreen</STRONG>  routine  frees  storage associated with the <STRONG>SCREEN</STRONG> data
140        structure.  The <STRONG>endwin</STRONG> routine does not do this, so <STRONG>delscreen</STRONG> should be
141        called after <STRONG>endwin</STRONG> if a particular <STRONG>SCREEN</STRONG> is no longer needed.
142
143
144 </PRE><H2><a name="h2-RETURN-VALUE">RETURN VALUE</a></H2><PRE>
145        <STRONG>endwin</STRONG> returns the integer <STRONG>ERR</STRONG> upon failure and <STRONG>OK</STRONG> upon successful com-
146        pletion.
147
148        Routines that return pointers always return <STRONG>NULL</STRONG> on error.
149
150        X/Open defines no error conditions.  In this implementation
151
152        <STRONG>o</STRONG>   <STRONG>endwin</STRONG> returns an error if the terminal was not initialized.
153
154        <STRONG>o</STRONG>   <STRONG>newterm</STRONG> returns an error if it cannot allocate the data  structures
155            for  the  screen,  or  for the top-level windows within the screen,
156            i.e., <STRONG>curscr</STRONG>, <STRONG>newscr</STRONG>, or <STRONG>stdscr</STRONG>.
157
158        <STRONG>o</STRONG>   <STRONG>set_term</STRONG> returns no error.
159
160
161 </PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
162        These functions were described in the XSI Curses standard, Issue 4.  As
163        of 2015, the current document is X/Open Curses, Issue 7.
164
165
166 </PRE><H3><a name="h3-Differences">Differences</a></H3><PRE>
167        X/Open  specifies that portable applications must not call <STRONG>initscr</STRONG> more
168        than once:
169
170        <STRONG>o</STRONG>   The portable way to use <STRONG>initscr</STRONG> is once only,  using  <STRONG>refresh</STRONG>  (see
171            <STRONG><A HREF="curs_refresh.3x.html">curs_refresh(3x)</A></STRONG>) to restore the screen after <STRONG>endwin</STRONG>.
172
173        <STRONG>o</STRONG>   This implementation allows using <STRONG>initscr</STRONG> after <STRONG>endwin</STRONG>.
174
175        Old versions of curses, e.g., BSD 4.4, may have returned a null pointer
176        from <STRONG>initscr</STRONG> when an error is detected, rather  than  exiting.   It  is
177        safe but redundant to check the return value of <STRONG>initscr</STRONG> in XSI Curses.
178
179
180 </PRE><H3><a name="h3-Unset-TERM-Variable">Unset TERM Variable</a></H3><PRE>
181        If  the  TERM variable is missing or empty, <STRONG>initscr</STRONG> uses the value "un-
182        known", which normally corresponds to a terminal entry with the <EM>generic</EM>
183        (<EM>gn</EM>)  capability.   Generic  entries  are  detected  by  <STRONG>setupterm</STRONG> (see
184        <STRONG><A HREF="curs_terminfo.3x.html">curs_terminfo(3x)</A></STRONG>) and cannot be used for full-screen operation.  Other
185        implementations may handle a missing/empty TERM variable differently.
186
187
188 </PRE><H3><a name="h3-Signal-Handlers">Signal Handlers</a></H3><PRE>
189        Quoting from X/Open Curses, section 3.1.1:
190
191             <EM>Curses</EM>  <EM>implementations</EM>  <EM>may</EM>  <EM>provide</EM>  <EM>for</EM> <EM>special</EM> <EM>handling</EM> <EM>of</EM> <EM>the</EM>
192             <STRONG>SIGINT</STRONG><EM>,</EM> <STRONG>SIGQUIT</STRONG>  <EM>and</EM>  <STRONG>SIGTSTP</STRONG>  <EM>signals</EM>  <EM>if</EM>  <EM>their</EM>  <EM>disposition</EM>  <EM>is</EM>
193             <STRONG>SIG_DFL</STRONG> <EM>at</EM> <EM>the</EM> <EM>time</EM> <STRONG>initscr</STRONG> <EM>is</EM> <EM>called</EM> <STRONG>...</STRONG>
194
195             <EM>Any</EM>  <EM>special</EM>  <EM>handling</EM>  <EM>for</EM> <EM>these</EM> <EM>signals</EM> <EM>may</EM> <EM>remain</EM> <EM>in</EM> <EM>effect</EM> <EM>for</EM>
196             <EM>the</EM> <EM>life</EM> <EM>of</EM> <EM>the</EM> <EM>process</EM> <EM>or</EM> <EM>until</EM> <EM>the</EM> <EM>process</EM> <EM>changes</EM> <EM>the</EM>  <EM>disposi-</EM>
197             <EM>tion</EM> <EM>of</EM> <EM>the</EM> <EM>signal.</EM>
198
199             <EM>None</EM>  <EM>of</EM> <EM>the</EM> <EM>Curses</EM> <EM>functions</EM> <EM>are</EM> <EM>required</EM> <EM>to</EM> <EM>be</EM> <EM>safe</EM> <EM>with</EM> <EM>respect</EM>
200             <EM>to</EM> <EM>signals</EM> ...
201
202        This implementation establishes signal handlers during  initialization,
203        e.g., <STRONG>initscr</STRONG> or <STRONG>newterm</STRONG>.  Applications which must handle these signals
204        should set up the corresponding handlers  <EM>after</EM>  initializing  the  li-
205        brary:
206
207        <STRONG>SIGINT</STRONG>
208             The  handler  <EM>attempts</EM> to cleanup the screen on exit.  Although it
209             <EM>usually</EM> works as expected, there are limitations:
210
211             <STRONG>o</STRONG>   Walking the <STRONG>SCREEN</STRONG> list is unsafe, since all  list  management
212                 is done without any signal blocking.
213
214             <STRONG>o</STRONG>   On systems which have <STRONG>REENTRANT</STRONG> turned on, <STRONG>set_term</STRONG> uses func-
215                 tions which could deadlock or misbehave in other ways.
216
217             <STRONG>o</STRONG>   <STRONG>endwin</STRONG> calls other functions, many of which use stdio or other
218                 library functions which are clearly unsafe.
219
220        <STRONG>SIGTERM</STRONG>
221             This  uses  the same handler as <STRONG>SIGINT</STRONG>, with the same limitations.
222             It is not mentioned in X/Open Curses, but  is  more  suitable  for
223             this purpose than <STRONG>SIGQUIT</STRONG> (which is used in debugging).
224
225        <STRONG>SIGTSTP</STRONG>
226             This  handles the <EM>stop</EM> signal, used in job control.  When resuming
227             the process,  this  implementation  discards  pending  input  with
228             <STRONG>flushinput</STRONG>  (see  <STRONG><A HREF="curs_util.3x.html">curs_util(3x)</A></STRONG>), and repaints the screen assuming
229             that it has been completely altered.  It also  updates  the  saved
230             terminal modes with <STRONG>def_shell_mode</STRONG> (see <STRONG><A HREF="curs_kernel.3x.html">curs_kernel(3x)</A></STRONG>).
231
232        <STRONG>SIGWINCH</STRONG>
233             This  handles  the  window-size  changes which were ignored in the
234             standardization efforts.  The handler sets a  (signal-safe)  vari-
235             able  which  is  later  tested in <STRONG>wgetch</STRONG> (see <STRONG><A HREF="curs_getch.3x.html">curs_getch(3x)</A></STRONG>).  If
236             <STRONG>keypad</STRONG> has been enabled for the corresponding window,  <STRONG>wgetch</STRONG>  re-
237             turns  the  key symbol <STRONG>KEY_RESIZE</STRONG>.  At the same time, <STRONG>wgetch</STRONG> calls
238             <STRONG>resizeterm</STRONG> to adjust the standard screen <STRONG>stdscr</STRONG>, and update  other
239             data such as <STRONG>LINES</STRONG> and <STRONG>COLS</STRONG>.
240
241
242 </PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
243        <STRONG><A HREF="ncurses.3x.html">curses(3x)</A></STRONG>,  <STRONG><A HREF="curs_kernel.3x.html">curs_kernel(3x)</A></STRONG>, <STRONG><A HREF="curs_refresh.3x.html">curs_refresh(3x)</A></STRONG>, <STRONG><A HREF="curs_slk.3x.html">curs_slk(3x)</A></STRONG>, <STRONG>curs_ter-</STRONG>
244        <STRONG><A HREF="curs_terminfo.3x.html">minfo(3x)</A></STRONG>, <STRONG><A HREF="curs_util.3x.html">curs_util(3x)</A></STRONG>, <STRONG><A HREF="curs_variables.3x.html">curs_variables(3x)</A></STRONG>.
245
246
247
248                                                               <STRONG><A HREF="curs_initscr.3x.html">curs_initscr(3x)</A></STRONG>
249 </PRE>
250 <div class="nav">
251 <ul>
252 <li><a href="#h2-NAME">NAME</a></li>
253 <li><a href="#h2-SYNOPSIS">SYNOPSIS</a></li>
254 <li><a href="#h2-DESCRIPTION">DESCRIPTION</a>
255 <ul>
256 <li><a href="#h3-initscr">initscr</a></li>
257 <li><a href="#h3-newterm">newterm</a></li>
258 <li><a href="#h3-endwin">endwin</a></li>
259 <li><a href="#h3-isendwin">isendwin</a></li>
260 <li><a href="#h3-set_term">set_term</a></li>
261 <li><a href="#h3-delscreen">delscreen</a></li>
262 </ul>
263 </li>
264 <li><a href="#h2-RETURN-VALUE">RETURN VALUE</a></li>
265 <li><a href="#h2-PORTABILITY">PORTABILITY</a>
266 <ul>
267 <li><a href="#h3-Differences">Differences</a></li>
268 <li><a href="#h3-Unset-TERM-Variable">Unset TERM Variable</a></li>
269 <li><a href="#h3-Signal-Handlers">Signal Handlers</a></li>
270 </ul>
271 </li>
272 <li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>
273 </ul>
274 </div>
275 </BODY>
276 </HTML>