summaryrefslogtreecommitdiffstats
path: root/src/corelib/kernel/qtimer.cpp
blob: 8ca53b903427a3186ce024c4cc25d37ea00c4895 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** Contact: Qt Software Information (qt-info@nokia.com)
**
** This file is part of the QtCore module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** No Commercial Usage
** This file contains pre-release code and may not be distributed.
** You may use this file in accordance with the terms and conditions
** contained in the either Technology Preview License Agreement or the
** Beta Release License Agreement.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Nokia gives you certain
** additional rights. These rights are described in the Nokia Qt LGPL
** Exception version 1.0, included in the file LGPL_EXCEPTION.txt in this
** package.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3.0 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU General Public License version 3.0 requirements will be
** met: http://www.gnu.org/copyleft/gpl.html.
**
** If you are unsure which license is appropriate for your use, please
** contact the sales department at qt-sales@nokia.com.
** $QT_END_LICENSE$
**
****************************************************************************/

#include "qtimer.h"
#include "qabstracteventdispatcher.h"
#include "qcoreapplication.h"
#include "qobject_p.h"

QT_BEGIN_NAMESPACE

/*!
    \class QTimer
    \brief The QTimer class provides repetitive and single-shot timers.

    \ingroup time
    \ingroup events
    \mainclass

    The QTimer class provides a high-level programming interface for
    timers. To use it, create a QTimer, connect its timeout() signal
    to the appropriate slots, and call start(). From then on it will
    emit the timeout() signal at constant intervals.

    Example for a one second (1000 millisecond) timer (from the
    \l{widgets/analogclock}{Analog Clock} example):

    \snippet examples/widgets/analogclock/analogclock.cpp 4
    \snippet examples/widgets/analogclock/analogclock.cpp 5
    \snippet examples/widgets/analogclock/analogclock.cpp 6

    From then on, the \c update() slot is called every second.

    You can set a timer to time out only once by calling
    setSingleShot(true). You can also use the static
    QTimer::singleShot() function to call a slot after a specified
    interval:

    \snippet doc/src/snippets/timers/timers.cpp 3

    In multithreaded applications, you can use QTimer in any thread
    that has an event loop. To start an event loop from a non-GUI
    thread, use QThread::exec(). Qt uses the timer's
    \l{QObject::thread()}{thread affinity} to determine which thread
    will emit the \l{QTimer::}{timeout()} signal. Because of this, you
    must start and stop the timer in its thread; it is not possible to
    start a timer from another thread.

    As a special case, a QTimer with a timeout of 0 will time out as
    soon as all the events in the window system's event queue have
    been processed. This can be used to do heavy work while providing
    a snappy user interface:

    \snippet doc/src/snippets/timers/timers.cpp 4
    \snippet doc/src/snippets/timers/timers.cpp 5
    \snippet doc/src/snippets/timers/timers.cpp 6

    \c processOneThing() will from then on be called repeatedly. It
    should be written in such a way that it always returns quickly
    (typically after processing one data item) so that Qt can deliver
    events to widgets and stop the timer as soon as it has done all
    its work. This is the traditional way of implementing heavy work
    in GUI applications; multithreading is now becoming available on
    more and more platforms, and we expect that zero-millisecond
    QTimers will gradually be replaced by \l{QThread}s.

    Note that QTimer's accuracy depends on the underlying operating
    system and hardware. Most platforms support an accuracy of
    1 millisecond, but Windows 98 supports only 55. If Qt is
    unable to deliver the requested number of timer clicks, it will
    silently discard some.

    An alternative to using QTimer is to call QObject::startTimer()
    for your object and reimplement the QObject::timerEvent() event
    handler in your class (which must inherit QObject). The
    disadvantage is that timerEvent() does not support such
    high-level features as single-shot timers or signals.

    Another alternative to using QTimer is to use QBasicTimer. It is
    typically less cumbersome than using QObject::startTimer()
    directly. See \l{Timers} for an overview of all three approaches.

    Some operating systems limit the number of timers that may be
    used; Qt tries to work around these limitations.

    \sa QBasicTimer, QTimerEvent, QObject::timerEvent(), Timers,
        {Analog Clock Example}, {Wiggly Example}
*/


static const int INV_TIMER = -1;                // invalid timer id

/*!
    Constructs a timer with the given \a parent.
*/

QTimer::QTimer(QObject *parent)
    : QObject(parent), id(INV_TIMER), inter(0), del(0), single(0), nulltimer(0)
{
}


#ifdef QT3_SUPPORT
/*!
    Constructs a timer called \a name, with a \a parent.
*/

QTimer::QTimer(QObject *parent, const char *name)
    : QObject(parent), id(INV_TIMER), single(0), nulltimer(0)
{
    setObjectName(QString::fromAscii(name));
}
#endif

/*!
    Destroys the timer.
*/

QTimer::~QTimer()
{
    if (id != INV_TIMER)                        // stop running timer
        stop();
}


/*!
    \fn void QTimer::timeout()

    This signal is emitted when the timer times out.

    \sa interval, start(), stop()
*/

/*!
    \property QTimer::active
    \since 4.3

    This boolean property is true if the timer is running; otherwise
    false.
*/

/*!
    \fn bool QTimer::isActive() const

    Returns true if the timer is running (pending); otherwise returns
    false.
*/

/*!
    \fn int QTimer::timerId() const

    Returns the ID of the timer if the timer is running; otherwise returns
    -1.
*/


/*! \overload start()

    Starts or restarts the timer with the timeout specified in \l interval.

    If \l singleShot is true, the timer will be activated only once.
*/
void QTimer::start()
{
    if (id != INV_TIMER)                        // stop running timer
        stop();
    nulltimer = (!inter && single);
    id = QObject::startTimer(inter);
}

/*!
    Starts or restarts the timer with a timeout interval of \a msec
    milliseconds.
*/
void QTimer::start(int msec)
{
    inter = msec;
    start();
}


#ifdef QT3_SUPPORT
/*! \overload start()

  Call setSingleShot(\a sshot) and start(\a msec) instead.
*/

int QTimer::start(int msec, bool sshot)
{
    if (id >=0 && nulltimer && !msec && sshot)
        return id;
    stop();
    setInterval(msec);
    setSingleShot(sshot);
    start();
    return timerId();
}
#endif


/*!
    Stops the timer.

    \sa start()
*/

void QTimer::stop()
{
    if (id != INV_TIMER) {
        QObject::killTimer(id);
        id = INV_TIMER;
    }
}


/*!
    \reimp
*/
void QTimer::timerEvent(QTimerEvent *e)
{
    if (e->timerId() == id) {
        if (single)
            stop();
        emit timeout();
    }
}

class QSingleShotTimer : public QObject
{
    Q_OBJECT
    int timerId;
public:
    ~QSingleShotTimer();
    QSingleShotTimer(int msec, QObject *r, const char * m);
Q_SIGNALS:
    void timeout();
protected:
    void timerEvent(QTimerEvent *);
};

QSingleShotTimer::QSingleShotTimer(int msec, QObject *receiver, const char *member)
    : QObject(QAbstractEventDispatcher::instance())
{
    connect(this, SIGNAL(timeout()), receiver, member);
    timerId = startTimer(msec);
}

QSingleShotTimer::~QSingleShotTimer()
{
    if (timerId > 0)
        killTimer(timerId);
}

void QSingleShotTimer::timerEvent(QTimerEvent *)
{
    // need to kill the timer _before_ we emit timeout() in case the
    // slot connected to timeout calls processEvents()
    if (timerId > 0)
        killTimer(timerId);
    timerId = -1;
    emit timeout();

    // we would like to use delete later here, but it feels like a
    // waste to post a new event to handle this event, so we just unset the flag
    // and explicitly delete...
    qDeleteInEventHandler(this);
}

QT_BEGIN_INCLUDE_NAMESPACE
#include "qtimer.moc"
QT_END_INCLUDE_NAMESPACE

/*!
    \reentrant
    This static function calls a slot after a given time interval.

    It is very convenient to use this function because you do not need
    to bother with a \link QObject::timerEvent() timerEvent\endlink or
    create a local QTimer object.

    Example:
    \snippet doc/src/snippets/code/src_corelib_kernel_qtimer.cpp 0

    This sample program automatically terminates after 10 minutes
    (600,000 milliseconds).

    The \a receiver is the receiving object and the \a member is the
    slot. The time interval is \a msec milliseconds.

    \sa start()
*/

void QTimer::singleShot(int msec, QObject *receiver, const char *member)
{
    if (receiver && member)
        (void) new QSingleShotTimer(msec, receiver, member);
}

/*!
    \property QTimer::singleShot
    \brief whether the timer is a single-shot timer

    A single-shot timer fires only once, non-single-shot timers fire
    every \l interval milliseconds.

    \sa interval, singleShot()
*/

/*!
    \property QTimer::interval
    \brief the timeout interval in milliseconds

    The default value for this property is 0.  A QTimer with a timeout
    interval of 0 will time out as soon as all the events in the window
    system's event queue have been processed.

    Setting the interval of an active timer changes its timerId().

    \sa singleShot
*/
void QTimer::setInterval(int msec)
{
    inter = msec;
    if (id != INV_TIMER) {                        // create new timer
        QObject::killTimer(id);                        // restart timer
        id = QObject::startTimer(msec);
    }
}

/*! \fn void QTimer::changeInterval(int msec)

   Use setInterval(msec) or start(msec) instead.
*/

QT_END_NAMESPACE