summaryrefslogtreecommitdiff
path: root/src/corelib/kernel/qeventloop.cpp
blob: 1059ac9d6783231c147e6c9d70c508bd56fc05eb (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
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
/****************************************************************************
**
** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
** Contact: http://www.qt-project.org/legal
**
** This file is part of the QtCore module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL21$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and Digia. For licensing terms and
** conditions see http://qt.digia.com/licensing. For further information
** use the contact form at http://qt.digia.com/contact-us.
**
** 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 or version 3 as published by the Free
** Software Foundation and appearing in the file LICENSE.LGPLv21 and
** LICENSE.LGPLv3 included in the packaging of this file. Please review the
** following information to ensure the GNU Lesser General Public License
** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Digia gives you certain additional
** rights. These rights are described in the Digia Qt LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** $QT_END_LICENSE$
**
****************************************************************************/

#include "qeventloop.h"

#include "qabstracteventdispatcher.h"
#include "qcoreapplication.h"
#include "qcoreapplication_p.h"
#include "qelapsedtimer.h"

#include "qobject_p.h"
#include "qeventloop_p.h"
#include <private/qthread_p.h>

QT_BEGIN_NAMESPACE

/*!
    \class QEventLoop
    \inmodule QtCore
    \brief The QEventLoop class provides a means of entering and leaving an event loop.

    At any time, you can create a QEventLoop object and call exec()
    on it to start a local event loop. From within the event loop,
    calling exit() will force exec() to return.

    \sa QAbstractEventDispatcher
*/

/*!
    \enum QEventLoop::ProcessEventsFlag

    This enum controls the types of events processed by the
    processEvents() functions.

    \value AllEvents All events. Note that
    \l{QEvent::DeferredDelete}{DeferredDelete} events are processed
    specially. See QObject::deleteLater() for more details.

    \value ExcludeUserInputEvents Do not process user input events,
    such as ButtonPress and KeyPress. Note that the events are not
    discarded; they will be delivered the next time processEvents() is
    called without the ExcludeUserInputEvents flag.

    \value ExcludeSocketNotifiers Do not process socket notifier
    events. Note that the events are not discarded; they will be
    delivered the next time processEvents() is called without the
    ExcludeSocketNotifiers flag.

    \value WaitForMoreEvents Wait for events if no pending events are
    available.

    \omitvalue X11ExcludeTimers
    \omitvalue EventLoopExec
    \omitvalue DialogExec

    \sa processEvents()
*/

/*!
    Constructs an event loop object with the given \a parent.
*/
QEventLoop::QEventLoop(QObject *parent)
    : QObject(*new QEventLoopPrivate, parent)
{
    Q_D(QEventLoop);
    if (!QCoreApplication::instance()) {
        qWarning("QEventLoop: Cannot be used without QApplication");
    } else if (!d->threadData->eventDispatcher.load()) {
        QThreadPrivate::createEventDispatcher(d->threadData);
    }
}

/*!
    Destroys the event loop object.
*/
QEventLoop::~QEventLoop()
{ }


/*!
    Processes pending events that match \a flags until there are no
    more events to process. Returns \c true if pending events were handled;
    otherwise returns \c false.

    This function is especially useful if you have a long running
    operation and want to show its progress without allowing user
    input; i.e. by using the \l ExcludeUserInputEvents flag.

    This function is simply a wrapper for
    QAbstractEventDispatcher::processEvents(). See the documentation
    for that function for details.
*/
bool QEventLoop::processEvents(ProcessEventsFlags flags)
{
    Q_D(QEventLoop);
    if (!d->threadData->eventDispatcher.load())
        return false;
    return d->threadData->eventDispatcher.load()->processEvents(flags);
}

/*!
    Enters the main event loop and waits until exit() is called.
    Returns the value that was passed to exit().

    If \a flags are specified, only events of the types allowed by
    the \a flags will be processed.

    It is necessary to call this function to start event handling. The
    main event loop receives events from the window system and
    dispatches these to the application widgets.

    Generally speaking, no user interaction can take place before
    calling exec(). As a special case, modal widgets like QMessageBox
    can be used before calling exec(), because modal widgets
    use their own local event loop.

    To make your application perform idle processing (i.e. executing a
    special function whenever there are no pending events), use a
    QTimer with 0 timeout. More sophisticated idle processing schemes
    can be achieved using processEvents().

    \sa QCoreApplication::quit(), exit(), processEvents()
*/
int QEventLoop::exec(ProcessEventsFlags flags)
{
    Q_D(QEventLoop);
    //we need to protect from race condition with QThread::exit
    QMutexLocker locker(&static_cast<QThreadPrivate *>(QObjectPrivate::get(d->threadData->thread))->mutex);
    if (d->threadData->quitNow)
        return -1;

    if (d->inExec) {
        qWarning("QEventLoop::exec: instance %p has already called exec()", this);
        return -1;
    }

    struct LoopReference {
        QEventLoopPrivate *d;
        QMutexLocker &locker;

        bool exceptionCaught;
        LoopReference(QEventLoopPrivate *d, QMutexLocker &locker) : d(d), locker(locker), exceptionCaught(true)
        {
            d->inExec = true;
            d->exit.storeRelease(false);
            ++d->threadData->loopLevel;
            d->threadData->eventLoops.push(d->q_func());
            locker.unlock();
        }

        ~LoopReference()
        {
            if (exceptionCaught) {
                qWarning("Qt has caught an exception thrown from an event handler. Throwing\n"
                         "exceptions from an event handler is not supported in Qt. You must\n"
                         "reimplement QApplication::notify() and catch all exceptions there.\n");
            }
            locker.relock();
            QEventLoop *eventLoop = d->threadData->eventLoops.pop();
            Q_ASSERT_X(eventLoop == d->q_func(), "QEventLoop::exec()", "internal error");
            Q_UNUSED(eventLoop); // --release warning
            d->inExec = false;
            --d->threadData->loopLevel;
        }
    };
    LoopReference ref(d, locker);

    // remove posted quit events when entering a new event loop
    QCoreApplication *app = QCoreApplication::instance();
    if (app && app->thread() == thread())
        QCoreApplication::removePostedEvents(app, QEvent::Quit);

    while (!d->exit.loadAcquire())
        processEvents(flags | WaitForMoreEvents | EventLoopExec);

    ref.exceptionCaught = false;
    return d->returnCode.load();
}

/*!
    Process pending events that match \a flags for a maximum of \a
    maxTime milliseconds, or until there are no more events to
    process, whichever is shorter.
    This function is especially useful if you have a long running
    operation and want to show its progress without allowing user
    input, i.e. by using the \l ExcludeUserInputEvents flag.

    \b{Notes:}
    \list
    \li This function does not process events continuously; it
       returns after all available events are processed.
    \li Specifying the \l WaitForMoreEvents flag makes no sense
       and will be ignored.
    \endlist
*/
void QEventLoop::processEvents(ProcessEventsFlags flags, int maxTime)
{
    Q_D(QEventLoop);
    if (!d->threadData->eventDispatcher.load())
        return;

    QElapsedTimer start;
    start.start();
    while (processEvents(flags & ~WaitForMoreEvents)) {
        if (start.elapsed() > maxTime)
            break;
    }
}

/*!
    Tells the event loop to exit with a return code.

    After this function has been called, the event loop returns from
    the call to exec(). The exec() function returns \a returnCode.

    By convention, a \a returnCode of 0 means success, and any non-zero
    value indicates an error.

    Note that unlike the C library function of the same name, this
    function \e does return to the caller -- it is event processing that
    stops.

    \sa QCoreApplication::quit(), quit(), exec()
*/
void QEventLoop::exit(int returnCode)
{
    Q_D(QEventLoop);
    if (!d->threadData->eventDispatcher.load())
        return;

    d->returnCode.store(returnCode);
    d->exit.storeRelease(true);
    d->threadData->eventDispatcher.load()->interrupt();
}

/*!
    Returns \c true if the event loop is running; otherwise returns
    false. The event loop is considered running from the time when
    exec() is called until exit() is called.

    \sa exec(), exit()
 */
bool QEventLoop::isRunning() const
{
    Q_D(const QEventLoop);
    return !d->exit.loadAcquire();
}

/*!
    Wakes up the event loop.

    \sa QAbstractEventDispatcher::wakeUp()
*/
void QEventLoop::wakeUp()
{
    Q_D(QEventLoop);
    if (!d->threadData->eventDispatcher.load())
        return;
    d->threadData->eventDispatcher.load()->wakeUp();
}


/*!
    \reimp
*/
bool QEventLoop::event(QEvent *event)
{
    if (event->type() == QEvent::Quit) {
        quit();
        return true;
    } else {
        return QObject::event(event);
    }
}

/*!
    Tells the event loop to exit normally.

    Same as exit(0).

    \sa QCoreApplication::quit(), exit()
*/
void QEventLoop::quit()
{ exit(0); }


class QEventLoopLockerPrivate
{
public:
    explicit QEventLoopLockerPrivate(QEventLoopPrivate *loop)
      : loop(loop), type(EventLoop)
    {
        loop->ref();
    }

    explicit QEventLoopLockerPrivate(QThreadPrivate *thread)
      : thread(thread), type(Thread)
    {
        thread->ref();
    }

    explicit QEventLoopLockerPrivate(QCoreApplicationPrivate *app)
      : app(app), type(Application)
    {
        app->ref();
    }

    ~QEventLoopLockerPrivate()
    {
        switch (type)
        {
        case EventLoop:
            loop->deref();
            break;
        case Thread:
            thread->deref();
            break;
        default:
            app->deref();
            break;
        }
    }

private:
    union {
        QEventLoopPrivate * loop;
        QThreadPrivate * thread;
        QCoreApplicationPrivate * app;
    };
    enum Type {
        EventLoop,
        Thread,
        Application
    };
    const Type type;
};

/*!
    \class QEventLoopLocker
    \inmodule QtCore
    \brief The QEventLoopLocker class provides a means to quit an event loop when it is no longer needed.
    \since 5.0

    The QEventLoopLocker operates on particular objects - either a QCoreApplication
    instance, a QEventLoop instance or a QThread instance.

    This makes it possible to, for example, run a batch of jobs with an event loop
    and exit that event loop after the last job is finished. That is accomplished
    by keeping a QEventLoopLocker with each job instance.

    The variant which operates on QCoreApplication makes it possible to finish
    asynchronously running jobs after the last gui window has been closed. This
    can be useful for example for running a job which uploads data to a network.

    \sa QEventLoop, QCoreApplication
*/

/*!
    Creates an event locker operating on the QCoreApplication.

    The application will quit when there are no more QEventLoopLockers operating on it.

    \sa QCoreApplication::quit(), QCoreApplication::isQuitLockEnabled()
 */
QEventLoopLocker::QEventLoopLocker()
  : d_ptr(new QEventLoopLockerPrivate(static_cast<QCoreApplicationPrivate*>(QObjectPrivate::get(QCoreApplication::instance()))))
{

}

/*!
    Creates an event locker operating on the \a loop.

    This particular QEventLoop will quit when there are no more QEventLoopLockers operating on it.

    \sa QEventLoop::quit()
 */
QEventLoopLocker::QEventLoopLocker(QEventLoop *loop)
  : d_ptr(new QEventLoopLockerPrivate(static_cast<QEventLoopPrivate*>(QObjectPrivate::get(loop))))
{

}

/*!
    Creates an event locker operating on the \a thread.

    This particular QThread will quit when there are no more QEventLoopLockers operating on it.

    \sa QThread::quit()
 */
QEventLoopLocker::QEventLoopLocker(QThread *thread)
  : d_ptr(new QEventLoopLockerPrivate(static_cast<QThreadPrivate*>(QObjectPrivate::get(thread))))
{

}

/*!
    Destroys this event loop locker object
 */
QEventLoopLocker::~QEventLoopLocker()
{
    delete d_ptr;
}

QT_END_NAMESPACE