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376 lines
11 KiB
C++
376 lines
11 KiB
C++
/****************************************************************************
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**
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** Copyright (C) 2015 The Qt Company Ltd.
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** Contact: http://www.qt.io/licensing/
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**
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** This file is part of the QtCore module of the Qt Toolkit.
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**
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** $QT_BEGIN_LICENSE:LGPL$
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** Commercial License Usage
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** Licensees holding valid commercial Qt licenses may use this file in
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** accordance with the commercial license agreement provided with the
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** Software or, alternatively, in accordance with the terms contained in
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** a written agreement between you and The Qt Company. For licensing terms
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** and conditions see http://www.qt.io/terms-conditions. For further
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** information use the contact form at http://www.qt.io/contact-us.
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**
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** GNU Lesser General Public License Usage
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** Alternatively, this file may be used under the terms of the GNU Lesser
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** General Public License version 2.1 or version 3 as published by the Free
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** Software Foundation and appearing in the file LICENSE.LGPLv21 and
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** LICENSE.LGPLv3 included in the packaging of this file. Please review the
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** following information to ensure the GNU Lesser General Public License
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** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
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** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
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**
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** As a special exception, The Qt Company gives you certain additional
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** rights. These rights are described in The Qt Company LGPL Exception
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** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
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**
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** GNU General Public License Usage
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** Alternatively, this file may be used under the terms of the GNU
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** General Public License version 3.0 as published by the Free Software
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** Foundation and appearing in the file LICENSE.GPL included in the
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** packaging of this file. Please review the following information to
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** ensure the GNU General Public License version 3.0 requirements will be
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** met: http://www.gnu.org/copyleft/gpl.html.
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**
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** $QT_END_LICENSE$
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**
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****************************************************************************/
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#include "qtimer.h"
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#include "qabstracteventdispatcher.h"
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#include "qcoreapplication.h"
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#include "qobject_p.h"
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QT_BEGIN_NAMESPACE
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/*!
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\class QTimer
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\brief The QTimer class provides repetitive and single-shot timers.
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\ingroup events
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The QTimer class provides a high-level programming interface for
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timers. To use it, create a QTimer, connect its timeout() signal
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to the appropriate slots, and call start(). From then on it will
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emit the timeout() signal at constant intervals.
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Example for a one second (1000 millisecond) timer (from the
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\l{widgets/analogclock}{Analog Clock} example):
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\snippet examples/widgets/analogclock/analogclock.cpp 4
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\snippet examples/widgets/analogclock/analogclock.cpp 5
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\snippet examples/widgets/analogclock/analogclock.cpp 6
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From then on, the \c update() slot is called every second.
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You can set a timer to time out only once by calling
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setSingleShot(true). You can also use the static
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QTimer::singleShot() function to call a slot after a specified
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interval:
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\snippet doc/src/snippets/timers/timers.cpp 3
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In multithreaded applications, you can use QTimer in any thread
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that has an event loop. To start an event loop from a non-GUI
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thread, use QThread::exec(). Qt uses the timer's
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\l{QObject::thread()}{thread affinity} to determine which thread
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will emit the \l{QTimer::}{timeout()} signal. Because of this, you
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must start and stop the timer in its thread; it is not possible to
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start a timer from another thread.
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As a special case, a QTimer with a timeout of 0 will time out as
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soon as all the events in the window system's event queue have
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been processed. This can be used to do heavy work while providing
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a snappy user interface:
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\snippet doc/src/snippets/timers/timers.cpp 4
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\snippet doc/src/snippets/timers/timers.cpp 5
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\snippet doc/src/snippets/timers/timers.cpp 6
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\c processOneThing() will from then on be called repeatedly. It
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should be written in such a way that it always returns quickly
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(typically after processing one data item) so that Qt can deliver
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events to widgets and stop the timer as soon as it has done all
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its work. This is the traditional way of implementing heavy work
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in GUI applications; multithreading is now becoming available on
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more and more platforms, and we expect that zero-millisecond
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QTimers will gradually be replaced by \l{QThread}s.
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\section1 Accuracy and Timer Resolution
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Timers will never time out earlier than the specified timeout value
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and they are not guaranteed to time out at the exact value specified.
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In many situations, they may time out late by a period of time that
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depends on the accuracy of the system timers.
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The accuracy of timers depends on the underlying operating system
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and hardware. Most platforms support a resolution of 1 millisecond,
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though the accuracy of the timer will not equal this resolution
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in many real-world situations.
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If Qt is unable to deliver the requested number of timer clicks,
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it will silently discard some.
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\section1 Alternatives to QTimer
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An alternative to using QTimer is to call QObject::startTimer()
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for your object and reimplement the QObject::timerEvent() event
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handler in your class (which must inherit QObject). The
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disadvantage is that timerEvent() does not support such
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high-level features as single-shot timers or signals.
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Another alternative to using QTimer is to use QBasicTimer. It is
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typically less cumbersome than using QObject::startTimer()
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directly. See \l{Timers} for an overview of all three approaches.
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Some operating systems limit the number of timers that may be
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used; Qt tries to work around these limitations.
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\sa QBasicTimer, QTimerEvent, QObject::timerEvent(), Timers,
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{Analog Clock Example}, {Wiggly Example}
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*/
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static const int INV_TIMER = -1; // invalid timer id
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/*!
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Constructs a timer with the given \a parent.
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*/
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QTimer::QTimer(QObject *parent)
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: QObject(parent), id(INV_TIMER), inter(0), del(0), single(0), nulltimer(0)
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{
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}
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/*!
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Destroys the timer.
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*/
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QTimer::~QTimer()
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{
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if (id != INV_TIMER) // stop running timer
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stop();
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}
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/*!
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\fn void QTimer::timeout()
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This signal is emitted when the timer times out.
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\sa interval, start(), stop()
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*/
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/*!
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\property QTimer::active
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\since 4.3
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This boolean property is true if the timer is running; otherwise
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false.
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*/
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/*!
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\fn bool QTimer::isActive() const
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Returns true if the timer is running (pending); otherwise returns
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false.
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*/
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/*!
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\fn int QTimer::timerId() const
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Returns the ID of the timer if the timer is running; otherwise returns
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-1.
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*/
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/*! \overload start()
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Starts or restarts the timer with the timeout specified in \l interval.
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If the timer is already running, it will be
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\l{QTimer::stop()}{stopped} and restarted.
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If \l singleShot is true, the timer will be activated only once.
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*/
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void QTimer::start()
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{
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if (id != INV_TIMER) // stop running timer
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stop();
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nulltimer = (!inter && single);
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id = QObject::startTimer(inter);
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}
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/*!
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Starts or restarts the timer with a timeout interval of \a msec
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milliseconds.
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If the timer is already running, it will be
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\l{QTimer::stop()}{stopped} and restarted.
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If \l singleShot is true, the timer will be activated only once.
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*/
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void QTimer::start(int msec)
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{
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inter = msec;
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start();
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}
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/*!
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Stops the timer.
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\sa start()
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*/
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void QTimer::stop()
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{
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if (id != INV_TIMER) {
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QObject::killTimer(id);
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id = INV_TIMER;
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}
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}
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/*!
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\reimp
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*/
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void QTimer::timerEvent(QTimerEvent *e)
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{
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if (e->timerId() == id) {
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if (single)
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stop();
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emit timeout();
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}
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}
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class QSingleShotTimer : public QObject
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{
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Q_OBJECT
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int timerId;
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public:
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~QSingleShotTimer();
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QSingleShotTimer(int msec, QObject *r, const char * m);
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Q_SIGNALS:
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void timeout();
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protected:
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void timerEvent(QTimerEvent *);
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};
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QSingleShotTimer::QSingleShotTimer(int msec, QObject *receiver, const char *member)
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: QObject(QAbstractEventDispatcher::instance())
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{
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connect(this, SIGNAL(timeout()), receiver, member);
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timerId = startTimer(msec);
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}
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QSingleShotTimer::~QSingleShotTimer()
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{
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if (timerId > 0)
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killTimer(timerId);
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}
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void QSingleShotTimer::timerEvent(QTimerEvent *)
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{
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// need to kill the timer _before_ we emit timeout() in case the
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// slot connected to timeout calls processEvents()
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if (timerId > 0)
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killTimer(timerId);
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timerId = -1;
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emit timeout();
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// we would like to use delete later here, but it feels like a
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// waste to post a new event to handle this event, so we just unset the flag
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// and explicitly delete...
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delete this;
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}
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QT_BEGIN_INCLUDE_NAMESPACE
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#include "moc_qtimer.cpp"
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#include "moc_qtimer.h"
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QT_END_INCLUDE_NAMESPACE
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/*!
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\reentrant
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This static function calls a slot after a given time interval.
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It is very convenient to use this function because you do not need
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to bother with a \link QObject::timerEvent() timerEvent\endlink or
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create a local QTimer object.
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Example:
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\snippet doc/src/snippets/code/src_corelib_kernel_qtimer.cpp 0
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This sample program automatically terminates after 10 minutes
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(600,000 milliseconds).
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The \a receiver is the receiving object and the \a member is the
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slot. The time interval is \a msec milliseconds.
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\sa start()
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*/
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void QTimer::singleShot(int msec, QObject *receiver, const char *member)
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{
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if (receiver && member) {
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if (msec == 0) {
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// special code shortpath for 0-timers
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const char* bracketPosition = strchr(member, '(');
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if (!bracketPosition || !(member[0] >= '0' && member[0] <= '3')) {
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qWarning("QTimer::singleShot: Invalid slot specification");
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return;
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}
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QByteArray methodName(member+1, bracketPosition - 1 - member); // extract method name
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QMetaObject::invokeMethod(receiver, methodName.constData(), Qt::QueuedConnection);
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return;
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}
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(void) new QSingleShotTimer(msec, receiver, member);
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}
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}
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/*!
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\property QTimer::singleShot
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\brief whether the timer is a single-shot timer
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A single-shot timer fires only once, non-single-shot timers fire
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every \l interval milliseconds.
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\sa interval, singleShot()
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*/
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/*!
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\property QTimer::interval
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\brief the timeout interval in milliseconds
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The default value for this property is 0. A QTimer with a timeout
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interval of 0 will time out as soon as all the events in the window
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system's event queue have been processed.
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Setting the interval of an active timer changes its timerId().
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\sa singleShot
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*/
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void QTimer::setInterval(int msec)
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{
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inter = msec;
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if (id != INV_TIMER) { // create new timer
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QObject::killTimer(id); // restart timer
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id = QObject::startTimer(msec);
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}
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}
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/*! \fn void QTimer::changeInterval(int msec)
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Use setInterval(msec) or start(msec) instead.
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*/
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QT_END_NAMESPACE
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