Qt Reference Documentation

# plugin.cpp Example File

declarative/cppextensions/plugins/plugin.cpp

     /****************************************************************************
     **
     ** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
     ** All rights reserved.
     ** Contact: Nokia Corporation (qt-info@nokia.com)
     **
     ** This file is part of the examples of the Qt Toolkit.
     **
     ** $QT_BEGIN_LICENSE:BSD$
     ** You may use this file under the terms of the BSD license as follows:
     **
     ** "Redistribution and use in source and binary forms, with or without
     ** modification, are permitted provided that the following conditions are
     ** met:
     **   * Redistributions of source code must retain the above copyright
     **     notice, this list of conditions and the following disclaimer.
     **   * Redistributions in binary form must reproduce the above copyright
     **     notice, this list of conditions and the following disclaimer in
     **     the documentation and/or other materials provided with the
     **     distribution.
     **   * Neither the name of Nokia Corporation and its Subsidiary(-ies) nor
     **     the names of its contributors may be used to endorse or promote
     **     products derived from this software without specific prior written
     **     permission.
     **
     ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     ** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
     ** $QT_END_LICENSE$
     **
     ****************************************************************************/

     #include <QtDeclarative/QDeclarativeExtensionPlugin>
     #include <QtDeclarative/qdeclarative.h>
     #include <qdebug.h>
     #include <qdatetime.h>
     #include <qbasictimer.h>
     #include <qapplication.h>

     // Implements a "TimeModel" class with hour and minute properties
     // that change on-the-minute yet efficiently sleep the rest
     // of the time.

     class MinuteTimer : public QObject
     {
         Q_OBJECT
     public:
         MinuteTimer(QObject *parent) : QObject(parent)
         {
         }

         void start()
         {
             if (!timer.isActive()) {
                 time = QTime::currentTime();
                 timer.start(60000-time.second()*1000, this);
             }
         }

         void stop()
         {
             timer.stop();
         }

         int hour() const { return time.hour(); }
         int minute() const { return time.minute(); }

     signals:
         void timeChanged();

     protected:
         void timerEvent(QTimerEvent *)
         {
             QTime now = QTime::currentTime();
             if (now.second() == 59 && now.minute() == time.minute() && now.hour() == time.hour()) {
                 // just missed time tick over, force it, wait extra 0.5 seconds
                 time.addSecs(60);
                 timer.start(60500, this);
             } else {
                 time = now;
                 timer.start(60000-time.second()*1000, this);
             }
             emit timeChanged();
         }

     private:
         QTime time;
         QBasicTimer timer;
     };

     class TimeModel : public QObject
     {
         Q_OBJECT
         Q_PROPERTY(int hour READ hour NOTIFY timeChanged)
         Q_PROPERTY(int minute READ minute NOTIFY timeChanged)

     public:
         TimeModel(QObject *parent=0) : QObject(parent)
         {
             if (++instances == 1) {
                 if (!timer)
                     timer = new MinuteTimer(qApp);
                 connect(timer, SIGNAL(timeChanged()), this, SIGNAL(timeChanged()));
                 timer->start();
             }
         }

         ~TimeModel()
         {
             if (--instances == 0) {
                 timer->stop();
             }
         }

         int minute() const { return timer->minute(); }
         int hour() const { return timer->hour(); }

     signals:
         void timeChanged();

     private:
         QTime t;
         static MinuteTimer *timer;
         static int instances;
     };

     int TimeModel::instances=0;
     MinuteTimer *TimeModel::timer=0;

     class QExampleQmlPlugin : public QDeclarativeExtensionPlugin
     {
         Q_OBJECT
     public:
         void registerTypes(const char *uri)
         {
             Q_ASSERT(uri == QLatin1String("com.nokia.TimeExample"));
             qmlRegisterType<TimeModel>(uri, 1, 0, "Time");
         }
     };

     #include "plugin.moc"

     Q_EXPORT_PLUGIN2(qmlqtimeexampleplugin, QExampleQmlPlugin);