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# main.cpp Example File

demos/glhypnotizer/main.cpp

     /****************************************************************************
     **
     ** Copyright (C) 2015 The Qt Company Ltd.
     ** Contact: http://www.qt.io/licensing/
     **
     ** This file is part of the demonstration applications of the Qt Toolkit.
     **
     ** $QT_BEGIN_LICENSE:LGPL$
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     ** Licensees holding valid commercial Qt licenses may use this file in
     ** accordance with the commercial license agreement provided with the
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     ** information use the contact form at http://www.qt.io/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
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     ** rights. These rights are described in The Qt Company LGPL Exception
     ** version 1.1, 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
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     ** $QT_END_LICENSE$
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     #include <QtGui>
     #include <QtOpenGL>
     #include <QtSvg>

     #define NUM_SWIRLY_ITEMS 10

     class GLPainter : public QObject
     {
         Q_OBJECT
     public:
         GLPainter(QGLWidget *widget);
         void stop();
         void resizeViewport(const QSize &size);

     public slots:
         void start();

     protected:
         void timerEvent(QTimerEvent *event);
         void paint();
         void initSwirlyItems();
         void updateSwirlyItems();
         void drawSuggestiveMessages(QPainter *p);

     private:
         QMutex mutex;
         QGLWidget *glWidget;
         int viewportWidth;
         int viewportHeight;
         bool doRendering;
         qreal rotationAngle;
         bool swirlClockwise;
         QSvgRenderer svgRenderer;
         QPixmap logo;
         QPainter::PixmapFragment swirlyItems[NUM_SWIRLY_ITEMS];
         int swirlyCounter;
         int textCounter;
         int messageYPos;
         qreal scaleFactor;
     };

     GLPainter::GLPainter(QGLWidget *widget)
         : glWidget(widget)
         , doRendering(true)
         , rotationAngle(rand() % 360)
         , swirlClockwise((rand() % 2) == 1)
         , svgRenderer(QLatin1String(":/spiral.svg"), this)
         , logo(QLatin1String(":/qt-logo.png"))
     {
     }

     void GLPainter::start()
     {
         glWidget->makeCurrent();
         startTimer(20);
     }

     void GLPainter::stop()
     {
         QMutexLocker locker(&mutex);
         doRendering = false;
     }

     void GLPainter::resizeViewport(const QSize &size)
     {
         QMutexLocker locker(&mutex);
         viewportWidth = size.width();
         viewportHeight = size.height();
         initSwirlyItems();
         textCounter = 0;
         messageYPos = -1;
     }

     void GLPainter::timerEvent(QTimerEvent *event)
     {
         QMutexLocker locker(&mutex);
         if (!doRendering) {
             killTimer(event->timerId());
             QThread::currentThread()->quit();
             return;
         }
         updateSwirlyItems();
         paint();
     }

     void GLPainter::paint()
     {
         QPainter p(glWidget);
         p.fillRect(QRect(0, 0, viewportWidth, viewportHeight), Qt::white);
         p.setRenderHints(QPainter::Antialiasing | QPainter::SmoothPixmapTransform);
         p.translate(viewportWidth / 2, viewportHeight / 2);
         p.rotate(rotationAngle * (swirlClockwise ? 1 : -1));
         p.scale(svgRenderer.viewBox().width() / 200.0 * 0.65,
                 svgRenderer.viewBox().height() / 200.0 * 0.65);
         p.translate(-viewportWidth / 2, -viewportHeight / 2);
         svgRenderer.render(&p);
         p.resetTransform();
         p.drawPixmapFragments(swirlyItems, NUM_SWIRLY_ITEMS, logo);
         drawSuggestiveMessages(&p);
         p.end();
         rotationAngle += 1.2;
     }

     void GLPainter::drawSuggestiveMessages(QPainter *p)
     {
         const int numSuggestiveMessages = 7;
         const char *texts[numSuggestiveMessages] = {" You feel relaxed.. ",
                                                     " Let your mind wander.. ",
                                                     " Look deep into the swirls.. ",
                                                     " Even deeper.. ",
                                                     " Qt is good! ",
                                                     " Qt is good for you! ",
                                                     " You MUST use Qt! "};
         QFont font(p->font());
         font.setPointSizeF(font.pointSizeF() * viewportWidth/200.0);
         p->setFont(font);
         QFontMetrics fm(font);
         int messageNo = textCounter/314;
         if (messageNo > 6 || messageNo < 0) {
             qFatal("This should not happen: %d - %d", messageNo, textCounter);
         }
         QLatin1String text(texts[textCounter / 314]);
         qreal textWidth = fm.width(text);
         int alpha = 255 * qAbs(qSin(textCounter * 0.01));
         if (messageYPos < 0 || (textCounter % 314 == 0)) {
             messageYPos = qBound(fm.height(), rand() % viewportHeight,
                                  viewportHeight - fm.height());
         }
         p->setPen(QColor(255, 255, 255, alpha));
         p->setBackground(QColor(50, 50, 50, qBound(0, alpha, 50)));
         p->setBackgroundMode(Qt::OpaqueMode);
         p->drawText((viewportWidth / 2) - (textWidth/ 2), messageYPos, text);
         ++textCounter;
         if (textCounter >= (314 * numSuggestiveMessages))
             textCounter = 0;
     }

     void GLPainter::initSwirlyItems()
     {
         swirlyCounter = swirlClockwise ? 0 : 360;
         scaleFactor = viewportWidth / 200.0;
         QRectF logoRect(0, 0, logo.width(), logo.height());

         for (int i=0; i<NUM_SWIRLY_ITEMS; ++i) {
             if (swirlClockwise) {
                 swirlyItems[i] = QPainter::PixmapFragment::create(QPointF(0, 0), logoRect,
                                                                   scaleFactor,
                                                                   scaleFactor);
             } else {
                 swirlyItems[i] = QPainter::PixmapFragment::create(QPointF(0, 0), logoRect,
                                                                   scaleFactor * 1 / 360.0,
                                                                   scaleFactor * 1 / 360.0);
             }
         }
     }

     void GLPainter::updateSwirlyItems()
     {
         swirlyCounter += swirlClockwise ? 1 : -1;

         for (int i=0; i<NUM_SWIRLY_ITEMS; ++i) {
             int factor;
             factor = swirlClockwise ? (swirlyCounter - i * 20) : (swirlyCounter + i * 20);
             if (factor > 0 && factor <= 360) {
                 swirlyItems[i].x = viewportWidth / 2.0 + qSin(factor * 0.05) * (viewportWidth / 2.0) * (100.0 / factor);
                 swirlyItems[i].y = viewportHeight / 2.0 + qCos(factor * 0.05) * (viewportHeight / 2.0) * (100.0 / factor);
                 swirlyItems[i].rotation += -swirlyCounter * 0.01;
                 swirlyItems[i].scaleX += swirlClockwise ? -scaleFactor * 1 / 360.0 : scaleFactor * 1 / 360.0;
                 if (swirlClockwise) {
                     if (swirlyItems[i].scaleX < 0)
                         swirlyItems[i].scaleX = scaleFactor;
                 } else {
                     if (swirlyItems[i].scaleX > scaleFactor)
                         swirlyItems[i].scaleX = scaleFactor * 1 / 360.0;
                 }
                 swirlyItems[i].scaleY = swirlyItems[i].scaleX;
             } else {
                 swirlyItems[i].scaleX = swirlyItems[i].scaleY = 0;
             }
         }
         if (swirlClockwise) {
             if (swirlyCounter > (360 + NUM_SWIRLY_ITEMS * 20))
                 swirlyCounter = 0;
         } else {
             if (swirlyCounter < -NUM_SWIRLY_ITEMS * 20)
                 swirlyCounter = 360;
         }
     }

     class GLWidget : public QGLWidget
     {
     public:
         GLWidget(QWidget *parent, QGLWidget *shareWidget = 0);
         ~GLWidget();
         void startRendering();
         void stopRendering();

     protected:
         void resizeEvent(QResizeEvent *event);
         void paintEvent(QPaintEvent *event);
         QSize sizeHint() const { return QSize(200, 200); }

     private:
         GLPainter glPainter;
         QThread glThread;
     };

     GLWidget::GLWidget(QWidget *parent, QGLWidget *share)
         : QGLWidget(QGLFormat(QGL::SampleBuffers), parent, share)
         , glPainter(this)
         , glThread(this)
     {
         setAttribute(Qt::WA_PaintOutsidePaintEvent);
         setAttribute(Qt::WA_DeleteOnClose);
     }

     GLWidget::~GLWidget()
     {
         stopRendering();
     }

     void GLWidget::startRendering()
     {
         glPainter.moveToThread(&glThread);
         connect(&glThread, SIGNAL(started()), &glPainter, SLOT(start()));
         glThread.start();
     }

     void GLWidget::stopRendering()
     {
         glPainter.stop();
         glThread.wait();
     }

     void GLWidget::resizeEvent(QResizeEvent *event)
     {
         glPainter.resizeViewport(event->size());
     }

     void GLWidget::paintEvent(QPaintEvent *)
     {
         // Handled by GLPainter.
     }

     class MainWindow : public QMainWindow
     {
         Q_OBJECT
     public:
         MainWindow();

     private slots:
         void newThread();
         void killThread();

     private:
         QMdiArea mdiArea;
         QGLWidget shareWidget;
     };

     MainWindow::MainWindow()
         : QMainWindow(0)
         , mdiArea(this)
         , shareWidget(this)
     {
         setWindowTitle("Qt GL Hypnotizer");
         QMenu *menu = menuBar()->addMenu("&Hypnotizers");
         menu->addAction("&New hypnotizer thread", this, SLOT(newThread()), QKeySequence("Ctrl+N"));
         menu->addAction("&End current hypnotizer thread", this, SLOT(killThread()), QKeySequence("Ctrl+K"));
         menu->addSeparator();
         menu->addAction("E&xit", qApp, SLOT(quit()), QKeySequence("Ctrl+Q"));

         setCentralWidget(&mdiArea);
         shareWidget.resize(1, 1);
         newThread();
     }

     void MainWindow::newThread()
     {
         static int windowCount = 1;
         if (mdiArea.subWindowList().count() > 9)
             return;
         GLWidget *widget = new GLWidget(&mdiArea, &shareWidget);
         mdiArea.addSubWindow(widget);
         widget->setWindowTitle("Thread #" + QString::number(windowCount++));
         widget->show();
         widget->startRendering();
     }

     void MainWindow::killThread()
     {
         delete mdiArea.activeSubWindow();
     }

     int main(int argc, char *argv[])
     {
         // Make Xlib and GLX thread safe under X11
         QApplication::setAttribute(Qt::AA_X11InitThreads);
         QApplication application(argc, argv);

         // Using QPainter to draw into QGLWidgets is only supported with GL 2.0
         if (!((QGLFormat::openGLVersionFlags() & QGLFormat::OpenGL_Version_2_0) ||
               (QGLFormat::openGLVersionFlags() & QGLFormat::OpenGL_ES_Version_2_0))) {
             QMessageBox::information(0, "Qt GL Hypnotizer",
                                      "This system does not support OpenGL 2.0 or OpenGL ES 2.0, "
                                      "which is required for this example to work.");
             return 0;
         }

         MainWindow mainWindow;
         mainWindow.show();
         return application.exec();
     }

     #include "main.moc"