main.cpp Example File

 /****************************************************************************
 **
 ** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies).
 ** Contact: http://www.qt-project.org/
 **
 ** This file is part of the demonstration applications of the Qt Toolkit.
 **
 ** $QT_BEGIN_LICENSE:LGPL$
 ** GNU Lesser General Public License Usage
 ** 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 1.1, 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 met:
 ** http://www.gnu.org/copyleft/gpl.html.
 **
 ** Other Usage
 ** Alternatively, this file may be used in accordance with the terms and
 ** conditions contained in a signed written agreement between you and Nokia.
 **
 **
 **
 **
 **
 **
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/

 //#include <GL/glew.h>
 #include "glextensions.h"

 #include "scene.h"

 #include <QtWidgets>
 #include <QGLWidget>

 class GraphicsView : public QGraphicsView
 {
 public:
     GraphicsView()
     {
         setWindowTitle(tr("Boxes"));
         setRenderHints(QPainter::Antialiasing | QPainter::SmoothPixmapTransform);
         //setRenderHints(QPainter::SmoothPixmapTransform);
     }

 protected:
     void resizeEvent(QResizeEvent *event) {
         if (scene())
             scene()->setSceneRect(QRect(QPoint(0, 0), event->size()));
         QGraphicsView::resizeEvent(event);
     }
 };

 inline bool matchString(const char *extensionString, const char *subString)
 {
     int subStringLength = strlen(subString);
     return (strncmp(extensionString, subString, subStringLength) == 0)
         && ((extensionString[subStringLength] == ' ') || (extensionString[subStringLength] == '\0'));
 }

 bool necessaryExtensionsSupported()
 {
     const char *extensionString = reinterpret_cast<const char *>(glGetString(GL_EXTENSIONS));
     const char *p = extensionString;

     const int GL_EXT_FBO = 1;
     const int GL_ARB_VS = 2;
     const int GL_ARB_FS = 4;
     const int GL_ARB_SO = 8;
     int extensions = 0;

     while (*p) {
         if (matchString(p, "GL_EXT_framebuffer_object"))
             extensions |= GL_EXT_FBO;
         else if (matchString(p, "GL_ARB_vertex_shader"))
             extensions |= GL_ARB_VS;
         else if (matchString(p, "GL_ARB_fragment_shader"))
             extensions |= GL_ARB_FS;
         else if (matchString(p, "GL_ARB_shader_objects"))
             extensions |= GL_ARB_SO;
         while ((*p != ' ') && (*p != '\0'))
             ++p;
         if (*p == ' ')
             ++p;
     }
     return (extensions == 15);
 }

 int main(int argc, char **argv)
 {
     QApplication app(argc, argv);

     if ((QGLFormat::openGLVersionFlags() & QGLFormat::OpenGL_Version_1_5) == 0) {
         QMessageBox::critical(0, "OpenGL features missing",
             "OpenGL version 1.5 or higher is required to run this demo.\n"
             "The program will now exit.");
         return -1;
     }

     int maxTextureSize = 1024;
     QGLWidget *widget = new QGLWidget(QGLFormat(QGL::SampleBuffers));
     widget->makeCurrent();

     if (!necessaryExtensionsSupported()) {
         QMessageBox::critical(0, "OpenGL features missing",
             "The OpenGL extensions required to run this demo are missing.\n"
             "The program will now exit.");
         delete widget;
         return -2;
     }

     // Check if all the necessary functions are resolved.
     if (!getGLExtensionFunctions().resolve(widget->context())) {
         QMessageBox::critical(0, "OpenGL features missing",
             "Failed to resolve OpenGL functions required to run this demo.\n"
             "The program will now exit.");
         delete widget;
         return -3;
     }

     // TODO: Make conditional for final release
     QMessageBox::information(0, "For your information",
         "This demo can be GPU and CPU intensive and may\n"
         "work poorly or not at all on your system.");

     widget->makeCurrent(); // The current context must be set before calling Scene's constructor
     Scene scene(1024, 768, maxTextureSize);
     GraphicsView view;
     view.setViewport(widget);
     view.setViewportUpdateMode(QGraphicsView::FullViewportUpdate);
     view.setScene(&scene);
     view.show();

     return app.exec();
 }