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# main.cpp Example File
demos/boxes/main.cpp

     /****************************************************************************
     **
     ** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
     ** All rights reserved.
     ** Contact: Nokia Corporation (qt-info@nokia.com)
     **
     ** This file is part of the demonstration applications of the Qt Toolkit.
     **
     ** $QT_BEGIN_LICENSE:LGPL$
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     ** Licensees holding valid Qt Commercial licenses may use this file in
     ** accordance with the Qt Commercial License Agreement provided with the
     ** Software or, alternatively, in accordance with the terms contained in
     ** a written agreement between you and Nokia.
     **
     ** 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 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.
     **
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     ** 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.
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     //#include <GL/glew.h>
     #include "glextensions.h"

     #include "scene.h"

     #include <QtGui>
     #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();
     }