main.cpp Example File

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  //#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) override {
          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();
  }