Qt 5.6 | Qt Widgets | Boxes | main.cpp Example File

Qt 5.6.2 Reference Documentation

# main.cpp Example File

graphicsview/boxes/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.
      **
      ** $QT_BEGIN_LICENSE:LGPL21$
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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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      **
      ** 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
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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) Q_DECL_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();
      }