- Qt 5.5
- Qt Widgets
- Boxes
- main.cpp Example File
- Qt 5.5.1 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.
    **
    ** $QT_BEGIN_LICENSE:LGPL21$
    ** Commercial License Usage
    ** Licensees holding valid commercial Qt licenses may use this file in
    ** accordance with the commercial license agreement provided with the
    ** Software or, alternatively, in accordance with the terms contained in
    ** a written agreement between you and The Qt Company. For licensing terms
    ** and conditions see http://www.qt.io/terms-conditions. For further
    ** 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
    ** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
    ** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
    **
    ** As a special exception, The Qt Company gives you certain additional
    ** rights. These rights are described in The Qt Company LGPL Exception
    ** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
    **
    ** $QT_END_LICENSE$
    **
    ****************************************************************************/

    //#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) 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();
    }