glwidget.cpp Example File
^{opengl/samplebuffers/glwidget.cpp}

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    **
    ** Copyright (C) 2005-2006 Trolltech ASA. All rights reserved.
    **
    ** This file is part of the documentation of the Qt Toolkit.
    **
    ** This file may be used under the terms of the GNU General Public
    ** License version 2.0 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 GNU
    ** General Public Licensing requirements will be met:
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    ** review the following information:
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    #include "glwidget.h"
    #include <math.h>

    #ifndef GL_MULTISAMPLE
    #define GL_MULTISAMPLE  0x809D
    #endif

    GLWidget::GLWidget(QWidget *parent)
        : QGLWidget(QGLFormat(QGL::SampleBuffers), parent)
    {
        startTimer(40);
        setWindowTitle(tr("Sample Buffers"));
    }

    void GLWidget::initializeGL()
    {
        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        glOrtho(-.5, .5, .5, -.5, -1000, 1000);
        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();
        glClearColor(1.0f, 1.0f, 1.0f, 1.0f);

        makeObject();
    }

    void GLWidget::resizeGL(int w, int h)
    {
        glViewport(0, 0, w, h);
    }

    void GLWidget::paintGL()
    {
        static float rot = 0.0;
        glClear(GL_COLOR_BUFFER_BIT);

        glMatrixMode(GL_MODELVIEW);
        glPushMatrix();
        glEnable(GL_MULTISAMPLE);
        glTranslatef(-0.25f, -0.10f, 0.0f);
        glScalef(0.75f, 1.15f, 0.0f);
        glRotatef(rot, 0.0f, 0.f, 1.0f);
        glCallList(list);
        glPopMatrix();

        glPushMatrix();
        glDisable(GL_MULTISAMPLE);
        glTranslatef(0.25f, -0.10f, 0.0f);
        glScalef(0.75f, 1.15f, 0.0f);
        glRotatef(rot, 0.0f, 0.0f, 1.0f);
        glCallList(list);
        glPopMatrix();

        rot += 0.2f;

        qglColor(Qt::black);
        renderText(-0.35, 0.4, 0.0, "Multisampling enabled");
        renderText(0.15, 0.4, 0.0, "Multisampling disabled");
    }

    void GLWidget::timerEvent(QTimerEvent *)
    {
        update();
    }

    void GLWidget::makeObject()
    {
        QColor trolltechGreen(QColor::fromCmykF(0.40, 0.0, 1.0, 0.0));
        const double Pi = 3.14159265358979323846;
        const int NumSectors = 15;
        GLdouble x1 = +0.06;
        GLdouble y1 = -0.14;
        GLdouble x2 = +0.14;
        GLdouble y2 = -0.06;
        GLdouble x3 = +0.08;
        GLdouble y3 = +0.00;
        GLdouble x4 = +0.30;
        GLdouble y4 = +0.22;

        list = glGenLists(1);
        glNewList(list, GL_COMPILE);
        {
            for (int i = 0; i < NumSectors; ++i) {
                double angle1 = (i * 2 * Pi) / NumSectors;
                GLdouble x5 = 0.30 * sin(angle1);
                GLdouble y5 = 0.30 * cos(angle1);
                GLdouble x6 = 0.20 * sin(angle1);
                GLdouble y6 = 0.20 * cos(angle1);

                double angle2 = ((i + 1) * 2 * Pi) / NumSectors;
                GLdouble x7 = 0.20 * sin(angle2);
                GLdouble y7 = 0.20 * cos(angle2);
                GLdouble x8 = 0.30 * sin(angle2);
                GLdouble y8 = 0.30 * cos(angle2);

                qglColor(trolltechGreen);
                quad(GL_QUADS, x5, y5, x6, y6, x7, y7, x8, y8);
                qglColor(Qt::black);
                quad(GL_LINE_LOOP, x5, y5, x6, y6, x7, y7, x8, y8);
            }

            qglColor(trolltechGreen);
            quad(GL_QUADS, x1, y1, x2, y2, y2, x2, y1, x1);
            quad(GL_QUADS, x3, y3, x4, y4, y4, x4, y3, x3);

            qglColor(Qt::black);
            quad(GL_LINE_LOOP, x1, y1, x2, y2, y2, x2, y1, x1);
            quad(GL_LINE_LOOP, x3, y3, x4, y4, y4, x4, y3, x3);
        }
        glEndList();
    }

    void GLWidget::quad(GLenum primitive, GLdouble x1, GLdouble y1, GLdouble x2, GLdouble y2,
                        GLdouble x3, GLdouble y3, GLdouble x4, GLdouble y4)
    {
        glBegin(primitive);
        {
            glVertex2d(x1, y1);
            glVertex2d(x2, y2);
            glVertex2d(x3, y3);
            glVertex2d(x4, y4);
        }
        glEnd();
    }