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# glwidget.cpp Example File
opengl/hellogl/glwidget.cpp

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        ** This file is part of the documentation of the Qt Toolkit.
        **
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    ** as defined by Trolltech AS of Norway and appearing in the file
    ** LICENSE.QPL included in the packaging of this file.
    **
    ** This file may be distributed and/or modified under the terms of the
    ** GNU General Public License version 2 as published by the Free Software
    ** Foundation and appearing in the file LICENSE.GPL included in the
    ** packaging of this file.
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        #include <QtGui>
        #include <QtOpenGL>

        #include <math.h>

        #include "glwidget.h"

        GLWidget::GLWidget(QWidget *parent)
            : QGLWidget(parent)
        {
            object = 0;
            xRot = 0;
            yRot = 0;
            zRot = 0;

            trolltechGreen = QColor::fromCmykF(0.40, 0.0, 1.0, 0.0);
            trolltechPurple = QColor::fromCmykF(0.39, 0.39, 0.0, 0.0);
        }

        GLWidget::~GLWidget()
        {
            makeCurrent();
            glDeleteLists(object, 1);
        }

        QSize GLWidget::minimumSizeHint() const
        {
            return QSize(50, 50);
        }

        QSize GLWidget::sizeHint() const
        {
            return QSize(400, 400);
        }

        void GLWidget::setXRotation(int angle)
        {
            normalizeAngle(&angle);
            if (angle != xRot) {
                xRot = angle;
                emit xRotationChanged(angle);
                updateGL();
            }
        }

        void GLWidget::setYRotation(int angle)
        {
            normalizeAngle(&angle);
            if (angle != yRot) {
                yRot = angle;
                emit yRotationChanged(angle);
                updateGL();
            }
        }

        void GLWidget::setZRotation(int angle)
        {
            normalizeAngle(&angle);
            if (angle != zRot) {
                zRot = angle;
                emit zRotationChanged(angle);
                updateGL();
            }
        }

        void GLWidget::initializeGL()
        {
            qglClearColor(trolltechPurple.dark());
            object = makeObject();
            glShadeModel(GL_FLAT);
            glEnable(GL_DEPTH_TEST);
            glEnable(GL_CULL_FACE);
        }

        void GLWidget::paintGL()
        {
            glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
            glLoadIdentity();
            glTranslated(0.0, 0.0, -10.0);
            glRotated(xRot / 16.0, 1.0, 0.0, 0.0);
            glRotated(yRot / 16.0, 0.0, 1.0, 0.0);
            glRotated(zRot / 16.0, 0.0, 0.0, 1.0);
            glCallList(object);
        }

        void GLWidget::resizeGL(int width, int height)
        {
            int side = qMin(width, height);
            glViewport((width - side) / 2, (height - side) / 2, side, side);

            glMatrixMode(GL_PROJECTION);
            glLoadIdentity();
            glOrtho(-0.5, +0.5, +0.5, -0.5, 4.0, 15.0);
            glMatrixMode(GL_MODELVIEW);
        }

        void GLWidget::mousePressEvent(QMouseEvent *event)
        {
            lastPos = event->pos();
        }

        void GLWidget::mouseMoveEvent(QMouseEvent *event)
        {
            int dx = event->x() - lastPos.x();
            int dy = event->y() - lastPos.y();

            if (event->buttons() & Qt::LeftButton) {
                setXRotation(xRot + 8 * dy);
                setYRotation(yRot + 8 * dx);
            } else if (event->buttons() & Qt::RightButton) {
                setXRotation(xRot + 8 * dy);
                setZRotation(zRot + 8 * dx);
            }
            lastPos = event->pos();
        }

        GLuint GLWidget::makeObject()
        {
            GLuint list = glGenLists(1);
            glNewList(list, GL_COMPILE);

            glBegin(GL_QUADS);

            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;

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

            extrude(x1, y1, x2, y2);
            extrude(x2, y2, y2, x2);
            extrude(y2, x2, y1, x1);
            extrude(y1, x1, x1, y1);
            extrude(x3, y3, x4, y4);
            extrude(x4, y4, y4, x4);
            extrude(y4, x4, y3, x3);

            const double Pi = 3.14159265358979323846;
            const int NumSectors = 200;

            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);

                quad(x5, y5, x6, y6, x7, y7, x8, y8);

                extrude(x6, y6, x7, y7);
                extrude(x8, y8, x5, y5);
            }

            glEnd();

            glEndList();
            return list;
        }

        void GLWidget::quad(GLdouble x1, GLdouble y1, GLdouble x2, GLdouble y2,
                            GLdouble x3, GLdouble y3, GLdouble x4, GLdouble y4)
        {
            qglColor(trolltechGreen);

            glVertex3d(x1, y1, -0.05);
            glVertex3d(x2, y2, -0.05);
            glVertex3d(x3, y3, -0.05);
            glVertex3d(x4, y4, -0.05);

            glVertex3d(x4, y4, +0.05);
            glVertex3d(x3, y3, +0.05);
            glVertex3d(x2, y2, +0.05);
            glVertex3d(x1, y1, +0.05);
        }

        void GLWidget::extrude(GLdouble x1, GLdouble y1, GLdouble x2, GLdouble y2)
        {
            qglColor(trolltechGreen.dark(250 + int(100 * x1)));

            glVertex3d(x1, y1, +0.05);
            glVertex3d(x2, y2, +0.05);
            glVertex3d(x2, y2, -0.05);
            glVertex3d(x1, y1, -0.05);
        }

        void GLWidget::normalizeAngle(int *angle)
        {
            while (*angle < 0)
                *angle += 360 * 16;
            while (*angle > 360 * 16)
                *angle -= 360 * 16;
        }