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

    /****************************************************************************
    **
    ** 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:
    ** http://www.trolltech.com/products/qt/opensource.html
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    ** review the following information:
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    ** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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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;
    }