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

        /****************************************************************************
        **
        ** Copyright (C) 2006-2006 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
        **
        ** If you are unsure which license is appropriate for your use, please
        ** review the following information:
        ** http://www.trolltech.com/products/qt/licensing.html or contact the
        ** sales department at sales@trolltech.com.
        **
        ** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
        ** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
        **
        ****************************************************************************/

        #include <QtGui>
        #include <QtOpenGL>
        #include <stdlib.h>

        #include <math.h>

        #include "bubble.h"
        #include "glwidget.h"

        GLWidget::GLWidget(QWidget *parent)
            : QGLWidget(QGLFormat(QGL::SampleBuffers), parent)
        {
            QTime midnight(0, 0, 0);
            srand(midnight.secsTo(QTime::currentTime()));

            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);

            animationTimer.setSingleShot(false);
            connect(&animationTimer, SIGNAL(timeout()), this, SLOT(animate()));
            animationTimer.start(25);

            setAttribute(Qt::WA_NoSystemBackground);
            setMinimumSize(200, 200);
            setWindowTitle(tr("Overpainting a Scene"));
        }

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

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

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

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

        void GLWidget::initializeGL()
        {
            object = makeObject();
        }

        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();
        }

        void GLWidget::paintEvent(QPaintEvent *event)
        {
            QPainter painter;
            painter.begin(this);
            painter.setRenderHint(QPainter::Antialiasing);

            glPushAttrib(GL_ALL_ATTRIB_BITS);
            glMatrixMode(GL_PROJECTION);
            glPushMatrix();
            glMatrixMode(GL_MODELVIEW);
            glPushMatrix();

            qglClearColor(trolltechPurple.dark());
            glShadeModel(GL_SMOOTH);
            glEnable(GL_DEPTH_TEST);
            glEnable(GL_CULL_FACE);
            glEnable(GL_LIGHTING);
            glEnable(GL_LIGHT0);
            static GLfloat lightPosition[4] = { 0.5, 5.0, 7.0, 1.0 };
            glLightfv(GL_LIGHT0, GL_POSITION, lightPosition);

            resizeGL(width(), height());

            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);

            glPopAttrib();
            glMatrixMode(GL_MODELVIEW);
            glPopMatrix();
            glMatrixMode(GL_PROJECTION);
            glPopMatrix();

            glDisable(GL_CULL_FACE); // ### not required if begin() also does it

            foreach (Bubble *bubble, bubbles) {
                if (bubble->rect().intersects(event->rect()))
                    bubble->drawBubble(&painter);
            }

            painter.drawImage((width() - image.width())/2, 0, image);
            painter.end();
        }

        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);

            formatInstructions(width, height);
        }

        void GLWidget::showEvent(QShowEvent *event)
        {
            Q_UNUSED(event);
            createBubbles(20 - bubbles.count());
        }

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

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

            glEnable(GL_NORMALIZE);
            glBegin(GL_QUADS);

            static GLfloat logoDiffuseColor[4] = {trolltechGreen.red()/255.0,
                                                  trolltechGreen.green()/255.0,
                                                  trolltechGreen.blue()/255.0, 1.0};
            glMaterialfv(GL_FRONT, GL_DIFFUSE, logoDiffuseColor);

            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)
        {
            glNormal3d(0.0, 0.0, -1.0);
            glVertex3d(x1, y1, -0.05);
            glVertex3d(x2, y2, -0.05);
            glVertex3d(x3, y3, -0.05);
            glVertex3d(x4, y4, -0.05);

            glNormal3d(0.0, 0.0, 1.0);
            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)));

            glNormal3d((x1 + x2)/2.0, (y1 + y2)/2.0, 0.0);
            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;
        }

        void GLWidget::createBubbles(int number)
        {
            for (int i = 0; i < number; ++i) {
                QPointF position(width()*(0.1 + (0.8*rand()/(RAND_MAX+1.0))),
                                height()*(0.1 + (0.8*rand()/(RAND_MAX+1.0))));
                qreal radius = qMin(width(), height())*(0.0125 + 0.0875*rand()/(RAND_MAX+1.0));
                QPointF velocity(width()*0.0125*(-0.5 + rand()/(RAND_MAX+1.0)),
                                height()*0.0125*(-0.5 + rand()/(RAND_MAX+1.0)));

                bubbles.append(new Bubble(position, radius, velocity));
            }
        }

        void GLWidget::animate()
        {
            QMutableListIterator<Bubble*> iter(bubbles);

            while (iter.hasNext()) {
                Bubble *bubble = iter.next();
                update(bubble->rect().toRect());
                bubble->move(rect());
                update(bubble->rect().toRect());
            }
        }

        void GLWidget::formatInstructions(int width, int height)
        {
            QString text = tr("Click and drag with the left mouse button "
                              "to rotate the Qt logo.");
            QFontMetrics metrics = QFontMetrics(font());
            int border = qMax(4, metrics.leading());

            QRect rect = metrics.boundingRect(0, 0, width - 2*border, int(height*0.125),
                Qt::AlignCenter | Qt::TextWordWrap, text);
            image = QImage(width, rect.height() + 2*border, QImage::Format_ARGB32_Premultiplied);
            image.fill(qRgba(0, 0, 0, 127));

            QPainter painter;
            painter.begin(&image);
            painter.setRenderHint(QPainter::TextAntialiasing);
            painter.setPen(Qt::white);
            painter.drawText((width - rect.width())/2, border,
                             rect.width(), rect.height(),
                             Qt::AlignCenter | Qt::TextWordWrap, text);
            painter.end();
        }