glwidget.cpp Example File
^{opengl/textures/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
    **
    ** 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 <math.h>

    #include "glwidget.h"

    GLuint GLWidget::sharedObject = 0;
    int GLWidget::refCount = 0;

    GLWidget::GLWidget(QWidget *parent, QGLWidget *shareWidget)
        : QGLWidget(parent, shareWidget)
    {
        clearColor = Qt::black;
        xRot = 0;
        yRot = 0;
        zRot = 0;
    }

    GLWidget::~GLWidget()
    {
        if (--refCount == 0) {
            makeCurrent();
            glDeleteLists(sharedObject, 1);
        }
    }

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

    QSize GLWidget::sizeHint() const
    {
        return QSize(200, 200);
    }

    void GLWidget::rotateBy(int xAngle, int yAngle, int zAngle)
    {
        xRot += xAngle;
        yRot += yAngle;
        zRot += zAngle;
        updateGL();
    }

    void GLWidget::setClearColor(const QColor &color)
    {
        clearColor = color;
        updateGL();
    }

    void GLWidget::initializeGL()
    {
        if (!sharedObject)
            sharedObject = makeObject();
        ++refCount;

        glEnable(GL_DEPTH_TEST);
        glEnable(GL_CULL_FACE);
        glEnable(GL_TEXTURE_2D);
    }

    void GLWidget::paintGL()
    {
        qglClearColor(clearColor);
        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(sharedObject);
    }

    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) {
            rotateBy(8 * dy, 8 * dx, 0);
        } else if (event->buttons() & Qt::RightButton) {
            rotateBy(8 * dy, 0, 8 * dx);
        }
        lastPos = event->pos();
    }

    void GLWidget::mouseReleaseEvent(QMouseEvent * /* event */)
    {
        emit clicked();
    }

    GLuint GLWidget::makeObject()
    {
        static const int coords[6][4][3] = {
            { { +1, -1, -1 }, { -1, -1, -1 }, { -1, +1, -1 }, { +1, +1, -1 } },
            { { +1, +1, -1 }, { -1, +1, -1 }, { -1, +1, +1 }, { +1, +1, +1 } },
            { { +1, -1, +1 }, { +1, -1, -1 }, { +1, +1, -1 }, { +1, +1, +1 } },
            { { -1, -1, -1 }, { -1, -1, +1 }, { -1, +1, +1 }, { -1, +1, -1 } },
            { { +1, -1, +1 }, { -1, -1, +1 }, { -1, -1, -1 }, { +1, -1, -1 } },
            { { -1, -1, +1 }, { +1, -1, +1 }, { +1, +1, +1 }, { -1, +1, +1 } }
        };

        GLuint textures[6];
        for (int j=0; j < 6; ++j)
            textures[j] = bindTexture(QPixmap(QString(":/images/side%1.png").arg(j + 1)),
                                      GL_TEXTURE_2D);

        GLuint list = glGenLists(1);
        glNewList(list, GL_COMPILE);
        for (int i = 0; i < 6; ++i) {
            glBindTexture(GL_TEXTURE_2D, textures[i]);
            glBegin(GL_QUADS);
            for (int j = 0; j < 4; ++j) {
                glTexCoord2d(j == 0 || j == 3, j == 0 || j == 1);
                glVertex3d(0.2 * coords[i][j][0], 0.2 * coords[i][j][1],
                           0.2 * coords[i][j][2]);
            }
            glEnd();
        }

        glEndList();
        return list;
    }