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

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     #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;
     }