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

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     ** General Public License version 2.1 as published by the Free Software
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     ** packaging of this file.  Please review the following information to
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     ** Alternatively, this file may be used under the terms of the GNU
     ** General Public License version 3.0 as published by the Free Software
     ** Foundation and appearing in the file LICENSE.GPL included in the
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     #include <QtGui>
     #include <QtOpenGL>

     #include "glwidget.h"

     GLWidget::GLWidget(QWidget *parent, QGLWidget *shareWidget)
         : QGLWidget(parent, shareWidget)
     {
         clearColor = Qt::black;
         xRot = 0;
         yRot = 0;
         zRot = 0;
     #ifdef QT_OPENGL_ES_2
         program = 0;
     #endif
     }

     GLWidget::~GLWidget()
     {
     }

     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()
     {
         makeObject();

         glEnable(GL_DEPTH_TEST);
         glEnable(GL_CULL_FACE);
     #ifndef QT_OPENGL_ES_2
         glEnable(GL_TEXTURE_2D);
     #endif

     #ifdef QT_OPENGL_ES_2

     #define PROGRAM_VERTEX_ATTRIBUTE 0
     #define PROGRAM_TEXCOORD_ATTRIBUTE 1

         QGLShader *vshader = new QGLShader(QGLShader::Vertex, this);
         const char *vsrc =
             "attribute highp vec4 vertex;\n"
             "attribute mediump vec4 texCoord;\n"
             "varying mediump vec4 texc;\n"
             "uniform mediump mat4 matrix;\n"
             "void main(void)\n"
             "{\n"
             "    gl_Position = matrix * vertex;\n"
             "    texc = texCoord;\n"
             "}\n";
         vshader->compileSourceCode(vsrc);

         QGLShader *fshader = new QGLShader(QGLShader::Fragment, this);
         const char *fsrc =
             "uniform sampler2D texture;\n"
             "varying mediump vec4 texc;\n"
             "void main(void)\n"
             "{\n"
             "    gl_FragColor = texture2D(texture, texc.st);\n"
             "}\n";
         fshader->compileSourceCode(fsrc);

         program = new QGLShaderProgram(this);
         program->addShader(vshader);
         program->addShader(fshader);
         program->bindAttributeLocation("vertex", PROGRAM_VERTEX_ATTRIBUTE);
         program->bindAttributeLocation("texCoord", PROGRAM_TEXCOORD_ATTRIBUTE);
         program->link();

         program->bind();
         program->setUniformValue("texture", 0);

     #endif
     }

     void GLWidget::paintGL()
     {
         qglClearColor(clearColor);
         glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

     #if !defined(QT_OPENGL_ES_2)

         glLoadIdentity();
         glTranslatef(0.0f, 0.0f, -10.0f);
         glRotatef(xRot / 16.0f, 1.0f, 0.0f, 0.0f);
         glRotatef(yRot / 16.0f, 0.0f, 1.0f, 0.0f);
         glRotatef(zRot / 16.0f, 0.0f, 0.0f, 1.0f);

         glVertexPointer(3, GL_FLOAT, 0, vertices.constData());
         glTexCoordPointer(2, GL_FLOAT, 0, texCoords.constData());
         glEnableClientState(GL_VERTEX_ARRAY);
         glEnableClientState(GL_TEXTURE_COORD_ARRAY);

     #else

         QMatrix4x4 m;
         m.ortho(-0.5f, +0.5f, +0.5f, -0.5f, 4.0f, 15.0f);
         m.translate(0.0f, 0.0f, -10.0f);
         m.rotate(xRot / 16.0f, 1.0f, 0.0f, 0.0f);
         m.rotate(yRot / 16.0f, 0.0f, 1.0f, 0.0f);
         m.rotate(zRot / 16.0f, 0.0f, 0.0f, 1.0f);

         program->setUniformValue("matrix", m);
         program->enableAttributeArray(PROGRAM_VERTEX_ATTRIBUTE);
         program->enableAttributeArray(PROGRAM_TEXCOORD_ATTRIBUTE);
         program->setAttributeArray
             (PROGRAM_VERTEX_ATTRIBUTE, vertices.constData());
         program->setAttributeArray
             (PROGRAM_TEXCOORD_ATTRIBUTE, texCoords.constData());

     #endif

         for (int i = 0; i < 6; ++i) {
             glBindTexture(GL_TEXTURE_2D, textures[i]);
             glDrawArrays(GL_TRIANGLE_FAN, i * 4, 4);
         }
     }

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

     #if !defined(QT_OPENGL_ES_2)
         glMatrixMode(GL_PROJECTION);
         glLoadIdentity();
     #ifndef QT_OPENGL_ES
         glOrtho(-0.5, +0.5, +0.5, -0.5, 4.0, 15.0);
     #else
         glOrthof(-0.5, +0.5, +0.5, -0.5, 4.0, 15.0);
     #endif
         glMatrixMode(GL_MODELVIEW);
     #endif
     }

     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();
     }

     void 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 } }
         };

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

         for (int i = 0; i < 6; ++i) {
             for (int j = 0; j < 4; ++j) {
                 texCoords.append
                     (QVector2D(j == 0 || j == 3, j == 0 || j == 1));
                 vertices.append
                     (QVector3D(0.2 * coords[i][j][0], 0.2 * coords[i][j][1],
                                0.2 * coords[i][j][2]));
             }
         }
     }