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

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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]));
         }
     }
 }