update() function is not working in qopenlwidget properly

[Md Saif Khan]

I am new in qt platform. Here i have added my code. I trying to use mouse functionalities. I have added Slot and signal in my code. In slot, i have added update() function to update while i change something. Whenever i use update() function, the qopenglwidget window do not show anything which is drawn .

MyOpenglWidget::MyOpenglWidget(QWidget *parent) : QOpenGLWidget(parent)
{
    setFormat(QSurfaceFormat::defaultFormat());

}
void MyOpenglWidget::initializeGL()
{
    initializeOpenGLFunctions(); // obvious

        buffer = QOpenGLBuffer(QOpenGLBuffer::VertexBuffer);
        buffer.setUsagePattern(QOpenGLBuffer::StaticDraw);
        Q_ASSERT(buffer.create());
        Q_ASSERT(buffer.bind());

        shaderProg.addShaderFromSourceCode(QOpenGLShader::Vertex, vertexShaderSource);
        shaderProg.addShaderFromSourceCode(QOpenGLShader::Fragment, fragmentShaderSource);
        Q_ASSERT(shaderProg.link());

        m_MVPMatrixLoc = shaderProg.uniformLocation("MVP");
        Q_ASSERT(shaderProg.bind());

        const int vPosition = 0;

        glVertexAttribPointer(vPosition, 3, GL_FLOAT, GL_FALSE, 0, NULL);

        glEnableVertexAttribArray(vPosition);




}

void MyOpenglWidget::paintGL()
{
  QTextStream cout(stdout);
  glClear(GL_COLOR_BUFFER_BIT);

  glClearColor(1.0, 1.0, 1.0, 1.0);
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  glEnable(GL_DEPTH_TEST);
  glDepthFunc(GL_LESS);


  shaderProg.enableAttributeArray("vPosition");

  modelMatrix.setToIdentity();

  mvp = projectionMatrix * viewMatrix * modelMatrix;

  shaderProg.setUniformValue(m_MVPMatrixLoc, mvp);

  viewMatrix.lookAt(
              QVector3D(x, y, z), // Camera is at (x,y,z), in World Space
              QVector3D(x, y, 0), // and looks at (x,y)
              QVector3D(0, 1, 0)  // Head is up (set to 0,-1,0 to look upside-down)
              );



    for(unsigned int i=0;i<vec.size();i++){
        for(unsigned int j=0;j<vec[i].size();j++){
            buffer.allocate( vec[i].size() *sizeof (GLfloat));
            buffer.write(0, &vec[i][0], vec[i].size() *sizeof (GLfloat));
            glDrawArrays(GL_LINE_STRIP, 0, vec[i].size()/3);
            //cout<<i<<" "<<j<<" "<<vec[i].size()<<" \n";
        }
    }


    glFlush();

}


void MyOpenglWidget::resizeGL(int w, int h)
{
      Q_UNUSED(w); Q_UNUSED(h);
      glViewport(0, 0, (GLint)width(), (GLint)height());
      projectionMatrix.perspective(45.0f, (float)w/(float)h, z, z/1000);
}

void MyOpenglWidget::mousePressEvent(QMouseEvent *event)
{
    m_lastPos = event->pos();
}

void MyOpenglWidget::mouseMoveEvent(QMouseEvent *event)
{
    int dx = event->position().x() - m_lastPos.x();
    int dy = event->position().y() - m_lastPos.y();

    if (event->buttons() & Qt::LeftButton) {
        setZRotation(m_zRot + 8 * dx);
    } 
    m_lastPos = event->pos();
}

void MyOpenglWidget::setZRotation(int angle) // slot
{
    qNormalizeAngle(angle);
    if (angle != m_zRot) {
        m_zRot = angle;
        emit zRotationChanged(angle);
        update();
        qDebug()<< m_zRot;
    }
}

[SGaist]

Hi,

You should take a look at the Hello GL 2 example to get started.