void TriangleWindow::initialize()
{
        m_program = new QOpenGLShaderProgram(this);
        m_program->addShaderFromSourceCode(QOpenGLShader::Vertex, vertexShaderSource);
        m_program->addShaderFromSourceCode(QOpenGLShader::Fragment, fragmentShaderSource);
        m_program->link();
        m_posAttr = m_program->attributeLocation("posAttr");
        m_colAttr = m_program->attributeLocation("colAttr");
        m_matrixUniform = m_program->uniformLocation("matrix");
}