code: public void setSliderPosition(int y) {
  
          if (y < 0) {
              y = 0;
          }
          if (y > 256) {
              y = 256;
          }
          m_slider.getElement().getStyle().setTop(y - 1047, Unit.PX);
      }
docs: Sets the slider's position on the y-axis.<p>
  @param y Position along the y-axis to set the slider's position to.