docs: private void addBackground(VisualizerContext context) {
      // Make a background
      CSSClass cls = new CSSClass(this, "background");
      cls.setStatement(SVGConstants.CSS_FILL_PROPERTY, context.getStyleLibrary().getBackgroundColor(StyleLibrary.PAGE));
      addCSSClassOrLogError(cls);
      Element bg = this.svgElement(SVGConstants.SVG_RECT_TAG, cls.getName());
      SVGUtil.setAtt(bg, SVGConstants.SVG_X_ATTRIBUTE, "0");
      SVGUtil.setAtt(bg, SVGConstants.SVG_Y_ATTRIBUTE, "0");
      SVGUtil.setAtt(bg, SVGConstants.SVG_WIDTH_ATTRIBUTE, "100%");
      SVGUtil.setAtt(bg, SVGConstants.SVG_HEIGHT_ATTRIBUTE, "100%");
      SVGUtil.setAtt(bg, NO_EXPORT_ATTRIBUTE, NO_EXPORT_ATTRIBUTE);
  
      // Note that we rely on this being called before any other drawing routines.
      getRoot().appendChild(bg);
    }