docs: private void initializePlot() {
      plot = new VisualizationPlot();
      { // Add a background element:
        CSSClass cls = new CSSClass(this, "background");
        final String bgcol = context.getStyleLibrary().getBackgroundColor(StyleLibrary.PAGE);
        cls.setStatement(SVGConstants.CSS_FILL_PROPERTY, bgcol);
        plot.addCSSClassOrLogError(cls);
        Element background = plot.svgElement(SVGConstants.SVG_RECT_TAG);
        background.setAttribute(SVGConstants.SVG_X_ATTRIBUTE, "0");
        background.setAttribute(SVGConstants.SVG_Y_ATTRIBUTE, "0");
        background.setAttribute(SVGConstants.SVG_WIDTH_ATTRIBUTE, "100%");
        background.setAttribute(SVGConstants.SVG_HEIGHT_ATTRIBUTE, "100%");
        SVGUtil.setCSSClass(background, cls.getName());
        // Don't export a white background:
        if("white".equals(bgcol)) {
          background.setAttribute(SVGPlot.NO_EXPORT_ATTRIBUTE, SVGPlot.NO_EXPORT_ATTRIBUTE);
        }
        plot.getRoot().appendChild(background);
      }
      { // setup the hover CSS classes.
        selcss = new CSSClass(this, "s");
        if(DEBUG_LAYOUT) {
          selcss.setStatement(SVGConstants.CSS_STROKE_PROPERTY, SVGConstants.CSS_RED_VALUE);
          selcss.setStatement(SVGConstants.CSS_STROKE_WIDTH_PROPERTY, .00001 * StyleLibrary.SCALE);
          selcss.setStatement(SVGConstants.CSS_STROKE_OPACITY_PROPERTY, "0.5");
        }
        selcss.setStatement(SVGConstants.CSS_FILL_PROPERTY, SVGConstants.CSS_RED_VALUE);
        selcss.setStatement(SVGConstants.CSS_FILL_OPACITY_PROPERTY, "0");
        selcss.setStatement(SVGConstants.CSS_CURSOR_PROPERTY, SVGConstants.CSS_POINTER_VALUE);
        plot.addCSSClassOrLogError(selcss);
        CSSClass hovcss = new CSSClass(this, "h");
        hovcss.setStatement(SVGConstants.CSS_FILL_OPACITY_PROPERTY, "0.25");
        plot.addCSSClassOrLogError(hovcss);
        // Hover listener.
        hoverer = new CSSHoverClass(hovcss.getName(), null, true);
      }
  
      // Disable Batik default interactions (zoom, rotate, etc.)
      if(single) {
        plot.setDisableInteractions(true);
      }
      SVGEffects.addShadowFilter(plot);
      SVGEffects.addLightGradient(plot);
    }