function SVGPlotLegend(plot, bgSettings, textSettings) {
    this._plot = plot; // The owning plot
    this._show = true; // Show the legend?
    this._area = [0.9, 0.1, 1.0, 0.9]; // The legend area: left, top, right, bottom,
        // > 1 in pixels, <= 1 as proportion