protected AxisSpace calculateAxisSpace(Graphics2D g2,
                                           Rectangle2D plotArea) {

        AxisSpace space = new AxisSpace();
        PlotOrientation orientation = getOrientation();

        // work out the space required by the domain axis...
        AxisSpace fixed = getFixedDomainAxisSpace();
        if (fixed != null) {
            if (orientation == PlotOrientation.HORIZONTAL) {
                space.setLeft(fixed.getLeft());
                space.setRight(fixed.getRight());
            }
            else if (orientation == PlotOrientation.VERTICAL) {
                space.setTop(fixed.getTop());
                space.setBottom(fixed.getBottom());
            }
        }
        else {
            ValueAxis xAxis = getDomainAxis();
            RectangleEdge xEdge = Plot.resolveDomainAxisLocation(
                    getDomainAxisLocation(), orientation);
            if (xAxis != null) {
                space = xAxis.reserveSpace(g2, this, plotArea, xEdge, space);
            }
        }

        Rectangle2D adjustedPlotArea = space.shrink(plotArea, null);

        // work out the maximum height or width of the non-shared axes...
        int n = this.subplots.size();
        this.subplotAreas = new Rectangle2D[n];
        double x = adjustedPlotArea.getX();
        double y = adjustedPlotArea.getY();
        double usableSize = 0.0;
        if (orientation == PlotOrientation.HORIZONTAL) {
            usableSize = adjustedPlotArea.getWidth() - this.gap * (n - 1);
        }
        else if (orientation == PlotOrientation.VERTICAL) {
            usableSize = adjustedPlotArea.getHeight() - this.gap * (n - 1);
        }

        for (int i = 0; i < n; i++) {
            XYPlot plot = (XYPlot) this.subplots.get(i);

            // calculate sub-plot area
            if (orientation == PlotOrientation.HORIZONTAL) {
                double w = usableSize * plot.getWeight() / this.totalWeight;
                this.subplotAreas[i] = new Rectangle2D.Double(x, y, w,
                        adjustedPlotArea.getHeight());
                x = x + w + this.gap;
            }
            else if (orientation == PlotOrientation.VERTICAL) {
                double h = usableSize * plot.getWeight() / this.totalWeight;
                this.subplotAreas[i] = new Rectangle2D.Double(x, y,
                        adjustedPlotArea.getWidth(), h);
                y = y + h + this.gap;
            }

            AxisSpace subSpace = plot.calculateRangeAxisSpace(g2,
                    this.subplotAreas[i], null);
            space.ensureAtLeast(subSpace);

        }

        return space;