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 = getFixedRangeAxisSpace();
        if (fixed != null) {
            if (orientation == PlotOrientation.VERTICAL) {
                space.setLeft(fixed.getLeft());
                space.setRight(fixed.getRight());
            }
            else if (orientation == PlotOrientation.HORIZONTAL) {
                space.setTop(fixed.getTop());
                space.setBottom(fixed.getBottom());                
            }
        }
        else {
            ValueAxis valueAxis = getRangeAxis();
            RectangleEdge valueEdge = Plot.resolveRangeAxisLocation(
                    getRangeAxisLocation(), orientation);
            if (valueAxis != null) {
                space = valueAxis.reserveSpace(g2, this, plotArea, valueEdge, 
                        space);
            }
        }
        
        Rectangle2D adjustedPlotArea = space.shrink(plotArea, null);
        // work out the maximum height or width of the non-shared axes...
        int n = this.subplots.size();

        // calculate plotAreas of all sub-plots, maximum vertical/horizontal 
        // axis width/height
        this.subplotArea = new Rectangle2D[n];
        double x = adjustedPlotArea.getX();
        double y = adjustedPlotArea.getY();
        double usableSize = 0.0;
        if (orientation == PlotOrientation.VERTICAL) {
            usableSize = adjustedPlotArea.getWidth() - this.gap * (n - 1);
        }
        else if (orientation == PlotOrientation.HORIZONTAL) {
            usableSize = adjustedPlotArea.getHeight() - this.gap * (n - 1);
        }

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

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

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

        }

        return space;