Axis.java

package org.hihan.girinoscope.ui;

import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.util.ArrayList;
import java.util.List;

public class Axis {

    public static class GraphLabel {

        private String label;

        private Rectangle bounds;

        private GraphLabel(String label) {
            this.label = label;
        }

        public String getLabel() {
            return label;
        }

        public Rectangle getBounds() {
            return bounds;
        }
    }

    private double fraction;

    private List<GraphLabel> graphLabels;

    private Rectangle maxBounds;

    public Axis(double startValue, double endValue, String format) {
        this(startValue, endValue, chooseIncrement(startValue, endValue), format);
    }

    private static double chooseIncrement(double startValue, double endValue) {
        double length = endValue - startValue;
        double increment = Math.pow(10, Math.round(Math.log10(length / 10)));
        double fraction = length / increment;
        if (fraction < 5) {
            increment /= 2;
        }
        if (fraction > 10) {
            increment *= 2;
        }
        return increment;
    }

    public Axis(double startValue, double endValue, double increment, String format) {
        fraction = (endValue - startValue) / increment;
        graphLabels = new ArrayList<Axis.GraphLabel>();
        for (double value = startValue; value <= endValue; value += increment) {
            graphLabels.add(new GraphLabel(String.format(format, value)));
        }
    }

    public void complete(Graphics2D g, Font font) {
        if (maxBounds == null) {
            maxBounds = new Rectangle(0, 0, 0, 0);
            for (GraphLabel graphLabel : graphLabels) {
                if (graphLabel.bounds == null) {
                    graphLabel.bounds = g.getFontMetrics(font).getStringBounds(graphLabel.label, g).getBounds();
                }
                maxBounds = maxBounds.union(graphLabel.bounds);
            }
        }
    }

    public double getFraction() {
        return fraction;
    }

    public GraphLabel[] graphLabels() {
        return graphLabels.toArray(new GraphLabel[0]);
    }

    public Rectangle getMaxBounds() {
        return maxBounds;
    }
}