source: josm/src/org/openstreetmap/josm/data/osm/visitor/SimplePaintVisitor.java@ 93

package org.openstreetmap.josm.data.osm.visitor;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Point;

import org.openstreetmap.josm.Main;
import org.openstreetmap.josm.data.osm.Node;
import org.openstreetmap.josm.data.osm.Segment;
import org.openstreetmap.josm.data.osm.Way;
import org.openstreetmap.josm.gui.NavigatableComponent;
import org.openstreetmap.josm.tools.ColorHelper;

/**
 * A visitor that paint a simple scheme of every primitive it visits to a 
 * previous set graphic environment.
 * 
 * @author imi
 */
public class SimplePaintVisitor implements Visitor {

        public final static Color darkerblue = new Color(0,0,96);
        public final static Color darkblue = new Color(0,0,128);
        public final static Color darkgreen = new Color(0,128,0);

        /**
         * The environment to paint to.
         */
        private final Graphics g;
        /**
         * MapView to get screen coordinates.
         */
        private final NavigatableComponent nc;
        private static final double PHI = Math.toRadians(20);

        /**
         * Construct the painter visitor.
         * @param g   The graphics to draw to.
         * @param mv  The view to get screen coordinates from.
         */
        public SimplePaintVisitor(Graphics g, NavigatableComponent mv) {
                this.g = g;
                this.nc = mv;
        }

        /**
         * Draw a small rectangle. 
         * White if selected (as always) or red otherwise.
         * 
         * @param n The node to draw.
         */
        public void visit(Node n) {
                drawNode(n, n.selected ? getPreferencesColor("selected", Color.WHITE)
                                : getPreferencesColor("node", Color.RED));
        }

        /**
         * Draw just a line between the points.
         * White if selected (as always) or green otherwise.
         */
        public void visit(Segment ls) {
                drawSegment(ls, getPreferencesColor("segment", darkgreen));
        }

        /**
         * Draw a darkblue line for all segments.
         * @param w The way to draw.
         */
        public void visit(Way w) {
                // only to overwrite with blue
                Color wayColor = getPreferencesColor("way", darkblue);
                for (Segment ls : w.segments) {
                        if (ls.incomplete) {
                                wayColor = getPreferencesColor("incomplete way", darkerblue);
                                break;
                        }
                }

                for (Segment ls : w.segments)
                        if (!ls.selected) // selected already in good color
                                drawSegment(ls, w.selected ? getPreferencesColor("selected", Color.WHITE) : wayColor);
        }

        /**
         * Draw the node as small rectangle with the given color.
         *
         * @param n             The node to draw.
         * @param color The color of the node.
         */
        private void drawNode(Node n, Color color) {
                Point p = nc.getPoint(n.eastNorth);
                g.setColor(color);
                g.drawRect(p.x-1, p.y-1, 2, 2);
        }

        /**
         * Draw a line with the given color.
         */
        private void drawSegment(Segment ls, Color col) {
                if (ls.incomplete)
                        return;
                if (ls.selected)
                        col = getPreferencesColor("selected", Color.WHITE);
                g.setColor(col);
                Point p1 = nc.getPoint(ls.from.eastNorth);
                Point p2 = nc.getPoint(ls.to.eastNorth);
                g.drawLine(p1.x, p1.y, p2.x, p2.y);

                if (Main.pref.getBoolean("draw.segment.direction")) {
                        double t = Math.atan2(p2.y-p1.y, p2.x-p1.x) + Math.PI;
                g.drawLine(p2.x,p2.y, (int)(p2.x + 10*Math.cos(t-PHI)), (int)(p2.y + 10*Math.sin(t-PHI)));
                g.drawLine(p2.x,p2.y, (int)(p2.x + 10*Math.cos(t+PHI)), (int)(p2.y + 10*Math.sin(t+PHI)));
                }
        }

        public static Color getPreferencesColor(String colName, Color def) {
                String colStr = Main.pref.get("color."+colName);
                if (colStr.equals(""))
                        return def;
                return ColorHelper.html2color(colStr);
        }
}