source: josm/src/org/openstreetmap/josm/data/Preferences.java@ 1

package org.openstreetmap.josm.data;

import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;

import javax.swing.UIManager;
import javax.swing.UIManager.LookAndFeelInfo;

import org.jdom.Element;
import org.jdom.input.SAXBuilder;
import org.jdom.output.Format;
import org.jdom.output.XMLOutputter;
import org.openstreetmap.josm.data.projection.LatitudeLongitude;
import org.openstreetmap.josm.data.projection.Projection;
import org.openstreetmap.josm.data.projection.UTM;


/**
 * This class holds all preferences for JOSM.
 * 
 * @author imi
 */
public class Preferences {

        /**
         * The look and feel. Classname of the look and feel class to use.
         */
        public LookAndFeelInfo laf = UIManager.getInstalledLookAndFeels()[0];

        /**
         * The convertor used to translate lat/lon points to screen points.
         */
        public Projection projection = new UTM();

        /**
         * The monitor geometry in meter per pixel. (How big is 1 pixel in meters)
         * Example: 17" Sony flatscreen in 1280x1024 mode: 0.000264 ppm
         * 
         * Remember: ppm = dpi/25400
         */
        public double ppm = 0.000264;

        
        public static final Projection[] allProjections = new Projection[]{
                new UTM(),
                new LatitudeLongitude()
        };

        /**
         * Return the location of the preferences file
         */
        public static String getPreferencesFile() {
                return System.getProperty("user.home")+"/.josm-preferences";
        }
        
        /**
         * Exception thrown in case of any loading/saving error (including parse errors).
         * @author imi
         */
        public static class PreferencesException extends Exception {
                public PreferencesException(String message, Throwable cause) {
                        super(message, cause);
                }
        }
        /**
         * Load from disk.
         * @throws PreferencesException Any loading error (parse errors as well)
         */
        public void load() throws PreferencesException {
                File file = new File(System.getProperty("user.home")+"/.josm-preferences");
                Element root;
                try {
                        root = new SAXBuilder().build(new FileReader(file)).getRootElement();

                        // laf
                        String lafClassName = root.getChildText("laf");
                        for (LookAndFeelInfo lafInfo : UIManager.getInstalledLookAndFeels())
                                if (lafInfo.getClassName().equals(lafClassName)) {
                                        laf = lafInfo;
                                        break;
                                }
                        if (laf == null)
                                throw new PreferencesException("Look and Feel not found.", null);
                        
                        projection = (Projection)Class.forName(root.getChildText("projection")).newInstance();
                } catch (Exception e) {
                        if (e instanceof PreferencesException)
                                throw (PreferencesException)e;
                        throw new PreferencesException("Could not load preferences", e);
                }
                
        }
        /**
         * Save to disk.
         * @throws PreferencesException Any saving error (exceeding disk space, etc..)
         */
        @SuppressWarnings("unchecked")
        public void save() throws PreferencesException {
                Element root = new Element("josm-settings");
                
                root.getChildren().add(new Element("laf").setText(laf.getClassName()));
                root.getChildren().add(new Element("projection").setText(projection.getClass().getName()));

                try {
                        final FileWriter file = new FileWriter(getPreferencesFile());
                        new XMLOutputter(Format.getPrettyFormat()).output(root, file);
                        file.close();
                } catch (Exception e) {
                        throw new PreferencesException("Could not write preferences", e);
                }
        }
}