source: josm/src/org/openstreetmap/josm/gui/MapStatus.java@ 15

package org.openstreetmap.josm.gui;

import java.awt.AWTEvent;
import java.awt.Point;
import java.awt.Toolkit;
import java.awt.event.AWTEventListener;
import java.awt.event.InputEvent;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
import java.util.Map.Entry;

import javax.swing.BorderFactory;
import javax.swing.BoxLayout;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.Popup;
import javax.swing.PopupFactory;

import org.openstreetmap.josm.data.GeoPoint;
import org.openstreetmap.josm.data.osm.Key;
import org.openstreetmap.josm.data.osm.OsmPrimitive;
import org.openstreetmap.josm.data.osm.visitor.SelectionComponentVisitor;

/**
 * A component that manages some status information display about the map.
 * It keeps a status line below the map up to date and displays some tooltip
 * information if the user hold the mouse long enough at some point.
 * 
 * All this is done in background to not disturb other processes.
 * 
 * The background thread does not alter any data of the map (read only thread).
 * Also it is rather fail safe. In case of some error in the data, it just do
 * nothing instead of whining and complaining.
 * 
 * @author imi
 */
public class MapStatus extends JPanel {

        /**
         * The Layer this status belongs. 
         */
        final Layer mv;
        /**
         * The position of the mouse cursor.
         */
        private JTextField positionText = new JTextField("-000.00000000000000 -000.00000000000000".length());
        /**
         * The field holding the name of the object under the mouse.
         */
        private JTextField nameText = new JTextField(30);
        /**
         * The background thread thats collecting the data.
         */
        private Runnable collector;

        /**
         * The collector class that waits for notification and then update
         * the display objects.
         * 
         * @author imi
         */
        private final class Collector implements Runnable {
                /**
                 * The last object displayed in status line.
                 */
                OsmPrimitive osmStatus;
                /**
                 * A visitor to retrieve name information about the osm primitive
                 */
                private SelectionComponentVisitor visitor = new SelectionComponentVisitor();
                /**
                 * The old modifiers, that was pressed the last time this collector ran.
                 */
                private int oldModifiers;
                /**
                 * The popup displayed to show additional information
                 */
                private Popup popup;

                /**
                 * Execution function for the Collector.
                 */
                public void run() {
                        for (;;) {
                                MouseState ms = new MouseState();
                                synchronized (this) {
                                        try {wait();} catch (InterruptedException e) {}
                                        ms.modifiers = mouseState.modifiers;
                                        ms.mousePos = mouseState.mousePos;
                                }
                                if ((ms.modifiers & MouseEvent.CTRL_DOWN_MASK) != 0 || ms.mousePos == null)
                                        continue; // freeze display when holding down ctrl
                                OsmPrimitive osm = mv.getNearest(ms.mousePos, (ms.modifiers & MouseEvent.ALT_DOWN_MASK) != 0);
                                if (osm == osmStatus && ms.modifiers == oldModifiers)
                                        continue;
                                osmStatus = osm;
                                oldModifiers = ms.modifiers;
                                if (osm != null) {
                                        osm.visit(visitor);
                                        nameText.setText(visitor.name);
                                } else
                                        nameText.setText("");
                                
                                // Popup Information
                                if ((ms.modifiers & MouseEvent.BUTTON2_DOWN_MASK) != 0 && osm != null) {
                                        if (popup != null)
                                                popup.hide();
                                        
                                        StringBuilder text = new StringBuilder("<html>");
                                        text.append(visitor.name);
                                        if (osm.keys != null) {
                                                for (Entry<Key, String> e : osm.keys.entrySet()) {
                                                        text.append("<br>");
                                                        text.append(e.getKey().name);
                                                        text.append("=");
                                                        text.append(e.getValue());
                                                }
                                        }
                                        JLabel l = new JLabel(text.toString(), visitor.icon, JLabel.HORIZONTAL);
                                        
                                        Point p = mv.getLocationOnScreen();
                                        popup = PopupFactory.getSharedInstance().getPopup(mv, l, p.x+ms.mousePos.x+16, p.y+ms.mousePos.y+16);
                                        popup.show();
                                } else if (popup != null) {
                                        popup.hide();
                                        popup = null;
                                }
                        }
                }
        }

        /**
         * Everything, the collector is interested of. Access must be synchronized.
         * @author imi
         */
        class MouseState {
                Point mousePos;
                int modifiers;
        }
        /**
         * The last sent mouse movement event.
         */
        private MouseState mouseState = new MouseState();
        
        /**
         * Construct a new MapStatus and attach it to the Layer.
         * @param mv The Layer the status line is part of.
         */
        public MapStatus(final Layer mv) {
                this.mv = mv;
                
                // Listen for mouse movements and set the position text field
                mv.addMouseMotionListener(new MouseMotionListener(){
                        public void mouseDragged(MouseEvent e) {
                                mouseMoved(e);
                        }
                        public void mouseMoved(MouseEvent e) {
                                // Do not update the view, if ctrl is pressed.
                                if ((e.getModifiersEx() & MouseEvent.CTRL_DOWN_MASK) == 0) {
                                        GeoPoint p = mv.getPoint(e.getX(),e.getY(),true);
                                        positionText.setText(p.lat+" "+p.lon);
                                }
                        }
                });
                
                // Listen to keyboard/mouse events for pressing/releasing alt key and
                // inform the collector.
                Toolkit.getDefaultToolkit().addAWTEventListener(new AWTEventListener(){
                        public void eventDispatched(AWTEvent event) {
                                synchronized (collector) {
                                        mouseState.modifiers = ((InputEvent)event).getModifiersEx();
                                        if (event instanceof MouseEvent)
                                                mouseState.mousePos = ((MouseEvent)event).getPoint();
                                        collector.notify();
                                }
                        }
                }, AWTEvent.KEY_EVENT_MASK | AWTEvent.MOUSE_EVENT_MASK | AWTEvent.MOUSE_MOTION_EVENT_MASK);

                positionText.setEditable(false);
                nameText.setEditable(false);
                setLayout(new BoxLayout(this, BoxLayout.X_AXIS));
                setBorder(BorderFactory.createEmptyBorder(5,5,5,5));
                add(new JLabel("Lat/Lon "));
                add(positionText);
                add(new JLabel(" Object "));
                add(nameText);

                // The background thread
                collector = new Collector();
                new Thread(collector).start();
        }
}