JMapViewer.java

package org.openstreetmap.gui.jmapviewer;

//License: GPL. Copyright 2008 by Jan Peter Stotz

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.Insets;
import java.awt.Point;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;
import java.awt.font.TextAttribute;
import java.awt.geom.Rectangle2D;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;

import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JPanel;
import javax.swing.JSlider;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

import org.openstreetmap.gui.jmapviewer.interfaces.MapMarker;
import org.openstreetmap.gui.jmapviewer.interfaces.MapRectangle;
import org.openstreetmap.gui.jmapviewer.interfaces.TileCache;
import org.openstreetmap.gui.jmapviewer.interfaces.TileLoader;
import org.openstreetmap.gui.jmapviewer.interfaces.TileLoaderListener;
import org.openstreetmap.gui.jmapviewer.interfaces.TileSource;
import org.openstreetmap.gui.jmapviewer.tilesources.OsmTileSource;

/**
 * 
 * Provides a simple panel that displays pre-rendered map tiles loaded from the
 * OpenStreetMap project.
 * 
 * @author Jan Peter Stotz
 * 
 */
public class JMapViewer extends JPanel implements TileLoaderListener {

    private static final long serialVersionUID = 1L;

    /**
     * Vectors for clock-wise tile painting
     */
    protected static final Point[] move = { new Point(1, 0), new Point(0, 1), new Point(-1, 0), new Point(0, -1) };

    public static final int MAX_ZOOM = 22;
    public static final int MIN_ZOOM = 0;

    protected List<MapMarker> mapMarkerList;
    protected List<MapRectangle> mapRectangleList;

    protected boolean mapMarkersVisible;
    protected boolean mapRectanglesVisible;

    protected boolean tileGridVisible;

    protected TileController tileController;

    /**
     * x- and y-position of the center of this map-panel on the world map
     * denoted in screen pixel regarding the current zoom level.
     */
    protected Point center;

    /**
     * Current zoom level
     */
    protected int zoom;

    protected JSlider zoomSlider;
    protected JButton zoomInButton;
    protected JButton zoomOutButton;

    private TileSource tileSource;

    // Attribution
    private Image attrImage;
    private String attrTermsUrl;
    public static final Font ATTR_FONT = new Font("Arial", Font.PLAIN, 10);
    public static final Font ATTR_LINK_FONT;

    static {
        HashMap<TextAttribute, Integer> aUnderline = new HashMap<TextAttribute, Integer>();
        aUnderline.put(TextAttribute.UNDERLINE, TextAttribute.UNDERLINE_ON);
        ATTR_LINK_FONT = ATTR_FONT.deriveFont(aUnderline);
    }

    /**
     * Creates a standard {@link JMapViewer} instance that can be controlled via
     * mouse: hold right mouse button for moving, double click left mouse button
     * or use mouse wheel for zooming. Loaded tiles are stored the
     * {@link MemoryTileCache} and the tile loader uses 4 parallel threads for
     * retrieving the tiles.
     */
    public JMapViewer() {
        this(new MemoryTileCache(), 4);
        new DefaultMapController(this);
    }

    public JMapViewer(TileCache tileCache, int downloadThreadCount) {
        super();
        tileSource = new OsmTileSource.Mapnik();
        tileController = new TileController(tileSource, tileCache, this);
        mapMarkerList = new LinkedList<MapMarker>();
        mapRectangleList = new LinkedList<MapRectangle>();
        mapMarkersVisible = true;
        mapRectanglesVisible = true;
        tileGridVisible = false;
        setLayout(null);
        initializeZoomSlider();
        setMinimumSize(new Dimension(tileSource.getTileSize(), tileSource.getTileSize()));
        setPreferredSize(new Dimension(400, 400));
        setDisplayPositionByLatLon(50, 9, 3);
        //setToolTipText("");
    }

    @Override
    public String getToolTipText(MouseEvent event) {
        //        Point screenPoint = event.getLocationOnScreen();
        //        Coordinate c = getPosition(screenPoint);
        return super.getToolTipText(event);
    }

    protected void initializeZoomSlider() {
        zoomSlider = new JSlider(MIN_ZOOM, tileController.getTileSource().getMaxZoom());
        zoomSlider.setOrientation(JSlider.VERTICAL);
        zoomSlider.setBounds(10, 10, 30, 150);
        zoomSlider.setOpaque(false);
        zoomSlider.addChangeListener(new ChangeListener() {
            public void stateChanged(ChangeEvent e) {
                setZoom(zoomSlider.getValue());
            }
        });
        add(zoomSlider);
        int size = 18;
        try {
            ImageIcon icon = new ImageIcon(getClass().getResource("images/plus.png"));
            zoomInButton = new JButton(icon);
        } catch (Exception e) {
            zoomInButton = new JButton("+");
            zoomInButton.setFont(new Font("sansserif", Font.BOLD, 9));
            zoomInButton.setMargin(new Insets(0, 0, 0, 0));
        }
        zoomInButton.setBounds(4, 155, size, size);
        zoomInButton.addActionListener(new ActionListener() {

            public void actionPerformed(ActionEvent e) {
                zoomIn();
            }
        });
        add(zoomInButton);
        try {
            ImageIcon icon = new ImageIcon(getClass().getResource("images/minus.png"));
            zoomOutButton = new JButton(icon);
        } catch (Exception e) {
            zoomOutButton = new JButton("-");
            zoomOutButton.setFont(new Font("sansserif", Font.BOLD, 9));
            zoomOutButton.setMargin(new Insets(0, 0, 0, 0));
        }
        zoomOutButton.setBounds(8 + size, 155, size, size);
        zoomOutButton.addActionListener(new ActionListener() {

            public void actionPerformed(ActionEvent e) {
                zoomOut();
            }
        });
        add(zoomOutButton);
    }

    /**
     * Changes the map pane so that it is centered on the specified coordinate
     * at the given zoom level.
     * 
     * @param lat
     *            latitude of the specified coordinate
     * @param lon
     *            longitude of the specified coordinate
     * @param zoom
     *            {@link #MIN_ZOOM} <= zoom level <= {@link #MAX_ZOOM}
     */
    public void setDisplayPositionByLatLon(double lat, double lon, int zoom) {
        setDisplayPositionByLatLon(new Point(getWidth() / 2, getHeight() / 2), lat, lon, zoom);
    }

    /**
     * Changes the map pane so that the specified coordinate at the given zoom
     * level is displayed on the map at the screen coordinate
     * <code>mapPoint</code>.
     * 
     * @param mapPoint
     *            point on the map denoted in pixels where the coordinate should
     *            be set
     * @param lat
     *            latitude of the specified coordinate
     * @param lon
     *            longitude of the specified coordinate
     * @param zoom
     *            {@link #MIN_ZOOM} <= zoom level <=
     *            {@link TileSource#getMaxZoom()}
     */
    public void setDisplayPositionByLatLon(Point mapPoint, double lat, double lon, int zoom) {
        int x = OsmMercator.LonToX(lon, zoom);
        int y = OsmMercator.LatToY(lat, zoom);
        setDisplayPosition(mapPoint, x, y, zoom);
    }

    public void setDisplayPosition(int x, int y, int zoom) {
        setDisplayPosition(new Point(getWidth() / 2, getHeight() / 2), x, y, zoom);
    }

    public void setDisplayPosition(Point mapPoint, int x, int y, int zoom) {
        if (zoom > tileController.getTileSource().getMaxZoom() || zoom < MIN_ZOOM)
            return;

        // Get the plain tile number
        Point p = new Point();
        p.x = x - mapPoint.x + getWidth() / 2;
        p.y = y - mapPoint.y + getHeight() / 2;
        center = p;
        setIgnoreRepaint(true);
        try {
            int oldZoom = this.zoom;
            this.zoom = zoom;
            if (oldZoom != zoom) {
                zoomChanged(oldZoom);
            }
            if (zoomSlider.getValue() != zoom) {
                zoomSlider.setValue(zoom);
            }
        } finally {
            setIgnoreRepaint(false);
            repaint();
        }
    }

    /**
     * Sets the displayed map pane and zoom level so that all map markers are
     * visible.
     */
    public void setDisplayToFitMapMarkers() {
        if (mapMarkerList == null || mapMarkerList.size() == 0)
            return;
        int x_min = Integer.MAX_VALUE;
        int y_min = Integer.MAX_VALUE;
        int x_max = Integer.MIN_VALUE;
        int y_max = Integer.MIN_VALUE;
        int mapZoomMax = tileController.getTileSource().getMaxZoom();
        for (MapMarker marker : mapMarkerList) {
            int x = OsmMercator.LonToX(marker.getLon(), mapZoomMax);
            int y = OsmMercator.LatToY(marker.getLat(), mapZoomMax);
            x_max = Math.max(x_max, x);
            y_max = Math.max(y_max, y);
            x_min = Math.min(x_min, x);
            y_min = Math.min(y_min, y);
        }
        int height = Math.max(0, getHeight());
        int width = Math.max(0, getWidth());
        // System.out.println(x_min + " < x < " + x_max);
        // System.out.println(y_min + " < y < " + y_max);
        // System.out.println("tiles: " + width + " " + height);
        int newZoom = mapZoomMax;
        int x = x_max - x_min;
        int y = y_max - y_min;
        while (x > width || y > height) {
            // System.out.println("zoom: " + zoom + " -> " + x + " " + y);
            newZoom--;
            x >>= 1;
            y >>= 1;
        }
        x = x_min + (x_max - x_min) / 2;
        y = y_min + (y_max - y_min) / 2;
        int z = 1 << (mapZoomMax - newZoom);
        x /= z;
        y /= z;
        setDisplayPosition(x, y, newZoom);
    }

    /**
     * Sets the displayed map pane and zoom level so that all map markers are
     * visible.
     */
    public void setDisplayToFitMapRectangle() {
        if (mapRectangleList == null || mapRectangleList.size() == 0)
            return;
        int x_min = Integer.MAX_VALUE;
        int y_min = Integer.MAX_VALUE;
        int x_max = Integer.MIN_VALUE;
        int y_max = Integer.MIN_VALUE;
        int mapZoomMax = tileController.getTileSource().getMaxZoom();
        for (MapRectangle rectangle : mapRectangleList) {
            x_max = Math.max(x_max, OsmMercator.LonToX(rectangle.getBottomRight().getLon(), mapZoomMax));
            y_max = Math.max(y_max, OsmMercator.LatToY(rectangle.getTopLeft().getLat(), mapZoomMax));
            x_min = Math.min(x_min, OsmMercator.LonToX(rectangle.getTopLeft().getLon(), mapZoomMax));
            y_min = Math.min(y_min, OsmMercator.LatToY(rectangle.getBottomRight().getLat(), mapZoomMax));
        }
        int height = Math.max(0, getHeight());
        int width = Math.max(0, getWidth());
        // System.out.println(x_min + " < x < " + x_max);
        // System.out.println(y_min + " < y < " + y_max);
        // System.out.println("tiles: " + width + " " + height);
        int newZoom = mapZoomMax;
        int x = x_max - x_min;
        int y = y_max - y_min;
        while (x > width || y > height) {
            // System.out.println("zoom: " + zoom + " -> " + x + " " + y);
            newZoom--;
            x >>= 1;
            y >>= 1;
        }
        x = x_min + (x_max - x_min) / 2;
        y = y_min + (y_max - y_min) / 2;
        int z = 1 << (mapZoomMax - newZoom);
        x /= z;
        y /= z;
        setDisplayPosition(x, y, newZoom);
    }

    /**
     * Calculates the latitude/longitude coordinate of the center of the
     * currently displayed map area.
     * 
     * @return latitude / longitude
     */
    public Coordinate getPosition() {
        double lon = OsmMercator.XToLon(center.x, zoom);
        double lat = OsmMercator.YToLat(center.y, zoom);
        return new Coordinate(lat, lon);
    }

    /**
     * Converts the relative pixel coordinate (regarding the top left corner of
     * the displayed map) into a latitude / longitude coordinate
     * 
     * @param mapPoint
     *            relative pixel coordinate regarding the top left corner of the
     *            displayed map
     * @return latitude / longitude
     */
    public Coordinate getPosition(Point mapPoint) {
        return getPosition(mapPoint.x, mapPoint.y);
    }

    /**
     * Converts the relative pixel coordinate (regarding the top left corner of
     * the displayed map) into a latitude / longitude coordinate
     * 
     * @param mapPointX
     * @param mapPointY
     * @return
     */
    public Coordinate getPosition(int mapPointX, int mapPointY) {
        int x = center.x + mapPointX - getWidth() / 2;
        int y = center.y + mapPointY - getHeight() / 2;
        double lon = OsmMercator.XToLon(x, zoom);
        double lat = OsmMercator.YToLat(y, zoom);
        return new Coordinate(lat, lon);
    }

    /**
     * Calculates the position on the map of a given coordinate
     * 
     * @param lat
     * @param lon
     * @param checkOutside
     * @return point on the map or <code>null</code> if the point is not visible
     *         and checkOutside set to <code>true</code>
     */
    public Point getMapPosition(double lat, double lon, boolean checkOutside) {
        int x = OsmMercator.LonToX(lon, zoom);
        int y = OsmMercator.LatToY(lat, zoom);
        x -= center.x - getWidth() / 2;
        y -= center.y - getHeight() / 2;
        if (checkOutside) {
            if (x < 0 || y < 0 || x > getWidth() || y > getHeight())
                return null;
        }
        return new Point(x, y);
    }

    /**
     * Calculates the position on the map of a given coordinate
     * 
     * @param lat
     * @param lon
     * @return point on the map or <code>null</code> if the point is not visible
     */
    public Point getMapPosition(double lat, double lon) {
        return getMapPosition(lat, lon, true);
    }

    /**
     * Calculates the position on the map of a given coordinate
     * 
     * @param coord
     * @return point on the map or <code>null</code> if the point is not visible
     */
    public Point getMapPosition(Coordinate coord) {
        if (coord != null)
            return getMapPosition(coord.getLat(), coord.getLon());
        else
            return null;
    }

    /**
     * Calculates the position on the map of a given coordinate
     * 
     * @param coord
     * @return point on the map or <code>null</code> if the point is not visible
     *         and checkOutside set to <code>true</code>
     */
    public Point getMapPosition(Coordinate coord, boolean checkOutside) {
        if (coord != null)
            return getMapPosition(coord.getLat(), coord.getLon(), checkOutside);
        else
            return null;
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);

        int iMove = 0;

        int tilesize = tileSource.getTileSize();
        int tilex = center.x / tilesize;
        int tiley = center.y / tilesize;
        int off_x = (center.x % tilesize);
        int off_y = (center.y % tilesize);

        int w2 = getWidth() / 2;
        int h2 = getHeight() / 2;
        int posx = w2 - off_x;
        int posy = h2 - off_y;

        int diff_left = off_x;
        int diff_right = tilesize - off_x;
        int diff_top = off_y;
        int diff_bottom = tilesize - off_y;

        boolean start_left = diff_left < diff_right;
        boolean start_top = diff_top < diff_bottom;

        if (start_top) {
            if (start_left) {
                iMove = 2;
            } else {
                iMove = 3;
            }
        } else {
            if (start_left) {
                iMove = 1;
            } else {
                iMove = 0;
            }
        } // calculate the visibility borders
        int x_min = -tilesize;
        int y_min = -tilesize;
        int x_max = getWidth();
        int y_max = getHeight();

        // paint the tiles in a spiral, starting from center of the map
        boolean painted = true;
        int x = 0;
        while (painted) {
            painted = false;
            for (int i = 0; i < 4; i++) {
                if (i % 2 == 0) {
                    x++;
                }
                for (int j = 0; j < x; j++) {
                    if (x_min <= posx && posx <= x_max && y_min <= posy && posy <= y_max) {
                        // tile is visible
                        Tile tile = tileController.getTile(tilex, tiley, zoom);
                        if (tile != null) {
                            painted = true;
                            tile.paint(g, posx, posy);
                            if (tileGridVisible) {
                                g.drawRect(posx, posy, tilesize, tilesize);
                            }
                        }
                    }
                    Point p = move[iMove];
                    posx += p.x * tilesize;
                    posy += p.y * tilesize;
                    tilex += p.x;
                    tiley += p.y;
                }
                iMove = (iMove + 1) % move.length;
            }
        }
        // outer border of the map
        int mapSize = tilesize << zoom;
        g.drawRect(w2 - center.x, h2 - center.y, mapSize, mapSize);

        // g.drawString("Tiles in cache: " + tileCache.getTileCount(), 50, 20);

        if (mapRectanglesVisible && mapRectangleList != null) {
            for (MapRectangle rectangle : mapRectangleList) {
                Coordinate topLeft = rectangle.getTopLeft();
                Coordinate bottomRight = rectangle.getBottomRight();
                if (topLeft != null && bottomRight != null) {
                    Point pTopLeft = getMapPosition(topLeft.getLat(), topLeft.getLon(), false);
                    Point pBottomRight = getMapPosition(bottomRight.getLat(), bottomRight.getLon(), false);
                    if (pTopLeft != null && pBottomRight != null) {
                        rectangle.paint(g, pTopLeft, pBottomRight);
                    }
                }
            }
        }

        if (mapMarkersVisible && mapMarkerList != null) {
            for (MapMarker marker : mapMarkerList) {
                paintMarker(g, marker);
            }
        }
        paintAttribution(g);
    }

    /**
     * Paint a single marker.
     */
    protected void paintMarker(Graphics g, MapMarker marker) {
        Point p = getMapPosition(marker.getLat(), marker.getLon());
        if (p != null) {
            marker.paint(g, p);
        }
    }

    /**
     * Moves the visible map pane.
     * 
     * @param x
     *            horizontal movement in pixel.
     * @param y
     *            vertical movement in pixel
     */
    public void moveMap(int x, int y) {
        center.x += x;
        center.y += y;
        repaint();
    }

    /**
     * @return the current zoom level
     */
    public int getZoom() {
        return zoom;
    }

    /**
     * Increases the current zoom level by one
     */
    public void zoomIn() {
        setZoom(zoom + 1);
    }

    /**
     * Increases the current zoom level by one
     */
    public void zoomIn(Point mapPoint) {
        setZoom(zoom + 1, mapPoint);
    }

    /**
     * Decreases the current zoom level by one
     */
    public void zoomOut() {
        setZoom(zoom - 1);
    }

    /**
     * Decreases the current zoom level by one
     */
    public void zoomOut(Point mapPoint) {
        setZoom(zoom - 1, mapPoint);
    }

    public void setZoom(int zoom, Point mapPoint) {
        if (zoom > tileController.getTileSource().getMaxZoom() || zoom < tileController.getTileSource().getMinZoom()
                || zoom == this.zoom)
            return;
        Coordinate zoomPos = getPosition(mapPoint);
        tileController.cancelOutstandingJobs(); // Clearing outstanding load
        // requests
        setDisplayPositionByLatLon(mapPoint, zoomPos.getLat(), zoomPos.getLon(), zoom);
    }

    public void setZoom(int zoom) {
        setZoom(zoom, new Point(getWidth() / 2, getHeight() / 2));
    }

    /**
     * Every time the zoom level changes this method is called. Override it in
     * derived implementations for adapting zoom dependent values. The new zoom
     * level can be obtained via {@link #getZoom()}.
     * 
     * @param oldZoom
     *            the previous zoom level
     */
    protected void zoomChanged(int oldZoom) {
        zoomSlider.setToolTipText("Zoom level " + zoom);
        zoomInButton.setToolTipText("Zoom to level " + (zoom + 1));
        zoomOutButton.setToolTipText("Zoom to level " + (zoom - 1));
        zoomOutButton.setEnabled(zoom > tileController.getTileSource().getMinZoom());
        zoomInButton.setEnabled(zoom < tileController.getTileSource().getMaxZoom());
    }

    public boolean isTileGridVisible() {
        return tileGridVisible;
    }

    public void setTileGridVisible(boolean tileGridVisible) {
        this.tileGridVisible = tileGridVisible;
        repaint();
    }

    public boolean getMapMarkersVisible() {
        return mapMarkersVisible;
    }

    /**
     * Enables or disables painting of the {@link MapMarker}
     * 
     * @param mapMarkersVisible
     * @see #addMapMarker(MapMarker)
     * @see #getMapMarkerList()
     */
    public void setMapMarkerVisible(boolean mapMarkersVisible) {
        this.mapMarkersVisible = mapMarkersVisible;
        repaint();
    }

    public void setMapMarkerList(List<MapMarker> mapMarkerList) {
        this.mapMarkerList = mapMarkerList;
        repaint();
    }

    public List<MapMarker> getMapMarkerList() {
        return mapMarkerList;
    }

    public void setMapRectangleList(List<MapRectangle> mapRectangleList) {
        this.mapRectangleList = mapRectangleList;
        repaint();
    }

    public List<MapRectangle> getMapRectangleList() {
        return mapRectangleList;
    }

    public void addMapMarker(MapMarker marker) {
        mapMarkerList.add(marker);
        repaint();
    }

    public void removeMapMarker(MapMarker marker) {
        mapMarkerList.remove(marker);
        repaint();
    }

    public void addMapRectangle(MapRectangle rectangle) {
        mapRectangleList.add(rectangle);
        repaint();
    }

    public void removeMapRectangle(MapRectangle rectangle) {
        mapRectangleList.remove(rectangle);
        repaint();
    }

    public void setZoomContolsVisible(boolean visible) {
        zoomSlider.setVisible(visible);
        zoomInButton.setVisible(visible);
        zoomOutButton.setVisible(visible);
    }

    public boolean getZoomContolsVisible() {
        return zoomSlider.isVisible();
    }

    public void setTileSource(TileSource tileSource) {
        if (tileSource.getMaxZoom() > MAX_ZOOM)
            throw new RuntimeException("Maximum zoom level too high");
        if (tileSource.getMinZoom() < MIN_ZOOM)
            throw new RuntimeException("Minumim zoom level too low");
        this.tileSource = tileSource;
        tileController.setTileSource(tileSource);
        zoomSlider.setMinimum(tileSource.getMinZoom());
        zoomSlider.setMaximum(tileSource.getMaxZoom());
        tileController.cancelOutstandingJobs();
        if (zoom > tileSource.getMaxZoom()) {
            setZoom(tileSource.getMaxZoom());
        }
        boolean requireAttr = tileSource.requiresAttribution();
        if (requireAttr) {
            attrImage = tileSource.getAttributionImage();
            attrTermsUrl = tileSource.getTermsOfUseURL();
        } else {
            attrImage = null;
            attrTermsUrl = null;
        }
        repaint();
    }

    public void tileLoadingFinished(Tile tile, boolean success) {
        repaint();
    }

    public boolean isMapRectanglesVisible() {
        return mapRectanglesVisible;
    }

    /**
     * Enables or disables painting of the {@link MapRectangle}
     * 
     * @param mapMarkersVisible
     * @see #addMapRectangle(MapRectangle)
     * @see #getMapRectangleList()
     */
    public void setMapRectanglesVisible(boolean mapRectanglesVisible) {
        this.mapRectanglesVisible = mapRectanglesVisible;
        repaint();
    }

    /*
     * (non-Javadoc)
     * 
     * @see
     * org.openstreetmap.gui.jmapviewer.interfaces.TileLoaderListener#getTileCache
     * ()
     */
    public TileCache getTileCache() {
        return tileController.getTileCache();
    }

    public void setTileLoader(TileLoader loader) {
        tileController.setTileLoader(loader);
    }

    private void paintAttribution(Graphics g) {
        if (!tileSource.requiresAttribution())
            return;
        // Draw attribution
        Font font = g.getFont();
        g.setFont(ATTR_LINK_FONT);

        Rectangle2D termsStringBounds = g.getFontMetrics().getStringBounds("Background Terms of Use", g);
        int textHeight = (int) termsStringBounds.getHeight() - 5;
        int termsTextY = getHeight() - textHeight;
        if (attrTermsUrl != null) {
            int x = 2;
            int y = getHeight() - textHeight;
            g.setColor(Color.black);
            g.drawString("Background Terms of Use", x + 1, y + 1);
            g.setColor(Color.white);
            g.drawString("Background Terms of Use", x, y);
        }

        // Draw attribution logo
        if (attrImage != null) {
            int x = 2;
            int height = attrImage.getHeight(null);
            int y = termsTextY - height - textHeight - 5;
            g.drawImage(attrImage, x, y, null);
        }

        g.setFont(ATTR_FONT);
        Coordinate topLeft = getPosition(0, 0);
        Coordinate bottomRight = getPosition(getWidth(), getHeight());
        String attributionText = tileSource.getAttributionText(zoom, topLeft, bottomRight);
        if (attributionText != null) {
            Rectangle2D stringBounds = g.getFontMetrics().getStringBounds(attributionText, g);
            int x = getWidth() - (int) stringBounds.getWidth();
            int y = getHeight() - textHeight;
            g.setColor(Color.black);
            g.drawString(attributionText, x + 1, y + 1);
            g.setColor(Color.white);
            g.drawString(attributionText, x, y);
        }

        g.setFont(font);
    }
}