import java.awt.*;
import java.net.*; 

/** A class for displaying images. It places the Image
 *  into a canvas so that it can moved around by layout
 *  managers, will get repainted automatically, etc.
 *  No mouseXXX or action events are defined, so it is
 *  most similar to the Label Component.
 *  <P>
 *  By default, with FlowLayout the ImageLabel takes
 *  its minimum size (just enclosing the image). The
 *  default with BorderLayout is to expand to fill
 *  the region in width (North/South), height
 *  (East/West) or both (Center). This is the same
 *  behavior as with the builtin Label class. If you
 *  give an explicit setSize or
 *  setBounds call <B>before</B> adding the
 *  ImageLabel to the Container, this size will
 *  override the defaults.
 *  <P>
 *  Here is an example of its use:
 *  <P>
 *  <PRE>
 *  public class ShowImages extends Applet {
 *    private ImageLabel image1, image2;
 *
 *    public void init() {
 *      image1 = new ImageLabel(getCodeBase(),
 *                              "some-image.gif");
 *      image2 = new ImageLabel(getCodeBase(),
 *                              "other-image.jpg");
 *      add(image1);
 *      add(image2);
 *    }
 *  }
 *  </PRE>
 *
 *  Taken from Core Web Programming from 
 *  Prentice Hall and Sun Microsystems Press,
 *  http://www.corewebprogramming.com/.
 *  &copy; 2001 Marty Hall and Larry Brown;
 *  may be freely used or adapted. 
 */

public class ImageLabel extends Canvas {
  // Instance variables.
  
  // The actual Image drawn on the canvas. 
  private Image image;

  // A String corresponding to the URL of the image you will 
  // get if you call the constructor with no arguments.
  private static String defaultImageString
    = "http://java.sun.com/lib/images/" +
      "logo.java.color-transp.55x60.gif";

  // The URL of the image. But sometimes we will use an existing
  // image object (e.g. made by createImage) for which this info 
  // will not be available, so a default string is used here.
  private String imageString = "<Existing Image>";

  // Turn this on to get verbose debugging messages. 
  private boolean debug = false;

  /** Amount of extra space around the image. */
  
  private int border = 0;

  /** If there is a non-zero border, what color should it be? 
   *  Default is to use the background color of the Container.
   */
   
  private Color borderColor = null;
  
  // Width and height of the Canvas. This is the
  //  width/height of the image plus twice the border.
  private int width, height;

  /** Determines if it will be sized automatically. If the user
   *  issues a setSize() or setBounds()call before adding the 
   *  label to the Container, or if the LayoutManager resizes 
   *  before drawing (as with BorderLayout), then those sizes
   *  override the default, which is to make the label the same 
   *  size as the image it holds (after reserving space for the 
   *  border, if any). This flag notes this, so subclasses that
   *  override ImageLabel need to check this flag, and if it is 
   *  true, and they draw modified image, then they need to draw 
   *  them based on the width height variables, not just blindly 
   *  drawing them full size.
   */
   
  private boolean explicitSize = false;
  private int explicitWidth=0, explicitHeight=0;
  
  // The MediaTracker that can tell if image has been loaded 
  // before trying to paint it or setSize based on its size.
  private MediaTracker tracker;
  
  // Used by MediaTracker to be sure image is loaded before 
  // paint & setSize, since you can't find out the size until it
  // is done loading.
  private static int lastTrackerID=0;
  private int currentTrackerID;
  private boolean doneLoading = false;

  private Container parentContainer;

  /** Create an ImageLabel with the default image.
   *
   * @see #getDefaultImageString
   * @see #setDefaultImageString
   */
  // Remember that the funny "this()" syntax calls
  // constructor of same class
  public ImageLabel() {
    this(defaultImageString);
  }
  
  /** Create an ImageLabel using the image at URL
   *  specified by the string.
   *
   * @param imageURLString A String specifying the
   *   URL of the image.
   */
   
  public ImageLabel(String imageURLString) {
    this(makeURL(imageURLString));
  }

  /** Create an ImageLabel using the image at URL
   *  specified.
   *
   * @param imageURL The URL of the image.
   */
   
  public ImageLabel(URL imageURL) {
    this(loadImage(imageURL));
    imageString = imageURL.toExternalForm();
  }

  /** Create an ImageLabel using the image in the file
   *  in the specified directory.
   *
   * @param imageDirectory Directory containing image
   * @param file Filename of image
   */
   
  public ImageLabel(URL imageDirectory, String file) {
    this(makeURL(imageDirectory, file));
    imageString = file;
  }
  
  /** Create an ImageLabel using the image specified. The other
   *  constructors eventually call this one, but you may want 
   *  to call it directly if you already have an image (e.g. 
   *  created through createImage).
   *
   * @param image The image
   */
   
  public ImageLabel(Image image) {
    this.image = image;
    tracker = new MediaTracker(this);
    currentTrackerID = lastTrackerID++;
    tracker.addImage(image, currentTrackerID);
  }

  /** Makes sure that the Image associated with the Canvas is 
   *  done loading before returning, since loadImage spins off
   *  a separate thread to do the loading. Once you get around 
   *  to drawing the image, this will make sure it is loaded,
   *  waiting if not. The user does not need to call this at 
   *  all, but if several ImageLabels are used in the same 
   *  Container, this can cause several repeated layouts, so 
   *  users might want to explicitly call this themselves before
   *  adding the ImageLabel to the Container. Another 
   *  alternative is to start asynchronous loading by calling 
   *  prepareImage on the ImageLabel's image (see getImage). 
   *
   * @param doLayout Determines if the Container should be 
   *   re-laid out after you are finished waiting. <B>This 
   *   should be true when called from user functions</B>, 
   *   but is set to false when called from getPreferredSize 
   *   to avoid an infinite loop. This is needed when using 
   *   BorderLayout, which calls getPreferredSize
   *   <B>before</B> calling paint.
   */
   
  public void waitForImage(boolean doLayout) {
    if (!doneLoading) {
      debug("[waitForImage] - Resizing and waiting for "
            + imageString);
      try { tracker.waitForID(currentTrackerID); } 
      catch (InterruptedException ie) {} 
      catch (Exception e) { 
        System.out.println("Error loading "
                           + imageString + ": "
                           + e.getMessage()); 
        e.printStackTrace(); 
      } 
      if (tracker.isErrorID(0)) 
        new Throwable("Error loading image "
                      + imageString).printStackTrace();
      doneLoading = true;
      if (explicitWidth != 0)
        width = explicitWidth;
      else
        width = image.getWidth(this) + 2*border;
      if (explicitHeight != 0)
        height = explicitHeight;
      else
        height = image.getHeight(this) + 2*border;
      setSize(width, height);
      debug("[waitForImage] - " + imageString + " is "
            + width + "x" + height + ".");

      // If no parent, you are OK, since it will have
      // been resized before being added. But if
      // parent exists, you have already been added,
      // and the change in size requires re-layout. 
      if (((parentContainer = getParent()) != null)
          && doLayout) {
        setBackground(parentContainer.getBackground());
        parentContainer.doLayout();
      }
    }
  }

  /** Moves the image so that it is <I>centered</I> at
   *  the specified location, as opposed to the setLocation
   *  method of Component which places the top left
   *  corner at the specified location.
   *  <P>
   *  <B>Note:</B> The effects of this could be undone
   *  by the LayoutManager of the parent Container, if
   *  it is using one. So this is normally only used
   *  in conjunction with a null LayoutManager.
   *
   * @param x The X coord of center of the image
   *          (in parent's coordinate system)
   * @param y The Y coord of center of the image
   *          (in parent's coordinate system)
   * @see java.awt.Component#setLocation
   */

  public void centerAt(int x, int y) {
    debug("Placing center of " + imageString + " at ("
          + x + "," + y + ")");
    setLocation(x - width/2, y - height/2); 
  }

  /** Determines if the x and y <B>(in the ImageLabel's
   *  own coordinate system)</B> is inside the
   *  ImageLabel. Put here because Netscape 2.02 has
   *  a bug in which it doesn't process contains() and
   *  locate() tests correctly. 
   */
   
  public synchronized boolean contains(int x, int y) {
    return((x >= 0) && (x <= width)
           && (y >= 0) && (y <= height));
  }
  
  /** Draws the image. If you override this in a
   *  subclass, be sure to call super.paint.
   */
   
  public void paint(Graphics g) {
    if (!doneLoading)
      waitForImage(true);
    else {
      if (explicitSize)
        g.drawImage(image, border, border,
                    width-2*border, height-2*border,
                    this);
      else
        g.drawImage(image, border, border, this);
      drawRect(g, 0, 0, width-1, height-1,
               border, borderColor);
    }
  }

  /** Used by layout managers to calculate the usual
   *  size allocated for the Component. Since some
   *  layout managers (e.g. BorderLayout) may
   *  call this before paint is called, you need to
   *  make sure that the image is done loading, which
   *  will force a setSize, which determines the values
   *  returned.
   */
  public Dimension getPreferredSize() {
    if (!doneLoading)
      waitForImage(false);
    return(super.getPreferredSize());
  }

  /** Used by layout managers to calculate the smallest
   *  size allocated for the Component. Since some
   *  layout managers (e.g. BorderLayout) may
   *  call this before paint is called, you need to
   *  make sure that the image is done loading, which
   *  will force a setSize, which determines the values
   *  returned.
   */
   public Dimension getMinimumSize() {
     if (!doneLoading)
       waitForImage(false);
     return(super.getMinimumSize());
   }
  
  // LayoutManagers (such as BorderLayout) might call
  // setSize or setBounds with only 1 dimension of
  // width/height non-zero. In such a case, you still
  // want the other dimension to come from the image
  // itself.

  /** Resizes the ImageLabel. If you don't setSize the
   *  label explicitly, then what happens depends on
   *  the layout manager. With FlowLayout, as with
   *  FlowLayout for Labels, the ImageLabel takes its
   *  minimum size, just enclosing the image. With
   *  BorderLayout, as with BorderLayout for Labels,
   *  the ImageLabel is expanded to fill the
   *  section. Stretching GIF/JPG files does not always
   *  result in clear looking images. <B>So just as
   *  with builtin Labels and Buttons, don't
   *  use FlowLayout if you don't want the Buttons to
   *  get resized.</B> If you don't use any
   *  LayoutManager, then the ImageLabel will also
   *  just fit the image.
   *  <P>
   *  Note that if you setSize explicitly, you must do
   *  it <B>before</B> the ImageLabel is added to the
   *  Container. In such a case, the explicit size
   *  overrides the image dimensions.
   *
   * @see #setBounds
   */
   
  public void setSize(int width, int height) {
    if (!doneLoading) {
      explicitSize=true;
      if (width > 0)
        explicitWidth=width;
      if (height > 0)
        explicitHeight=height;
    }
    super.setSize(width, height);
  }

  /** Resizes the ImageLabel. If you don't setSize the
   *  label explicitly, then what happens depends on
   *  the layout manager. With FlowLayout, as with
   *  FlowLayout for Labels, the ImageLabel takes its
   *  minimum size, just enclosing the image. With
   *  BorderLayout, as with BorderLayout for Labels,
   *  the ImageLabel is expanded to fill the
   *  section. Stretching GIF/JPG files does not always
   *  result in clear looking images. <B>So just as
   *  with builtin Labels and Buttons, don't
   *  use FlowLayout if you don't want the Buttons to
   *  get resized.</B> If you don't use any
   *  LayoutManager, then the ImageLabel will also
   *  just fit the image.
   *  <P>
   *  Note that if you setSize explicitly, you must do
   *  it <B>before</B> the ImageLabel is added to the
   *  Container. In such a case, the explicit size
   *  overrides the image dimensions.
   *
   * @see #setSize
   */
   
  public void setBounds(int x, int y,
                      int width, int height) {
    if (!doneLoading) {
      explicitSize=true;
      if (width > 0)
        explicitWidth=width;
      if (height > 0)
        explicitHeight=height;
    }
    super.setBounds(x, y, width, height);
  }
  
  // You can't just set the background color to
  // the borderColor and skip drawing the border,
  // since it messes up transparent gifs. You
  // need the background color to be the same as
  // the container.
  
  /** Draws a rectangle with the specified OUTSIDE
   *  left, top, width, and height.
   *  Used to draw the border.
   */
   
  protected void drawRect(Graphics g,
                          int left, int top,
                          int width, int height,
                          int lineThickness,
                          Color rectangleColor) {
    g.setColor(rectangleColor);
    for(int i=0; i<lineThickness; i++) {
      g.drawRect(left, top, width, height);
      if (i < lineThickness-1) {  // Skip last iteration
        left = left + 1;
        top = top + 1;
        width = width - 2;
        height = height - 2;
      }
    }
  }
  
  /** Calls System.out.println if the debug variable
   *  is true; does nothing otherwise.
   *
   * @param message The String to be printed.
   */
   
  protected void debug(String message) {
    if (debug)
      System.out.println(message);
  }
  
  // Creates the URL with some error checking.
  
  private static URL makeURL(String s) {
    URL u = null;
    try { u = new URL(s); }
    catch (MalformedURLException mue) {
      System.out.println("Bad URL " + s + ": " + mue);
      mue.printStackTrace();
    }
    return(u);
  }

  private static URL makeURL(URL directory,
                             String file) {
    URL u = null;
    try { u = new URL(directory, file); }
    catch (MalformedURLException mue) {
      System.out.println("Bad URL " +
                         directory.toExternalForm() +
                         ", " + file + ": " + mue);
      mue.printStackTrace();
    }
    return(u);
  }

  // Loads the image. Needs to be static since it is
  // called by the constructor.
  
  private static Image loadImage(URL url) {
    return(Toolkit.getDefaultToolkit().getImage(url));
  }

  /** The Image associated with the ImageLabel. */

  public Image getImage() {
    return(image);
  }
  
  /** Gets the border width. */

  public int getBorder() {
    return(border);
  }

  /** Sets the border thickness. */
  
  public void setBorder(int border) {
    this.border = border;
  }

  /** Gets the border color. */

  public Color getBorderColor() {
    return(borderColor);
  }

  /** Sets the border color. */
  
  public void setBorderColor(Color borderColor) {
    this.borderColor = borderColor;
  }
  
  // You could just call size().width and size().height,
  // but since we've overridden setSize to record
  // this, we might as well use it.
  
  /** Gets the width (image width plus twice border). */

  public int getWidth() {
    return(width);
  }

  /** Gets the height (image height plus 2x border). */

  public int getHeight() {
    return(height);
  }
  
  /** Has the ImageLabel been given an explicit size?
   *  This is used to decide if the image should be
   *  stretched or not. This will be true if you
   *  call setSize or setBounds on the ImageLabel before
   *  adding it to a Container. It will be false
   *  otherwise.
   */
   
  protected boolean hasExplicitSize() {
    return(explicitSize);
  }

  /** Returns the string representing the URL that
   *  will be used if none is supplied in the
   *  constructor.
   */
   
  public static String getDefaultImageString() {
    return(defaultImageString);
  }

  /** Sets the string representing the URL that
   *  will be used if none is supplied in the
   *  constructor. Note that this is static,
   *  so is shared by all ImageLabels. Using this
   *  might be convenient in testing, but "real"
   *  applications should avoid it.
   */
   
  public static void setDefaultImageString(String file) {
    defaultImageString = file;
  }

  /** Returns the string representing the URL
   *  of image.
   */
   
  protected String getImageString() {
    return(imageString);
  }

  /** Is the debugging flag set? */
   
  public boolean isDebugging() {
    return(debug);
  }

  /** Set the debugging flag. Verbose messages
   *  will be printed to System.out if this is true.
   */
  public void setIsDebugging(boolean debug) {
    this.debug = debug;
  }
}