Image.java

/*
 * Copyright 2008-2009 Oliver Zoran
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.iplantc.phyloviewer.client.tree.viewer.canvas;

import com.google.gwt.dom.client.ImageElement;

/**
 * Canvas image which may be used by the <code>Canvas.drawImage(...)</code>
 * methods.
 */
public class Image {

	/**
	 * An optional loading listener callback method.
	 */
	private ImageListener loadingListener;

	/**
	 * The actual image element.
	 */
	private ImageElement imageElement;

	/**
	 * Flag that indicates the loading status.
	 */
	private boolean loaded;

	/**
	 * Creates an image object that will not give any notifications on its own
	 * when it's actual data has been loaded by the browser.
	 * 
	 * @param url to an image file (GIF, JPEG, PNG)
	 */
	public Image(String url) {
		this(url, null);
	}

	/**
	 * Creates an image object that will notify the given callback listener
	 * when it's actual data has been loaded by the browser.
	 * 
	 * @param url to an image file (GIF, JPEG, PNG)
	 * @param listener a user defined callback method
	 */
	public Image(String url, ImageListener listener) {
		if (url == null) {
			throw new IllegalArgumentException();
		}
		loadingListener = listener;
		imageElement = getNativeHandle();
		imageElement.setSrc(url);
	}

	/**
	 * Creates an image handle that will notify the {@link Image} instance, if
	 * it has loaded it's actual data successfully.
	 * 
	 * @return an ImageElement object
	 */
	private native ImageElement getNativeHandle() /*-{
		var self = this;
		var image = new Image();
		image.onload = function() {
			self.@org.iplantc.phyloviewer.client.tree.viewer.canvas.Image::invokeCallback()();
			image.onload = null;
		}
		return image;
	}-*/;

	/**
	 * Invokes the {@link Image.ImageListener} instance, if any.
	 */
	@SuppressWarnings("unused")
	private void invokeCallback() {
		loaded = true;
		if (loadingListener != null) {
			loadingListener.onLoadingComplete(this);
			loadingListener = null;
		}
	}

	/**
	 * Use this method to determine if the actual image has already been
	 * loaded by the browser.
	 * 
	 * @return true when loaded, false otherwise
	 */
	public boolean isLoaded() {
		return loaded;
	}

	/**
	 * Returns the actual image DOM element.
	 * 
	 * @return the image element
	 */
	public ImageElement getElement() {
		return imageElement;
	}

	/**
	 * Returns the image's width or -1 if it has not yet been loaded
	 * 
	 * @return the width or -1 if unknown
	 */
	public int getWidth() {
		if (imageElement != null) {
			return imageElement.getWidth();
		}
		return -1;
	}

	/**
	 * Returns the image's height or -1 if it has not yet been loaded
	 * 
	 * @return the height or -1 if unknown
	 */
	public int getHeight() {
		if (imageElement != null) {
			return imageElement.getHeight();
		}
		return -1;
	}
}