com.google.gwt.gadgets.client.ui.GadgetImage.java Source code

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Here is the source code for com.google.gwt.gadgets.client.ui.GadgetImage.java

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/*
 * Copyright 2008 Google Inc.
 *
 * 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 com.google.gwt.gadgets.client.ui;

import com.google.gwt.user.client.ui.Image;

/**
 * Image that will be cached by the Gadget Container unless this is not
 * executed in a Gadget Container.
 *
 * <p>The image URL appearing on the browser will not be the one set here but
 * the URL of the cached image on the Gadget container's server.
 */

public class GadgetImage extends Image {

    /**
     * Returns a proxy URL that can be used to access the given image's URL. If
     * we are not in a Gadget container, we just return the entered url
     */
    private static native String getCachedImageUrl(String url) /*-{
                                                               if($wnd.gadgets.io.getProxyUrl){
                                                               return $wnd.gadgets.io.getProxyUrl(url);
                                                               } else {
                                                               return url;
                                                               }
                                                               }-*/;

    /**
     * Constructs a new GadgetImage. This image will be cached on the container.
     */
    public GadgetImage() {
    }

    /**
     * Constructs a new GadgetImage given the image's URL. This image will be
     * cached by the Gadget container.
     *
     * @param url The URL of the image that will be cached
     */
    public GadgetImage(String url) {
        super(getCachedImageUrl(url));
    }

    /**
     * Creates a clipped image with a specified URL and visibility rectangle. The
     * visibility rectangle is declared relative to the the rectangle which
     * encompasses the entire image, which has an upper-left vertex of (0,0). The
     * load event will be fired immediately after the object has been constructed
     * (i.e. potentially before the image has been loaded in the browser). Since
     * the width and height are specified explicitly by the user, this behavior
     * will not cause problems with retrieving the width and height of a clipped
     * image in a load event handler. This image will be cached by the
     * Gadget container server.
     *
     * @param url the URL of the image to be displayed and that will be cached
     * @param left the horizontal co-ordinate of the upper-left vertex of the
     *          visibility rectangle
     * @param top the vertical co-ordinate of the upper-left vertex of the
     *          visibility rectangle
     * @param width the width of the visibility rectangle
     * @param height the height of the visibility rectangle
     */
    public GadgetImage(String url, int left, int top, int width, int height) {
        super(getCachedImageUrl(url), left, top, width, height);
    }

    /**
     * Sets the image's URL. The image will be cached first by the Gadget
     * container.
     *
     * @param url The URL of the image
     */
    @Override
    public void setUrl(String url) {
        super.setUrl(getCachedImageUrl(url));
    }

    /**
     * Sets the url and the visibility rectangle for the image at the same time.
     * A single load event will be fired if either the incoming url or visiblity
     * rectangle co-ordinates differ from the image's current url or current
     * visibility rectangle co-ordinates. If the image is currently in the
     * unclipped state, a call to this method will cause a transition to the
     * clipped state. The image will be cached first by the Gadget container.
     *
     * @param url the image URL
     * @param left the horizontal coordinate of the upper-left vertex of the
     *          visibility rectangle
     * @param top the vertical coordinate of the upper-left vertex of the
     *          visibility rectangle
     * @param width the width of the visibility rectangle
     * @param height the height of the visibility rectangle
     */
    @Override
    public void setUrlAndVisibleRect(String url, int left, int top, int width, int height) {
        super.setUrlAndVisibleRect(getCachedImageUrl(url), left, top, width, height);
    }
}