2.1/user/src/com/google/gwt/dom/client/ImageSrcIE6.java - gwt - Git at Google

 /*
  * Copyright 2007 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.dom.client;

 import com.google.gwt.core.client.JavaScriptObject;

 /**
  * Works around an IE problem where multiple images trying to load at the same
  * time will generate a request per image. We fix this by only allowing the
  * first image of a given URL to set its source immediately, but simultaneous
  * requests for the same URL don't actually get their source set until the
  * original load is complete.
  */
 class ImageSrcIE6 {

   /**
    * A native map of image source URL strings to Image objects. All Image
    * objects with values in this map are waiting on an asynchronous load to
    * complete and have event handlers hooked. The moment the image finishes
    * loading, it will be removed from this map.
    */
   private static JavaScriptObject srcImgMap;

   static {
     executeBackgroundImageCacheCommand();
   }

   /**
    * Returns the src of the image, or the pending src if the image is pending.
    */
   public static native String getImgSrc(Element img) /*-{
     return img.__pendingSrc || img.src;
   }-*/;

   /**
    * Sets the src of the image, queuing up with other requests for the same URL
    * if necessary. If the element is a clone, it may think it is in a pending
    * state but will not be updated properly when the image loads, so we need to
    * add it to the queue.
    */
   public static void setImgSrc(Element img, String src) {
     // We can't early out yet because the img may be a clone that needs to be
     // cleaned up and added to the list of children.
     boolean isSameSource = getImgSrc(img).equals(src);

     // Lazy init the map
     if (srcImgMap == null) {
       srcImgMap = JavaScriptObject.createObject();
     }
     // See if this element is already pending.
     String oldSrc = getPendingSrc(img);
     if (oldSrc != null) {
       // The element is pending; there must be a top node for this src.
       Element top = getTop(srcImgMap, oldSrc);
       if (top == null) {
         // This is a clone, so clean it up.
         cleanupExpandos(img);
       } else if (top.equals(img)) {
         if (isSameSource) {
           // Early out as this is the top element, and therefore not a clone.
           return;
         }

         // It's a pending parent.
         removeTop(srcImgMap, top);
       } else if (removeChild(top, img, isSameSource)) {
         // It's a pending child.
         if (isSameSource) {
           // Early out as this is a known child, and therefore not a clone.
           return;
         }
       } else {
         // The child wasn't found, so this is a clone.
         cleanupExpandos(img);
       }
     }

     // Now load the new src URL.
     Element top = getTop(srcImgMap, src);
     if (top == null) {
       // There is no existing pending parent.
       addTop(srcImgMap, img, src);
     } else {
       // There is an existing pending parent.
       addChild(top, img);
     }
   }

   /**
    * Adds an image as a child to a pending parent.
    */
   private static native void addChild(Element parent, Element child) /*-{
     parent.__kids.push(child);
     child.__pendingSrc = parent.__pendingSrc;
   }-*/;

   /**
    * Sets an image as the pending parent for the specified URL.
    */
   private static native void addTop(JavaScriptObject srcImgMap, Element img,
       String src) /*-{
     // No outstanding requests; load the image.
     img.src = src;

     // If the image was in cache, the load may have just happened synchronously.
     if (img.complete) {
       // We're done
       return;
     }

     // Image is loading asynchronously; put in map for chaining.
     img.__kids = [];
     img.__pendingSrc = src;
     srcImgMap[src] = img;

     var _onload = img.onload, _onerror = img.onerror, _onabort = img.onabort;

     // Same cleanup code matter what state we end up in.
     function finish(_originalHandler) {
       // Grab a copy of the kids.
       var kids = img.__kids;
       img.__cleanup();

       // Set the src for all kids in a timer to ensure caching has happened.
       window.setTimeout(function() {
         for (var i = 0; i < kids.length; ++i) {
           var kid = kids[i];
           if (kid.__pendingSrc == src) {
             kid.src = src;
             kid.__pendingSrc = null;
           }
         }
       }, 0);

       // Call the original handler, if any.
       _originalHandler && _originalHandler.call(img);
     }

     img.onload = function() {
       finish(_onload);
     }
     img.onerror = function() {
       finish(_onerror);
     }
     img.onabort = function() {
       finish(_onabort);
     }

     img.__cleanup = function() {
       img.onload = _onload;
       img.onerror = _onerror;
       img.onabort = _onabort;
       img.__cleanup = img.__pendingSrc = img.__kids = null;
       delete srcImgMap[src];
     }
   }-*/;

   /**
    * Cleanup an img element that was created using cloneNode.
    *
    * @param img the img element
    */
   private static native void cleanupExpandos(Element img) /*-{
     img.__cleanup = img.__pendingSrc = img.__kids = null;
   }-*/;

   private static native void executeBackgroundImageCacheCommand() /*-{
     // Fix IE background image refresh bug, present through IE6
     // see http://www.mister-pixel.com/#Content__state=is_that_simple
     // this only works with IE6 SP1+
     try {
       $doc.execCommand("BackgroundImageCache", false, true);
     } catch (e) {
       // ignore error on other browsers
     }
   }-*/;

   /**
    * Returns the pending src URL of an image, or <code>null</code> if the image
    * has no pending src URL.
    */
   private static native String getPendingSrc(Element img) /*-{
     return img.__pendingSrc;
   }-*/;

   /**
    * Returns the pending parent for the specified URL, or <code>null</code> if
    * there is no pending parent for the specified URL.
    */
   private static native Element getTop(JavaScriptObject srcImgMap, String src) /*-{
     return srcImgMap[src];
   }-*/;

   /**
    * Removes a child image from its pending parent. If checkOnly is true, the
    * method will only check that the child is a child of the parent.
    *
    * @param parent the top element that is loading the source
    * @param child the child to remove
    * @param checkOnly if true, only verify that the child is a child of parent
    * @return true if the child is found, false if not
    */
   private static native boolean removeChild(Element parent, Element child,
       boolean checkOnly) /*-{
     var kids = parent.__kids;
     for (var i = 0, c = kids.length; i < c; ++i) {
       if (kids[i] === child) {
         if (!checkOnly) {
           kids.splice(i, 1);
           child.__pendingSrc = null;
         }
         return true;
       }
     }

     // If the child isn't in any kids lists, it must be a clone.
     return false;
   }-*/;

   /**
    * Removes a pending parent's pending status, in preparation for changing its
    * URL to something else.
    */
   private static native void removeTop(JavaScriptObject srcImgMap, Element img) /*-{
     var src = img.__pendingSrc;
     var kids = img.__kids;
     img.__cleanup();

     // Restructure the kids, if any.
     if (img = kids[0]) {
       // Try to elect a new top node.
       img.__pendingSrc = null;
       @com.google.gwt.dom.client.ImageSrcIE6::addTop(Lcom/google/gwt/core/client/JavaScriptObject;Lcom/google/gwt/dom/client/Element;Ljava/lang/String;)(srcImgMap, img, src);
       if (img.__pendingSrc) {
         // It became a top node, add the rest as children.
         kids.splice(0, 1);
         img.__kids = kids;
       } else {
         // It loaded immediately; just finish the rest.
         // This is an extremely unlikely case, but could theoretically happen
         // depending on how a browser's network and UI threads are synchronized.
         for (var i = 1, c = kids.length; i < c; ++i) {
           kids[i].src = src;
           kids[i].__pendingSrc = null;
         }
       }
     }
   }-*/;
 }
	/*
	* Copyright 2007 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.dom.client;

	import com.google.gwt.core.client.JavaScriptObject;

	/**
	* Works around an IE problem where multiple images trying to load at the same
	* time will generate a request per image. We fix this by only allowing the
	* first image of a given URL to set its source immediately, but simultaneous
	* requests for the same URL don't actually get their source set until the
	* original load is complete.
	*/
	class ImageSrcIE6 {

	/**
	* A native map of image source URL strings to Image objects. All Image
	* objects with values in this map are waiting on an asynchronous load to
	* complete and have event handlers hooked. The moment the image finishes
	* loading, it will be removed from this map.
	*/
	private static JavaScriptObject srcImgMap;

	static {
	executeBackgroundImageCacheCommand();
	}

	/**
	* Returns the src of the image, or the pending src if the image is pending.
	*/
	public static native String getImgSrc(Element img) /*-{
	return img.__pendingSrc \|\| img.src;
	}-*/;

	/**
	* Sets the src of the image, queuing up with other requests for the same URL
	* if necessary. If the element is a clone, it may think it is in a pending
	* state but will not be updated properly when the image loads, so we need to
	* add it to the queue.
	*/
	public static void setImgSrc(Element img, String src) {
	// We can't early out yet because the img may be a clone that needs to be
	// cleaned up and added to the list of children.
	boolean isSameSource = getImgSrc(img).equals(src);

	// Lazy init the map
	if (srcImgMap == null) {
	srcImgMap = JavaScriptObject.createObject();
	}
	// See if this element is already pending.
	String oldSrc = getPendingSrc(img);
	if (oldSrc != null) {
	// The element is pending; there must be a top node for this src.
	Element top = getTop(srcImgMap, oldSrc);
	if (top == null) {
	// This is a clone, so clean it up.
	cleanupExpandos(img);
	} else if (top.equals(img)) {
	if (isSameSource) {
	// Early out as this is the top element, and therefore not a clone.
	return;
	}

	// It's a pending parent.
	removeTop(srcImgMap, top);
	} else if (removeChild(top, img, isSameSource)) {
	// It's a pending child.
	if (isSameSource) {
	// Early out as this is a known child, and therefore not a clone.
	return;
	}
	} else {
	// The child wasn't found, so this is a clone.
	cleanupExpandos(img);
	}
	}

	// Now load the new src URL.
	Element top = getTop(srcImgMap, src);
	if (top == null) {
	// There is no existing pending parent.
	addTop(srcImgMap, img, src);
	} else {
	// There is an existing pending parent.
	addChild(top, img);
	}
	}

	/**
	* Adds an image as a child to a pending parent.
	*/
	private static native void addChild(Element parent, Element child) /*-{
	parent.__kids.push(child);
	child.__pendingSrc = parent.__pendingSrc;
	}-*/;

	/**
	* Sets an image as the pending parent for the specified URL.
	*/
	private static native void addTop(JavaScriptObject srcImgMap, Element img,
	String src) /*-{
	// No outstanding requests; load the image.
	img.src = src;

	// If the image was in cache, the load may have just happened synchronously.
	if (img.complete) {
	// We're done
	return;
	}

	// Image is loading asynchronously; put in map for chaining.
	img.__kids = [];
	img.__pendingSrc = src;
	srcImgMap[src] = img;

	var _onload = img.onload, _onerror = img.onerror, _onabort = img.onabort;

	// Same cleanup code matter what state we end up in.
	function finish(_originalHandler) {
	// Grab a copy of the kids.
	var kids = img.__kids;
	img.__cleanup();

	// Set the src for all kids in a timer to ensure caching has happened.
	window.setTimeout(function() {
	for (var i = 0; i < kids.length; ++i) {
	var kid = kids[i];
	if (kid.__pendingSrc == src) {
	kid.src = src;
	kid.__pendingSrc = null;
	}
	}
	}, 0);

	// Call the original handler, if any.
	_originalHandler && _originalHandler.call(img);
	}

	img.onload = function() {
	finish(_onload);
	}
	img.onerror = function() {
	finish(_onerror);
	}
	img.onabort = function() {
	finish(_onabort);
	}

	img.__cleanup = function() {
	img.onload = _onload;
	img.onerror = _onerror;
	img.onabort = _onabort;
	img.__cleanup = img.__pendingSrc = img.__kids = null;
	delete srcImgMap[src];
	}
	}-*/;

	/**
	* Cleanup an img element that was created using cloneNode.
	*
	* @param img the img element
	*/
	private static native void cleanupExpandos(Element img) /*-{
	img.__cleanup = img.__pendingSrc = img.__kids = null;
	}-*/;

	private static native void executeBackgroundImageCacheCommand() /*-{
	// Fix IE background image refresh bug, present through IE6
	// see http://www.mister-pixel.com/#Content__state=is_that_simple
	// this only works with IE6 SP1+
	try {
	$doc.execCommand("BackgroundImageCache", false, true);
	} catch (e) {
	// ignore error on other browsers
	}
	}-*/;

	/**
	* Returns the pending src URL of an image, or <code>null</code> if the image
	* has no pending src URL.
	*/
	private static native String getPendingSrc(Element img) /*-{
	return img.__pendingSrc;
	}-*/;

	/**
	* Returns the pending parent for the specified URL, or <code>null</code> if
	* there is no pending parent for the specified URL.
	*/
	private static native Element getTop(JavaScriptObject srcImgMap, String src) /*-{
	return srcImgMap[src];
	}-*/;

	/**
	* Removes a child image from its pending parent. If checkOnly is true, the
	* method will only check that the child is a child of the parent.
	*
	* @param parent the top element that is loading the source
	* @param child the child to remove
	* @param checkOnly if true, only verify that the child is a child of parent
	* @return true if the child is found, false if not
	*/
	private static native boolean removeChild(Element parent, Element child,
	boolean checkOnly) /*-{
	var kids = parent.__kids;
	for (var i = 0, c = kids.length; i < c; ++i) {
	if (kids[i] === child) {
	if (!checkOnly) {
	kids.splice(i, 1);
	child.__pendingSrc = null;
	}
	return true;
	}
	}

	// If the child isn't in any kids lists, it must be a clone.
	return false;
	}-*/;

	/**
	* Removes a pending parent's pending status, in preparation for changing its
	* URL to something else.
	*/
	private static native void removeTop(JavaScriptObject srcImgMap, Element img) /*-{
	var src = img.__pendingSrc;
	var kids = img.__kids;
	img.__cleanup();

	// Restructure the kids, if any.
	if (img = kids[0]) {
	// Try to elect a new top node.
	img.__pendingSrc = null;
	@com.google.gwt.dom.client.ImageSrcIE6::addTop(Lcom/google/gwt/core/client/JavaScriptObject;Lcom/google/gwt/dom/client/Element;Ljava/lang/String;)(srcImgMap, img, src);
	if (img.__pendingSrc) {
	// It became a top node, add the rest as children.
	kids.splice(0, 1);
	img.__kids = kids;
	} else {
	// It loaded immediately; just finish the rest.
	// This is an extremely unlikely case, but could theoretically happen
	// depending on how a browser's network and UI threads are synchronized.
	for (var i = 1, c = kids.length; i < c; ++i) {
	kids[i].src = src;
	kids[i].__pendingSrc = null;
	}
	}
	}
	}-*/;
	}