89 lines
2.7 KiB
JavaScript
89 lines
2.7 KiB
JavaScript
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/*
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* Creating and deleting IMG nodes seems to cause memory leaks in WebKit, but
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* there are also reports that keeping the same node and replacing src can cause
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* memory leaks (also in WebKit).
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*
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* So we don't have to depend on doing one or the other in other code, abstract
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* this. Use ImgPool.get() and ImgPool.release() to retrieve a new IMG node and
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* return it. We can choose here to either keep a pool, to avoid constantly
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* creating new ones, or to throw them away and create new ones, to avoid changing
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* src.
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*
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* This doesn't clear styles or any other properties. To avoid leaking things from
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* one type of image to another, use separate pools for each.
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*/
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var ImgPoolHandlerWebKit = Class.create({
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initialize: function()
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{
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this.pool = [];
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this.pool_waiting = [];
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this.blank_image_loaded_event = this.blank_image_loaded_event.bind(this);
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},
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get: function()
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{
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if(this.pool.length == 0)
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{
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// debug("No images in pool; creating blank");
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return $(document.createElement("IMG"));
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}
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// debug("Returning image from pool");
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return this.pool.pop();
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},
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release: function(img)
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{
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/*
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* Replace the image with a blank, so when it's reused it doesn't show the previously-
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* loaded image until the new one is available. Don't reuse the image until the blank
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* image is loaded.
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*
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* This also encourages the browser to abort any running download, so if we have a large
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* PNG downloading that we've cancelled it won't continue and download the whole thing.
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* Note that Firefox will stop a download if we do this, but not if we only remove an
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* image from the document.
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*/
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img.observe("load", this.blank_image_loaded_event);
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this.pool_waiting.push(img);
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img.src = "/images/blank.png";
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},
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blank_image_loaded_event: function(event)
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{
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var img = event.target;
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img.stopObserving("load", this.blank_image_loaded_event);
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this.pool_waiting = this.pool_waiting.without(img);
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this.pool.push(img);
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}
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});
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var ImgPoolHandlerDummy = Class.create({
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get: function()
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{
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return $(document.createElement("IMG"));
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},
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release: function(img)
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{
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img.src = "/images/blank.png";
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}
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});
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/* Create an image pool handler. If the URL hash value "image-pools" is specified,
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* force image pools on or off for debugging; otherwise enable them only when needed. */
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var ImgPoolHandler = function()
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{
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var use_image_pools = Prototype.Browser.WebKit;
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var hash_value = UrlHash.get("image-pools");
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if(hash_value != null)
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use_image_pools = (hash_value != "0");
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if(use_image_pools)
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return new ImgPoolHandlerWebKit(arguments);
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else
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return new ImgPoolHandlerDummy(arguments);
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}
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