52581 2011-01-17 08:10:07 -0800 preventDefault() in beforeload is not preventing image requests 2012-02-06 12:45:03 -0800 1 1 1 Unclassified WebKit DOM 528+ (Nightly build) Mac (Intel) OS X 10.6 RESOLVED WONTFIX http://www.nearinfinity.com/blogs/jeff_kunkle/lessons_learned_building_an_ht.html InRadar P2 Normal --- 1 kunklejr webkit-unassigned aestes ap aroben darin fam.lam gavinp jberlin koivisto webkit-bug-importer oldest_to_newest 335338 0 kunklejr 2011-01-17 08:10:07 -0800 Event handlers for Webkit's beforeload event can call preventDefault() to prevent a resource from being loaded into the DOM. However, it does not prevent the resource from being requested. For example, if I wanted to build a text-only version of my website, I could use the beforeload event to cancel loading of all image resources. Unfortunately, Webkit will make a network request for them anyway and just not place them in the DOM for display. This behavior defeats the usefulness of "preventing" the load since bandwidth will be used to download images that will never be shown. Another example would be an ad blocker extension. While the extension could prevent ads from being displayed, it could not speed things up by preventing them from being requested over the network. In the same vein, while the user wouldn't see the ads, they would still be tracked by the ad service since the requests are made regardless of whether preventDefault() is called. The beforeload event is great, but it would be even more valuable if calling preventDefault() on the beforeload event would cancel the request entirely. 336213 1 ap 2011-01-18 16:51:55 -0800 This sounds like a good use case to me, but starting a network load only when there's a DOM element to dispatch the beforeload event on would make resource prefetching impossible. 337794 2 gavinp 2011-01-20 18:43:55 -0800 Alexey, I'm confused: the problem Jeff's reporting is that preventDefault() in a captured beforeload doesn't work. This means extensions like the Incognito extension don't actually work as advertised, since they share cookies with the remote site and make a request with a valid Referer. Are you talking about bug 52577 instead? 338838 3 79893 gavinp 2011-01-23 22:18:49 -0800 Created attachment 79893 Patch 338839 4 79893 gavinp 2011-01-23 22:21:56 -0800 Comment on attachment 79893 Patch I had some time on a flight today, and hammered out this test. Unfortunately, it fails right now; as you can see if you run it, the request for the IMG is launched no matter what. I poked at fixing it a bit, and there's something about how early the ImageLoader is consed up is our source of trouble: the capture isn't established the first time that ImageLoader::updateFromElement is called. 466197 5 aestes 2011-09-13 01:56:43 -0700 I noticed this when working on the patch for bug 45586. ImageLoader calls CachedResourceLoader::requestImage() before any beforeload work is performed. For the image case, beforeload only has the opportunity to stop a renderer from being attached to an image, not to stop the network request. This makes beforeload work differently for images than it does for other resources (e.g. beforeload can actually block the network request of an <object> or <embed>). 476235 6 darin 2011-09-30 12:15:27 -0700 Retitled based on my understanding of what’s going on here. 476238 7 darin 2011-09-30 12:16:33 -0700 But as Alexey pointed out, there’s a second issue because of preloading, so maybe my title change does not capture the entire issue here. 490356 8 aestes 2011-10-25 14:18:53 -0700 <rdar://problem/10343617> 490360 9 aestes 2011-10-25 14:23:51 -0700 Removing 'REGRESSION: ' from the title since I believe this bug has existed since beforeload was first implemented. 550206 10 aestes 2012-02-06 12:45:03 -0800 Marking NTBF since this could only be resolved by disabling preload scanning for images. 79893 2011-01-23 22:18:49 -0800 2011-01-23 22:21:56 -0800 Patch bug-52581-20110123221847.patch text/plain 6441 gavinp ZGlmZiAtLWdpdCBhL0xheW91dFRlc3RzL0NoYW5nZUxvZyBiL0xheW91dFRlc3RzL0NoYW5nZUxv 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