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Re: [FileAPI] createObjectURL isReusable proposal

From: Charles Pritchard <chuck@jumis.com>
Date: Thu, 02 Feb 2012 22:51:21 -0800
Message-ID: <4F2B83E9.9000801@jumis.com>
To: Bronislav Klučka <Bronislav.Klucka@bauglir.com>
CC: public-webapps@w3.org
On 2/2/12 10:40 PM, Bronislav Klučka wrote:
>
>
> On 3.2.2012 7:34, Bronislav Klučka wrote:
>>
>>
>> On 28.1.2012 8:47, Ian Hickson wrote:
>>> On Sat, 28 Jan 2012, Kyle Huey wrote:
>>>> On Sat, Jan 28, 2012 at 7:10 AM, Darin Fisher<darin@chromium.org>  
>>>> wrote:
>>>>> I'm not sure what a concrete proposal would look like.  Maybe
>>>>> Element.URL.createObjectURL or just Element.createObjectURL?
>>>> Wouldn't returning an object (which can be GCd) be a better solution?
>>> The whole point of the API is that we have an object but need a 
>>> string (a URL).
>>>
>>
>> We could always leave the revokeObjectUrl call to simply delete 
>> content from cache...
>>
>> Brona
>>
>
> BTW. I know It sounds a lot like something that can be done with 
> FileSystem API, but I hope the ease and benefits for developers are 
> clear here, FileSystem API would be overkill for this (and easier to 
> implement for vendors without FileSystem API implemented yet)
>
> Brona

Yes, revokeObjectURL would simply mark the content as "dirty". Some 
other cache / trash cleanup takes care of the garbage.
There's nothing in createObjectURL that says a Blob must be in RAM.

For all intents, createObjectURL could put items into the Temporary 
FileSystem for a domain. The Chromium team has already lifted file size 
limitations on the temporary file system. That's with the understanding 
that items can be evicted at any time.

However, createObjectURL specifies that an object may not be evicted 
until the page is navigated away from, or until revokeObjectURL is called.
Persistence is typically limited to 5MB per domain. Or something like 
10MB when localStorage is added to the mix.

It seems like this is an interesting middle-ground.

The battle is in the CSS-realm.

With the <img> tag, we can simply hook into onerror. Within CSS, we are 
unaware as to whether our contested resource has been loaded.
There are of course, iframe tricks, which are used for font loading.

Lots of subtleties in this area.

I see no reason why an author should expect to stash 100MB of objects 
into createObjectURL, nor any reason why a UA could not manage 100MB for 
the application lifetime; the user can certainly be informed, as they 
are with other APIs, if the limit has gone beyond what the UA is 
comfortable with. That's always useful for debugging/development -- when 
infinite loops are a normal part of the web experience.


-Charles
Received on Friday, 3 February 2012 06:51:46 GMT

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