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Re: <canvas> and the 2D context API

From: Shelley Powers <shelleyp@burningbird.net>
Date: Thu, 13 Aug 2009 11:53:35 -0500
Message-ID: <4A84450F.7000704@burningbird.net>
To: Anne van Kesteren <annevk@opera.com>
CC: Toby Inkster <tai@g5n.co.uk>, Maciej Stachowiak <mjs@apple.com>, Sam Ruby <rubys@intertwingly.net>, Adrian Bateman <adrianba@microsoft.com>, David Singer <singer@apple.com>, Dan Connolly <connolly@w3.org>, "public-html@w3.org" <public-html@w3.org>
Shelley Powers wrote:
> Anne van Kesteren wrote:
>> On Thu, 13 Aug 2009 17:59:48 +0200, Toby Inkster <tai@g5n.co.uk> wrote:
>>  
>>> On Wed, 2009-08-12 at 18:29 -0700, Maciej Stachowiak wrote:
>>>    
>>>> But HTML5 would likely have a normative reference to a Canvas API
>>>> spec, so there is a limit. Per W3C rules, you can't normatively
>>>> reference a document that's more than one maturity level apart.
>>>>       
>>> The solution then seems to be to only include an informative reference.
>>> An example of the current draft with just an informative reference to
>>> the canvas API might be:
>>>
>>> http://buzzword.org.uk/2009/html5/the-canvas-element-20090813.html
>>>     
>>
>> This does not help postMessage(), which takes an ImageData object.
>>
>>
>>   
> Is that the only instance where the HTML 5 specification drills down 
> into the Canvas element's 2D API directly?
>
> Again, this is a handshake issue, whereby one requirement the HTML 5 
> specification would have is the ability to obtain a serialization of 
> the Canvas object. This is an unfortunate consequence of merging and 
> breaking down borders between API and declarative syntax, but I don't 
> see it as a showstopper.
>
> There's nothing in this _requirement_ that would overly inhibit 
> innovation on the Canvas object. Nor is there anything likely to 
> happen with the Canvas object, the 2D immediate mode API, that would 
> impact on this handshake between specifications.
>
> But you are right, in this would be normative, not informative. I 
> don't see this as a showstopper though, unless we're constrained by 
> HTML 5 not being able to specify a normative reference to the new 2D 
> API, because the 2D API doesn't have a published specification yet.
>
> In which case, I would think it better to remove the reference to 
> ImageData from PostMessage. It could be taken up again in a later HTML 
> specification, as folks are fond of saying. I've looked at the 
> existing implementations of PostMessage for the various browsers. None 
> have implemened ImageData yet. Even if they had, this is the risk they 
> take for implementing what's current in a working draft.
>
> As Philipe stated in the HTML-WG IRC, implementations may not support 
> passing ImageData objects directly[1], at least with Worker Threads.
>
> This is not a showstopper.
>
> Shelley
>
> [1] http://krijnhoetmer.nl/irc-logs/html-wg/20090802#l-61
>
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Or I should say, I couldn't find anything about ImageData and 
PostMessage in the documentation (alpha/beta/otherwise) I checked out.

Shelley
Received on Thursday, 13 August 2009 16:54:39 UTC

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