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Re: [whatwg] [canvas] Proposal for supportsContext

From: Tobie Langel <tobie.langel@gmail.com>
Date: Mon, 10 Sep 2012 21:44:09 +0200
Message-ID: <891674873124299893@unknownmsgid>
To: Dean Jackson <dino@apple.com>
Cc: "whatwg@lists.whatwg.org" <whatwg@lists.whatwg.org>
On Sep 10, 2012, at 9:32 PM, Dean Jackson <dino@apple.com> wrote:

>
> On Sep 10, 2012, at 12:28 PM, Tobie Langel <tobie.langel@gmail.com> wrote:
>
>> On Sep 10, 2012, at 8:14 PM, Dean Jackson <dino@apple.com> wrote:
>>
>>> I propose adding a new method to HTMLCanvasElement:
>>>
>>> interface HTMLCanvasElement : HTMLElement {
>>> boolean supportsContext(DOMString contextId, any... arguments);
>>> };
>>>
>>> supportsContext takes the same parameters as getContext, and simply returns
>>> true if the corresponding call to getContext would have returned a valid
>>> context, false otherwise.
>>
>> What about enabling feature detection by providing a method per context?
>>
>> interface HTMLCanvasElement : HTMLElement {
>> object get2DContext();
>> object getWebGLContext(any... args);
>> };
>>
>> That way, developers can use idiomatic JS for feature testing like
>> pretty much everywhere else on the Web platform:
>>
>> if (canvas.get2DContext) {
>> // do stuff with 2D canvas
>> }
>
> This doesn't address the problem we are hitting, which is that
> it is expensive to create a context.

It does. Only expose the API when you can create the context.

> It's also a big change to
> an existing operational API.

Agreed. You can always leave the previous method around for backward
compatibility.

--tobie
Received on Monday, 10 September 2012 19:44:42 UTC

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