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Re: canvas: globalAlpha should not throw

From: Philip Taylor <pjt47@cam.ac.uk>
Date: Wed, 10 Jun 2009 17:57:11 +0100
Message-ID: <4A2FE5E7.6010106@cam.ac.uk>
To: Ian Hickson <ian@hixie.ch>
CC: Simon Pieters <simonp@opera.com>, "public-html@w3.org" <public-html@w3.org>
Ian Hickson wrote:
> On Tue, 19 May 2009, Simon Pieters wrote:
>> The spec doesn't call out NaN and Infinity for globalAlpha. I think 
>> globalAlpha should be handled consistently with the other canvas 
>> attributes and not throw an exception.
>> http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html#dom-context-2d-globalalpha
> The spec says:
>    Unless otherwise stated, for the 2D context interface, any method call 
>    with a numeric argument whose value is infinite or a NaN value must be 
>    ignored.
> ...and doesn't appear to contradict this in the definition of globalAlpha. 
> Am I missing something?

Unless I'm missing something: globalAlpha isn't a method call.

("Common conformance requirements" differentiates "DOM attribute" 
assignment from "method" calling, so I presume that distinction is real, 
and the bit you quoted from the spec only talks about method calls.)

Philip Taylor
Received on Wednesday, 10 June 2009 16:58:35 UTC

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