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Re: Relaxing SVGList* item object equality in Blink/Chromium

From: Kouhei Ueno <kouhei@google.com>
Date: Thu, 12 Dec 2013 10:58:00 +0900
Message-ID: <CAPVAxLWgsd0Y48nd=5o-Cc9Y8ytzhLGREeonSYf5uYS5pd6fng@mail.gmail.com>
To: robert@ocallahan.org
Cc: www-svg <www-svg@w3.org>
> For example, does this mean svgElement.x !== svgElement.x? Or
> svgElement.x.baseVal != svgElement.x.baseVal?

I want to drop guarantees about svgElement.x === svgElement.x, and
svgElement.x.baseVal === svgElement.x.baseVal. They may ===, but it
may not be all the time.
But of course, their values are guaranteed to be equal:
svgElement.x.baseVal.value === svgElement.x.baseVal.value

2013/12/12 Robert O'Callahan <robert@ocallahan.org>:
> On Tue, Dec 10, 2013 at 8:16 PM, Kouhei Ueno <kouhei@chromium.org> wrote:
>>
>> I am refactoring SVG DOM implementation in Blink/Chromium.
>> I would like to notify about an upcoming change in SVGList*
>> implementations.
>>
>> In the current implementation in Blink, we follow the spec stating
>> that "the inserted item is the item itself and not a copy" by
>> returning exactly the same item object. Thus, the javascript object
>> returned from the list is ensured to === the original object inserted
>> into the list.
>>
>> http://www.w3.org/TR/SVG2/single-page.html#types-__svg__SVGLengthList__initialize
>>
>> For example, "===" operator currently returns true for the following code:
>> var a = svg.createSVGLength();
>> var b = list.initialize(a);
>> console.log(a === b) // shows "true".
>>
>> However, we are considering to change our behavior here. We would like
>> to return different javascript objects when retrieving list items.
>> Considering the previous example, the new implementation would return
>> a different javascript object for "b", thus making "a !== b".
>
>
> It's not clear from that discussion exactly what would be affected.
>
> For example, does this mean svgElement.x !== svgElement.x? Or
> svgElement.x.baseVal != svgElement.x.baseVal?
>
> Rob
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-- 
Kouhei Ueno
Received on Thursday, 12 December 2013 08:20:19 UTC

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