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Re: quick comments on Matrix

From: Dirk Schulze <dschulze@adobe.com>
Date: Thu, 14 Mar 2013 21:51:54 -0700
To: "robert@ocallahan.org" <robert@ocallahan.org>
CC: "public-fx@w3.org" <public-fx@w3.org>
Message-ID: <9CE60178-5B7F-412C-AF1F-C4B4FEC91EEF@adobe.com>
Hi Rob,

Thank you very much for your early feedback. I incorporated your feedback with the latest commit[1]. See inline comments:

On Mar 13, 2013, at 7:06 PM, Robert O'Callahan <robert@ocallahan.org> wrote:

> https://dvcs.w3.org/hg/FXTF/raw-file/default/matrix/index.html
> 
> In the array/sequence Matrix constructors, what happens if the length of the array/sequence is not 6 or 16?

That was missing. For now a DOMException with name SyntaxError is thrown.

> 
> In the string constructor, what happens if the string is not valid?

Ditto, if the string does not parse to a CSS transform list.

> 
> Why don't you add the default parameters for Matrix methods such as scaleBy to the WebIDL directly?

This is fixed now.

> 
> In rotateFromVector(By), what happens if the x or y coordinate is zero? Actually it's not clear to me why these can't be zero.

This was taken over from SVG. The calculation is "(+/-) atan(y/x)". While y could be zero, x can't. I assume the editors of SVG wanted to have consistency between the values.

> 
> I assume toFloat32/64Array always return a 16-element array but this should be stated.

This is fixed now.

> 
> What's the rationale for using double for matrix elements? Are implementations allowed to use 32-bit precision internally?

WebIDL requires a datatype for attributes. In this case there was the choice between float (32-bit precision) and double (64-bit precision). The later seems to make more sense - especially because of Float64Array.

Greetings,
Dirk

[1] https://dvcs.w3.org/hg/FXTF/rev/5a64938d0a49

> 
> Rob
> -- 
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Received on Friday, 15 March 2013 05:00:24 GMT

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