[Webkit-unassigned] [Bug 82956] [chromium] TransformationMatrix::to2dTransform seems unnecessary in LayerRendererChromium

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=82956





--- Comment #3 from Shawn Singh <shawnsingh at chromium.org>  2012-04-02 16:56:40 PST ---
(In reply to comment #2)
> (In reply to comment #1)
> 
> Haha, I realize this is exactly the same as the first thing you quote from me.  I think maybe I had some thought that not dropping the 3d transform part of the matrix would result in a different value when you projected back since you'd flattened that point to 2d and inflated in 2d.
> 
> Tests would certainly be helpful at this point in the conversation.

Well, there might be a correctness difference on the inverse.   So the question I see is:

is it true that  transform.to2dTransform().inverse().mapPoint() == transform.inverse().projectQuad() ??

And, assuming the answer is "no they are not equal", then we should ask which one is correct to use for our code.

As per offline discussion with Enne, I'll toy with some example tests on this, and report back answering these questions.

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