[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 #4 from Adrienne Walker <enne at google.com>  2012-04-02 17:20:36 PST ---
Based on a simple example, I think my intuition is correct in that inverse.mapQuad != to2DTransform.inverse.mapQuad.  This is because in the process of taking the inverse, the components in the 3rd column of the original matrix end up affecting components other than z in the final matrix.

I think I have also convinced myself that using to2DTransform + inverse.mapQuad is equivalent to just using inverse.projectQuad.

My inclination is to leave this code as-is, given that transform2d + mapQuad is cheaper than projectQuad because it ignores transforming the z-component of every point.

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