Summary:
The Math Strikes Back
Several related things:
* When we specify `scale: 0;` style for some view it ends up with calling `CATransform3DScale` with zero scale parameter.
* In this case `CATransform3DScale` returns transform matrix full of zeros. It actually depends on representation and matrix-type (2d or 3d) but in UIView debugger it appears as [0, 0, 0, 0, ...]. And probably it is correct result.
* By default, for hit-testing, UIKit uses specially optimized logic based on GPU/CALayer infrastructure under the hood. And the transform matrix full of zeros breaks this algorithm. I guess, it happens because zero-matrix doesn't quite make sense.
So, `scale: 0;` is a weird edge case, and in this diff, we are trying to illuminate it by replacing with epsilon value.
Related SO issues:
http://stackoverflow.com/questions/25964224/cgaffinetransformscale-not-working-with-zero-scalehttp://stackoverflow.com/questions/7937369/animate-uiview-scale-to-zero
Reviewed By: blairvanderhoof
Differential Revision: D4734475
fbshipit-source-id: 7241cdffa86c05a6552860a25789e2281588ba23
64c327ae68