On Jun 8, 2014, at 6:38 AM, Benoit Jacob <jacob.benoi...@gmail.com> wrote:
> Note that the current way that isIdentity() works also fails to offer that > characteristic, outside of accidental cases, due to how floating point > works. DOMMatrix focuses on CSS, SVG and HTML which are not limited to value range of -1 to 1. Values of 2, 4, 100 or values with x.5, x.25 are much more likely to occur. For these cases, translation and untranslation is more likely an identity matrix again. Same for scale and unscale. Of course, transformations with rotation are more likely to create a matrix that is close to identity but not exactly identity. We can not prevent deviations on matrix transformations. We can not even prevent deviation on simple operations like multiplication or division. A visual example was posted on public-fx was: "" "Math.sqrt(x)*Math.sqrt(x) === x" evaluates to false if x isn't a perfect square (integer or not). "" This is still no issue though. As said before, the purpose of isIdentity() is to optimize code. And isIdentity() can be used to optimize all cases that can be optimized by roc's and Rik's proposed method plus many more (if not the vast majority) of actual real world use cases. In the worst case, the optimization does not happen which wouldn’t without isIdentity() anyway. Greetings, Dirk _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
