RFR: 8311895: CSS Transitions [v2]

[John Hendrikx]

On Mon, 31 Jul 2023 18:01:31 GMT, Michael Strauß <mstrauss at openjdk.org> wrote:

>> modules/javafx.graphics/src/main/java/com/sun/scenario/animation/StepInterpolator.java line 73:
>> 
>>> 71:         }
>>> 72: 
>>> 73:         if (t >= 0 && step < 0) {
>> 
>> `t >= 0` always holds, perhaps the original `t` was meant here?  The `t` parameter is re-assigned, which may be confusing.
>
> This algorithm is implemented as [specified](https://www.w3.org/TR/css-easing-1/#step-easing-algo), which accounts for the possibility that the interpolator is used for a back-filling animation (`t < 0`). While this is not possible in JavaFX (but may be possible in the future), I think it makes sense to keep the algorithm as is, because it ensures that its results are always correct, even though negative values for `t` are currently out of spec.

Yeah, I figured as much.  I just don't like code that you can't get covered in a unit test, or that contradicts itself.  As you can see, I was confused, is it a bug or a feature?  Perhaps a comment then to indicate that it's intentional.

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PR Review Comment: https://git.openjdk.org/jfx/pull/870#discussion_r1280678762