P4 Description
Region has floor and ceiling functions that ensure that calling them twice in a row will yield the same result:
ceil(x) = ceil(ceil(x))
However, due to use of a constant `EPSILON` which is added/subtracted before doing the rounding, this only works for small numbers (in the range of 0-50 approximately). For larger values and scales, rounding errors can easily occur. This is visible as artifacts on screen where controls are a pixel wider than they should be.
The use of the `EPSILON` constant is incorrect, as its value depends on the magnitude of the value in question (as magnitude increases, the fractional precision decreases).
The Math class offers the function `ulp` that should be used here. It represents the smallest possible change in value for a given double.
Extending the existing test case `snappingASnappedValueGivesTheSameValueTest` to use larger magnitude numbers exposes the problems.
ceil(x) = ceil(ceil(x))
However, due to use of a constant `EPSILON` which is added/subtracted before doing the rounding, this only works for small numbers (in the range of 0-50 approximately). For larger values and scales, rounding errors can easily occur. This is visible as artifacts on screen where controls are a pixel wider than they should be.
The use of the `EPSILON` constant is incorrect, as its value depends on the magnitude of the value in question (as magnitude increases, the fractional precision decreases).
The Math class offers the function `ulp` that should be used here. It represents the smallest possible change in value for a given double.
Extending the existing test case `snappingASnappedValueGivesTheSameValueTest` to use larger magnitude numbers exposes the problems.
