RotateGestureDetector getRotationDegreesDelta returns values close to 360 on small angle change

[stanleyguevara]

Performing minuscule rotations while having rotation line between fingers horizontal causes to getRotationDegreesDelta to output values close to 360, e.g. -359.4 or 359.2.

This is caused by Math.atan2 used to calculate diff angle having ambiguity around +-180*. All is fine and well when performed rotation is shown 1:1 on screen, but I'm scaling it to get more precise moment with small values, so when the received values are 0.015, 0.020, 0.017, -359.4, 0.021... it causes a sudden jerk.

IMO it's a bug because nobody expects sudden 360 for minuscule finger motion when calling getRotationDegreesDelta. The real change of angle is certainly NOT a 360 degree.

My workaround was:

val raw = detector.rotationDegreesDelta
val diffRotation = if (abs(raw) > 300) {   // or some other arbitrary value above 180*
    if (raw < 0) {
        360 + raw
    } else {
        raw - 360
    }
} else raw

I think better fix (without arbitrary 300* value) can be done on library side by checking if one angle falls close to 180* and other close to -180*, so it's passing through discontinous part of Math.atan2 and can be accounted for.