private bool TestCrossing(GestureQuad quad, PointF p, PointF p2)
{
var q = quad.C;
var q2 = quad.D;
var r = p2.Subtract(p);
var s = q2.Subtract(q);
var qp = q.Subtract(p);
var rs = r.Cross(s);
// parallel case
if (rs == 0) return false;
var t = qp.Cross(s) / rs;
var u = qp.Cross(r) / rs;
return (t >= 0 && t <= 1 && u >= 0 && u <= 1);
}
public GestureState TestMotion(int index, PointF start, PointF end)
{
if (index >= Points.Count - 1)
{
return GestureState.Complete;
}
var previousPoint = Points[index];
var nextPoint = Points[index + 1];
var previousRadiusSq = previousPoint.threshold * previousPoint.threshold;
var endDX = end.X - previousPoint.X;
var endDY = end.Y - previousPoint.Y;
var endRadiusSq = (endDX * endDX) + (endDY * endDY);
var quad = new GestureQuad(previousPoint, nextPoint);
// first check for point completion
if (TestCrossing(quad, start, end))
{
if (index == Points.Count - 2) return GestureState.Complete;
else return GestureState.Advance;
}
// must be inside the quad or the starting circle
if (!(endRadiusSq <= previousRadiusSq || quad.Test(end))) return GestureState.Fail;
return GestureState.OK;
}