void SkEvalCubicAt(const SkPoint src[4], SkScalar t, SkPoint* loc,
SkVector* tangent, SkVector* curvature) {
SkASSERT(src);
SkASSERT(t >= 0 && t <= SK_Scalar1);
if (loc) {
loc->set(eval_cubic(&src[0].fX, t), eval_cubic(&src[0].fY, t));
}
if (tangent) {
// The derivative equation returns a zero tangent vector when t is 0 or 1, and the
// adjacent control point is equal to the end point. In this case, use the
// next control point or the end points to compute the tangent.
if ((t == 0 && src[0] == src[1]) || (t == 1 && src[2] == src[3])) {
if (t == 0) {
*tangent = src[2] - src[0];
} else {
*tangent = src[3] - src[1];
}
if (!tangent->fX && !tangent->fY) {
*tangent = src[3] - src[0];
}
} else {
tangent->set(eval_cubic_derivative(&src[0].fX, t),
eval_cubic_derivative(&src[0].fY, t));
}
}
if (curvature) {
curvature->set(eval_cubic_2ndDerivative(&src[0].fX, t),
eval_cubic_2ndDerivative(&src[0].fY, t));
}
}
void SkEvalCubicAt(const SkPoint src[4], SkScalar t, SkPoint* loc, SkVector* tangent, SkVector* curvature)
{
SkASSERT(src);
SkASSERT(t >= 0 && t <= SK_Scalar1);
if (loc)
loc->set(eval_cubic(&src[0].fX, t), eval_cubic(&src[0].fY, t));
if (tangent)
tangent->set(eval_cubic_derivative(&src[0].fX, t),
eval_cubic_derivative(&src[0].fY, t));
if (curvature)
curvature->set(eval_cubic_2ndDerivative(&src[0].fX, t),
eval_cubic_2ndDerivative(&src[0].fY, t));
}
