transformDeltaViaPositions static method
Transforms untransformedDelta
into the coordinate system described by
transform
.
It uses the provided untransformedEndPosition
and
transformedEndPosition
of the provided delta to increase accuracy.
If transform
is null, untransformedDelta
is returned.
Implementation
static Offset transformDeltaViaPositions({
required Offset untransformedEndPosition,
Offset? transformedEndPosition,
required Offset untransformedDelta,
required Matrix4? transform,
}) {
if (transform == null) {
return untransformedDelta;
}
// We could transform the delta directly with the transformation matrix.
// While that is mathematically equivalent, in practice we are seeing a
// greater precision error with that approach. Instead, we are transforming
// start and end point of the delta separately and calculate the delta in
// the new space for greater accuracy.
transformedEndPosition ??= transformPosition(transform, untransformedEndPosition);
final Offset transformedStartPosition = transformPosition(transform, untransformedEndPosition - untransformedDelta);
return transformedEndPosition - transformedStartPosition;
}