ChangeAnchorPoint

Overview

Change the anchor point of a target.

Contract

The anchor point of the view is immediately changed to the newAnchorPoint. The target's position is also updated to avoid noticeable movement of the target.

Plan ChangeAnchorPoint {
  Position newAnchorPoint
}

newAnchorPoint should be relative to the target's dimensions. E.g. an anchor point of 0,0 means the corner of the target should be the new anchor point.

Performer considerations

The following diagram shows the desired effect of changing the anchor point of an element:

In pseudo-code:

func onGestureInitiated() {
  let initialPositionInElement = Point(element.anchorPoint.x * element.width,
                                       element.anchorPoint.x * element.height)

  let gesturePositionInElement = gesture.positionInElement(element)
  let desiredAnchorPoint = Point(gesturePositionInElement.x / element.width,
                                 gesturePositionInElement.y / height)

  element.anchorPoint = desiredAnchorPoint
  element.position += gesturePositionInElement - originalPositionInElement
}