Optional ReadonlytransformAdjusts the measured size before it is written to the graph element, e.g. to
add padding or reserve space for a header. Receives the measured dimensions
plus the element's current layout (TransformElementLayoutParams) and
returns the width/height (and optionally x/y) to apply.
Options for useMeasureElement, controlling how the measured DOM size is turned into the graph element's size.