OptionalbarsOptionaldragexternalId of the line being dragged (active state), if any.
OptionalhoverexternalId of the primitive hit under the pointer (hover state), if any.
OptionalreadoutThe pane's primary visible price series scale, including a moved left axis.
The pane's primary price series, for a primitive that needs what price actually did rather than just the scales — a forecast scoring itself, say. Lazy, so nothing pays for it unless asked. Absent on synthetic contexts.