The figure, read for its active subplot when it moves
Readonlysize: numberHow many subplots it has; one has no lobby, and its panel is not named
ReadonlyactiveSubplot: { traces: readonly (readonly { getId: () => string }[])[] }The subplot the lobby is on
Readonlytraces: readonly (readonly { getId: () => string }[])[]Its layers, one row per layer
The adapter's navigate callback
An observer to register on the figure
Build the observer that tells a navigate callback the reader is in the figure lobby, and on which subplot.
Leaving a subplot makes the figure active rather than a trace, so the trace observers go quiet and say nothing about having stopped. A consumer drawing an overlay would keep the last point highlighted and carry it to whichever panel the reader moved to next, so the figure reports the selection ending with
null. It names the subplot the lobby is on beside it: MAIDR outlines that panel itself only where it finds one in the page, and a chart drawn on a canvas has none to find, so the consumer is the only one that can.