One level's resolved style, for a host rendering its controls.
Patch one level. The two toggles move independently: neither implies the other.
Patch several levels, plus the shared options, in one repaint.
Feed a live top-of-book quote; null clears it and the bid/ask levels go inert.
Level prices as of the last frame. Values depend on the viewport, so they are computed while drawing; before the first frame every level reads null. A host that needs them without a chart calls computePriceLevels.
Whether a level has data in the current context. False is the signal to render its control disabled rather than to hide it: "no previous session yet" is information, an absent checkbox is not.