One cell of Visualize.Components.Board (spec/15 §9.1): placed on the grid, one tab
stop carrying data-vis-cell, its chart wrapped in CrosshairHook, BrushHook and
KeyboardHook, and its state drawn over or instead of the chart. Updated by
Visualize.Components.Board.forward/2 with a Visualize.Board.View; never blank, a
cell with no view yet shows :loading.
Its chart's KeyboardHook pushes pick here (spec/15 §13): the board answers the
row behind the point, and the cell opens its drill target through the page, as the
:drill event, or selects the datum's identity across the board.
Its chart's TooltipHook pushes a mark's click here as visualize_event (D-161,
D-170), carrying the view's drawn token: the cell's process resolves it against the
drawing it holds (Visualize.Board.Server.event/3), and the page is sent the
resolved Visualize.Event. A click it cannot resolve sends nothing.