ElbowArrowEdge

One side of a box, as the router sees it.

value is where the side sits on its own axis (a left or right edge has an x, a top or bottom edge has a y); cross is how far the attachment point may slide along the side, and crossTarget is where it would like to sit — the centre, unless a bound anchor asked for somewhere else. expanded is value pushed outwards by ElbowArrowOptions.expandDistance, which is where a leg parallel to the side is allowed to run, or null when the side may not be expanded because the other box is already inside that margin.