The old lines were our hand-rolled shortcut: every arrow from the
source's bottom-center to the target's top-center as a single S-bezier.
Dagre actually routes each edge as border-intersected waypoints that
leave/enter nodes on whatever side the route needs — mermaid's
behavior. We now keep that routing (owner: adopt it).
blockLayout also returns edgePts — dagre's per-edge waypoint lists.
edgePathD draws them through d3's curveBasis, the exact recipe
dagre-d3's own renderer uses (and mermaid's default flowchart curve):
endpoints repeat so the line starts at the source border and the END
pulls back by the tip overhang so the arrowhead's tip lands on the
target border with its mouth at the path's end. Pinned in tests.
Dangling/unroutable edges draw nothing. d3-shape added as a direct
dependency (^3.2.0, already in the tree via dagre-d3-es — lane touch,
flagged to master with dagre-d3-es).
amosblomqvist
0f6b2d5c1e