Two custom canvas layers around sigma's own stack (DOM order: hulls
behind everything; region labels above nodes, below node labels).
Per cluster (vision section 1): convex hull (monotone chain) of member
viewport positions, offset outward 14px, rounded corners, a blurred
low-opacity fill (ctx.filter, graceful degrade to flat fill) plus a
dashed boundary stroke, and the LLM label at the centroid. Stable hue
per cluster id (content hash) — a region keeps its color across
reshuffles because the id only changes when the members do.
Geometry is a pure function of positions at draw time: every
afterRender re-derives hulls through the current camera, so pan/zoom/
relayout can never invalidate it (the boundary decision pays off: no
stored geometry, nothing to recompute after a future physics change).
The inverse gate: the cluster label layer's opacity is the exact
complement of the node-label layer's over the fade span of THE zoom
control (labelZoom, default 0.5x) — the two label systems never
coexist.
Live-verified in the browser: hulls painting behind edges; region
labels above nodes; zoom-in crossfades cluster 1 -> 0 as node labels
0 -> 1 (0.176 + 0.824 mid-fade); zoom-out restores; hull pixel count
changes with zoom (geometry follows the camera); zero console errors;
layers removed on renderer teardown. 372/372 tests, typecheck, lint,
build green.
Also named the real graph: one 11.5s labeler call minted all 32
region labels for the 338-node notes graph (Relational Databases & SQL,
Differential Forms, Sales as Uncertainty Reduction, ...).
amosblomqvist
71a17c5e0d