pangenome-range

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ADR 0003: implement a small reference-anchored SVG renderer ​

  • Status: accepted
  • Date: 2026-08-27

Context ​

The first demo used a general Canvas controller and exposed multiple product modes around a dense raw graph. The replacement needs a recognizable tube map, DOM hit targets, crisp sequence labels, bounded complexity, and no backend.

SequenceTubeMap was inspected at its current vgteam/sequenceTubeMap source, including src/util/tubemap.js and its React wrapper. Its MIT license permits reuse, and its reference-first ordering, curved paths, orientation marks, redundant-node handling, and hover emphasis are useful interaction precedents. The core, however, is a mutable module of more than 5,000 lines coupled to D3, deep-copied VG tracks and reads, React application state, and broader track and server infrastructure. Extracting it would require a compatibility layer larger than the bounded renderer needed here.

Decision ​

Implement a local framework-neutral pipeline:

text
buildTubeMapModel() -> layoutTubeMap() -> renderTubeMapSvg()

The real reference traversal fixes horizontal order. Alternate components use deterministic reference attachments and lanes; there is no force simulation. SVG supplies accessible node and pattern hit targets. The adapter, not the renderer, owns deterministic pattern selection, tile-local identifiers, structural collapse, provenance, and refusal limits.

No SequenceTubeMap source was copied or adapted. Consequently this change does not add a third-party code notice. The project license remains unchanged.

Consequences ​

The public viewer bundle is substantially smaller and no longer imports the old Canvas application. The renderer is intentionally less general than SequenceTubeMap and currently uses display-oriented structural bundles for complex fixed-window payloads. Exact node membership remains inspectable, but the collapsed shape is not an exact genomic-length encoding. A future renderer change must preserve the framework and transport boundaries and must be backed by a new golden fixture and browser evidence.