[XDGFX]

Summary

A pipe can set coil: true to show it is one long looped length, such as an underfloor heating loop. Each of its runs draws as six passes back and forth, label above.

 pipes:
   pex_16mm_underfloor:
     label: 16MM PEX UNDERFLOOR HEATING LOOP
     size: 16mm
+    coil: true        # anything but true or false is an error

layoutElk
  turnNode(w)            # pipe^: node sized for the passes, legs one coil span apart
    coilTurn             # six level passes in place of the plain turn
  slot(w)                # straight run: inline label slot, tall enough for the coil
    coilInline           # coil let into the level stretch through the slot,
                         # or undefined -> the run draws plain

The coil is only extra points on the route, so render.ts is untouched: corners are filleted, and colour and weight are the pipe's own. A run with an open end is a card and never coils.

Evidence

• Before: pex_16mm_underfloor^ in a real heating plan drew as a plain U-turn with its label beside the bend.
  After: the same plan with coil: true draws six orange passes east of the two PEX adapters, label above the first pass. A straight coiled run, labelled and unlabelled, was rendered and checked by eye as well.
• Sheets without coil are byte-identical: all 14 SVGs and 10 Markdown tables of the project that uses ferrule (4 plumbing plans, 10 looms) were rendered from this branch and compared with cmp against the committed ones, 0 differ.
• npm run typecheck, npm test (85 pass, 4 new) and npm run build pass.

test/coil.test.ts
  a coiled turn runs out and back in evenly spaced passes, east of both its ends
  a coiled straight run crosses its own line in passes, between ends that stay where they were
  a coiled pipe with no label still coils, and draws no label
test/pipeviz.test.ts
  a pipe is coiled only when it asks, and any other coil value is an error

Not covered by a test: the plain-line fallback on a straight run, which no small plan could be made to trigger.

Merge Danger

Door: two-way

Opt-in key; reverting removes it and nothing else.

Blast Radius: none-unless-opted-in

A plan that already carries a stray non-boolean coil on a pipe now fails to render.

🤖 Generated with Claude Code