[MarkusNeusinger]

Summary

• page.waitForFunction(fn, { timeout: 2500 }) in automation/js-render/render.mjs put the options object in Playwright's argument slot, so every snippet that never sets window.__anyplotReady (1,250 of the 1,294 JavaScript implementations) waited through the 30 s default before the fonts-ready fallback ran.
• The options now sit in the third slot, waitForFunction(fn, null, { timeout: 2500 }), and a snippet that cannot send the signal at all (its source does not name __anyplotReady and it is not the React entry) settles directly instead of idling through the 2.5 s timeout. Same fallback, same screenshot, same checks.
• Found by the Highcharts 13 before/after pass (chore(js): bump Highcharts to 13.1.1 #12246): a full catalogue render of one library took about 22 minutes at 16 parallel, almost all of it in this wait.

Plan

N/A

Test plan

• plots/bar-basic/implementations/javascript/{chartjs.js,echarts.js,muix.tsx} rendered with the harness from main and from this branch, PNGs compared with ImageChops.difference (bbox None = identical, 3200×1800):

  Snippet	Signal path	main	this branch
  chartjs (no signal)	settle directly	30.8 s	1.6 s
  echarts (finished handler)	wait, then settle	31.0 s	3.1 s
  muix (React entry)	wait, signal arrives	—	0.75 s

  Note: the ECharts snippet runs into the 2.5 s timeout on both versions, so its chart.on("finished") signal never fires under animation: false; the PNG is identical either way. The 44 snippets that name the signal therefore still pay up to 2.5 s; a follow-up could fire the signal from the harness after ECharts' finished or drop the handler contract. Not changed here.

• uv run python -m tools.changelog check --base origin/main passes.

• CI job "Build renderer image and render through the harness" green on the first commit; re-run on this head.

• Gemini 3.8 Flash first review: verdict "sound with changes"; its one finding (skip the wait when the signal cannot arrive) is applied in the second commit. Copilot next.

[Copilot]

🟢 Approval recommended

The reviewed changes have no unresolved issues that would block approval.

No open issues 🎉

What changed in this PR

This pull request fixes the JavaScript render harness so Playwright applies the intended 2.5-second ready-signal timeout instead of the 30-second default.

Changes:

• Corrects the waitForFunction argument order by passing null before the timeout options.
• Documents the timeout fix and resulting render-time improvement.

File	Description
changelog.d/​js-render-ready-timeout.md	Documents the JavaScript render timeout correction and performance benefit.
automation/​js-render/​render.mjs	Corrects the Playwright timeout argument placement for render readiness.

_{Review effort: Lite}