🐛 Y-grid can infinite-loop and freeze the tab on tiny / denormal ranges

[itsdiay]

Summary

pickInterval and drawGrid can fail to terminate when the Y domain is tiny or non-finite, hanging the main thread (browser “Page Unresponsive”).

This pairs with the minRange floor bug (#18): a denormal-scale domain makes fine so small that val += fine never advances. Even with a correct floor, hardening the grid is worthwhile so any pathological range cannot lock up the page.

Failure modes

pickInterval (src/draw/grid.ts)

• Invalid valRange / pxPerUnit (≤0 or non-finite) → bad log10 / division.
• Divisor shrink loop: span /= divs[...] does not strictly decrease → infinite while.
• Runaway iterations on slow shrink.
• best === Infinity or non-positive best → unsafe fallback.

drawGrid fine-label loop

for (let val = first; val <= maxVal; val += fine) { ... }

• fine ≤ 0 or non-finite → loop never reaches maxVal.
• first non-finite.
• fine smaller than ULP of val → val + fine === val → infinite loop.

Suggested guards (minimal)

pickInterval

• Reject non-positive / non-finite inputs early; return a finite default.
• Only shrink when next < span && next > 0; break otherwise.
• Cap iterations (e.g. 1e4).

drawGrid

• Early-return if fine is not finite / ≤ 0.
• Bail if first is non-finite.
• Break when val + fine does not strictly increase.
• Hard iteration cap (e.g. 4096) as a last resort.

Related

• 🐛 Y-axis minRange floor skipped for tiny nonzero spans (can freeze tab) #18 — Y-axis minRange floor skipped for tiny nonzero spans (primary domain-side cause for micro series).

Environment

liveline@0.0.7, React web, micro price series (~1e-4–1e-5).