Fix scatter collapse after repeated box zoom

[FarhanAliRaza]

Motivation

Repeated anisotropic box zoom followed by Zoom Out could collapse a scatter plot into a horizontal band.

A box zoom can narrow X and Y by very different factors. Zoom Out previously expanded both axes geometrically without respecting each axis's original range, so the less-zoomed axis could grow far beyond its home span while the other axis was still zoomed in. That extreme aspect-ratio mismatch visually flattened the point cloud.

Description

• Cap each axis independently at its original span during zoom-out. Once an axis reaches its home span it stops expanding, while a more deeply zoomed axis can continue zooming out. (js/src/53_interaction.js)
• Add the exact repeated box-zoom reproduction to examples/demo-advance.ipynb.
• Add a Chromium regression that performs three anisotropic box zooms and four zoom-outs, then verifies X remains zoomed while Y stops exactly at its home domain. (tests/test_zoom_precision.py)
• Regenerate the tracked anywidget and standalone browser bundles from the JS source. (python/xy/static/index.js, python/xy/static/standalone.js)

The earlier GPU-coordinate precision workaround was removed because it was not needed for this failure.

Testing

• node js/build.mjs --check — generated static bundles are fresh.
• uv run ruff check tests/test_zoom_precision.py — passed.
• uv run ruff format --check tests/test_zoom_precision.py — passed.
• uv run pytest tests/test_zoom_precision.py tests/test_static_client_security.py tests/test_scatter.py tests/test_components.py -q — 187 passed.
• Chrome verification using the 20,000-point notebook reproduction:
  • after three anisotropic box zooms: X 125×, Y 1.953×
  • after four zoom-outs: X 7.8125×, Y 1×
  • before the fix, Y reached 0.122×—eight times wider than its home span
  • the point cloud remained two-dimensional and no console errors were emitted

---

Closes #87

[codspeed-hq]

Merging this PR will not alter performance

✅ 94 untouched benchmarks
⏩ 1 skipped benchmark¹

---

_{Comparing codex/fix-scatter-view-collapse-on-zoom (83d816c) with main (b283b10)}

Footnotes

1. 1 benchmark was skipped, so the baseline result was used instead. If it was deleted from the codebase, click here and archive it to remove it from the performance reports. ↩

[masenf]

when zooming out, if the zoom level is already at 100%, the pan is reset as well. when this happens, it leaves the previous selection in place including the dot and tooltip.

Screen.Recording.2026-07-20.at.2.54.03.PM.mov

probably a task for another PR, but i'm wondering if we should let the outer page scroll when the chart is already zoomed out to mitigate ENG-10492 which is a bit annoying when browsing the docs. idk if it would be more jarring for a user actively zooming out to hit 100% and then suddenly scroll down the page.