BrowserSkill/evals/browser/cases/regression/snapshot-coordinates/README.md

DOMSnapshot layout-unit regression (#195)

Source: https://github.com/Tencent/BrowserSkill/pull/195

DOMSnapshot bounds and document scroll offsets retain Blink layout units. Treating them as CSS pixels changes both positions and sizes under device scaling/browser zoom, before iframe projection or viewport clipping even starts.

The fixture contains a scrolled root, a scrolled same-process iframe, an OOPIF served from the other loopback hostname, and a nested iframe in each. Owners have borders, padding and CSS transforms. The geometry test compares the production capture's local and top-level rectangles against independent DOM border boxes, with at most 2 CSS pixels of layout rounding. It also checks that each target reads layout metrics only once. No credentials or personal tabs are used.

Run the geometric assertions with Node 22+ and a local Chrome executable:

BSK_GEOMETRY_CHROME=/path/to/chrome pnpm --filter @browser-skill/extension exec vitest run \
  src/tools/__tests__/snapshot-coordinates.browser.test.ts

The test launches and cleans up its own headless Chrome profiles. It explicitly verifies the requested browser zoom and OOPIF topology, so unsupported setups fail rather than silently testing a different configuration. It is skipped in ordinary unit runs unless the executable is specified. No browser download or new package dependency is required.

The corpus smoke case checks fixture readiness and observable semantics through the real CLI:

BSK_AUTO_UPDATE=off pnpm eval:browser smoke --case snapshot-coordinates --bsk ./target/debug/bsk

Smoke alone does not certify coordinate accuracy; CLI observations do not expose raw boxes. Use the geometric test above for the regression's numeric assertions.

Separate existing boundary

The OOPIF root uses non-occupying scrollbars in the unit-conversion regression. Root and same-process frames retain normal scrollbars. Append &classic-scrollbars to the fixture URL to reproduce the separate existing OOPIF projection issue: targetProjection() maps the CSS layout viewport (which excludes occupying scrollbars) onto the entire owner content quad. This inflates the projected coordinates when scrollbars occupy space. Main already has that mapping; fixing it also changes shared live geometry and is outside this snapshot-unit fix. The test does not relax its numeric tolerance to absorb that error.