FA-54115 / Accessibility interaction semantics / Member archive

Selection API accepts a negative anchor · case 05

Selection API accepts a negative anchor.

Member previewVariant 5 · 3 implementations · 9 checks per implementation

Case contract

Input [text_length,multi,readonly,selections,operation] selections ordered [anchor,focus]; operation [kind,index,anchor,focus]. API supports add,replace,remove,clear; readonly concerns text edits and does not prevent selecting. Validate endpoints inclusive0..length and index for replace/remove. add only when multi or no selection; remove preserves other ranges; clear ignores index. Return [ranges,success,active] where active is last range's focus or None. Preserve anchor direction and collapsed selections. Failure leaves input unchanged.

Why this case matters

Offline accessibility bridge model with explicit policy; useful for testing semantic API adapters independently of browser implementations.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
contract fixture 8	`[[[-1, 3]], true, 3]`	`[[], false, null]`	Failed

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