FA-80659 / Bidirectional text layout / Member archive

Caret visual position: line start caret · case 04

A caret at offset 0 with backward affinity lands at the end of the line.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

Input [levels, logical caret offset k, affinity]. Characters are one unit wide and visually ordered by level reversal. Affinity "after" attaches the caret to the leading edge of character k (if k < n), otherwise to the trailing edge of character k-1; offset 0 always uses the leading edge of character 0. The leading edge of an LTR character is its left side, of an RTL (odd) character its right side. Return the visual x.

Why this case matters

Mixed right-to-left and left-to-right text must resolve levels and visual order exactly, or words, numbers and carets land in the wrong place.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
regression: line start caret	`0`	`3`	Failed

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This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

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