FA-80800 / Bidirectional text layout / Member archive

Visual run list for shaping: run direction label · case 05

Level-2 runs are shaped right-to-left.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

Input resolved levels of a line. Group maximal equal-level runs [logical start, length, level]; reorder whole runs from the highest level down to the lowest odd level by reversing sequences of runs at or above the level. Return [[start, length, "rtl"|"ltr"]] in visual order.

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: run direction label	`[[4, 1, "rtl"], [0, 4, "rtl"]]`	`[[4, 1, "rtl"], [0, 4, "ltr"]]`	Failed

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