FA-80527 / Bidirectional text layout / Member archive

Explicit embedding stack: next even level · case 02

LRE inside an RTL embedding skips a level.

Member previewVariant 2 · 3 implementations · 8 checks per implementation

Case contract

Input [classes, paragraph level, max depth]. RLE/RLO push the next odd level, LRE/LRO the next even level (RLO/LRO set an R/L override, RLE/LRE clear it) if the level <= max depth and no overflow is pending, else count an overflow. PDF first cancels an overflow, else pops if above the base. Codes get level "x" and class BN; other characters take the top level and the override class if any. Return [levels, classes].

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: next even level	`[[1, "x", "x", "x", "x", 5, 5, "x", 5, 5, "x", 5], ["WS", "BN", "BN", "BN", "BN", "R", "R", "BN", "R", "R", "BN", "R"]]`	`[[1, "x", "x", "x", "x", 4, 4, "x", 4, 4, "x", 4], ["WS", "BN", "BN", "BN", "BN", "L", "L", "BN", "L", "L", "BN", "L"]]`	Failed

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