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FA-80666 / Bidirectional text layout / Open access

Bidi selection highlight: slot sorting · case 01

RTL selections are drawn as many one-unit fragments.

Verified by executionVariant 1 · 8 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Visual slots are merged in logical order without sorting.

THE FAILURE

Visual slots are merged in logical order without sorting.

Unsuccessful approach: Sorting in descending order defeats the adjacency merge.

Case contract

Input [levels, anchor, focus]. The logical selection covers characters min..max-1. Each selected character occupies its unit visual slot (level reversal); merge adjacent slots into [x0, x1) rectangles sorted by x. Return the rectangles.

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.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(x):
    def reorder(lv):
        vis = list(range(len(lv)))
        odd = [l for l in lv if l % 2 == 1]
        if not odd:
            return vis
        for lev in range(max(lv), min(odd) - 1, -1):
            i = 0
            while i < len(vis):
                if lv[vis[i]] >= lev:
                    j = i
                    while j < len(vis) and lv[vis[j]] >= lev:
                        j += 1
                    vis[i:j] = vis[i:j][::-1]
                    i = j
                else:
                    i += 1
        return vis
    
    levels, a, b = x
    a, b = min(a, b), max(a, b)
    vis = reorder(levels)
    pos = [0] * len(levels)
    for v, i in enumerate(vis):
        pos[i] = v
    sel = [pos[i] for i in range(a, b)]
    rects = []
    for p in sel:
        if rects and rects[-1][1] == p:
            rects[-1][1] = p + 1
        else:
            rects.append([p, p + 1])
    return rects
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('selection crossing direction change', [[0, 0, 1, 1, 0], 1, 4], [[1, 4]]), ('regression: slot sorting', [[0, 0, 0, 0, 2, 0, 0, 0, 3, 3, 0, 0], 12, 7], [[7, 12]]), ('partial-repair probe', [[0, 0, 0, 0, 0, 2, 0, 0, 1, 0], 8, 6], [[6, 8]]), ('partial-repair probe', [[2, 2, 2, 2, 1, 1, 4, 4, 4, 4, 1], 8, 6], [[1, 3]]), ('backward selection', [[1, 1, 1], 3, 1], [[0, 2]]), ('control layout', [[4, 4, 4, 4, 1, 1, 3], 1, 0], [[3, 4]]), ('control layout', [[2, 2, 2, 1, 1, 1, 1, 3, 3], 6, 5], [[3, 4]]), ('control layout', [[0], 1, 1], [])], [('regression: slot sorting', [[3, 3, 3, 3, 3, 3, 3, 2], 8, 4], [[0, 3], [7, 8]]), ('regression: slot sorting', [[1, 1, 1, 1, 3, 1, 1, 1, 2, 2, 2], 9, 3], [[0, 1], [3, 8]]), ('regression: slot sorting', [[3, 3, 3, 1, 1, 1, 2], 4, 2], [[3, 5]]), ('regression: slot sorting', [[3, 3, 3, 2, 2, 1, 1, 1, 1, 2, 2], 3, 8], [[3, 6], [9, 11]]), ('selection crossing direction change', [[0, 0, 1, 1, 0], 1, 4], [[1, 4]]), ('backward selection', [[1, 1, 1], 3, 1], [[0, 2]]), ('control layout', [[1, 2, 2, 2, 4, 4, 4, 4, 1, 1, 1], 10, 9], [[1, 2]]), ('control layout', [[1, 1, 2, 2, 2, 2, 1, 3, 3, 1, 1], 8, 9], [[2, 3]])], [('backward selection', [[1, 1, 1], 3, 1], [[0, 2]]), ('regression: slot sorting', [[1, 1, 1, 1, 4, 4, 3, 2, 2], 4, 7], [[0, 3]]), ('regression: slot sorting', [[1, 1, 1, 4, 4, 3, 3, 3, 2], 3, 7], [[1, 5]]), ('partial-repair probe', [[0, 0, 0, 0, 0, 2, 0, 0, 1, 0], 8, 6], [[6, 8]]), ('selection crossing direction change', [[0, 0, 1, 1, 0], 1, 4], [[1, 4]]), ('control layout', [[0, 0], 0, 0], []), ('control layout', [[3, 3, 3, 1, 1, 1, 1, 2, 2, 2, 2], 2, 1], [[9, 10]]), ('control layout', [[1, 1], 1, 1], [])], [('regression: slot sorting', [[4, 4, 4, 1, 1, 1, 1, 1, 1, 1, 1], 6, 11], [[0, 5]]), ('regression: slot sorting', [[1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 3], 8, 3], [[4, 9]]), ('regression: slot sorting', [[3, 3, 3, 3, 2], 4, 2], [[0, 2]]), ('partial-repair probe', [[4, 2, 2, 2, 2, 2, 2, 2], 7, 1], [[1, 7]]), ('backward selection', [[1, 1, 1], 3, 1], [[0, 2]]), ('selection crossing direction change', [[0, 0, 1, 1, 0], 1, 4], [[1, 4]]), ('control layout', [[2, 2], 0, 0], []), ('control layout', [[1, 3, 3, 3, 3, 0, 0], 1, 0], [[4, 5]])], [('regression: slot sorting', [[0, 1, 1, 2, 2, 0, 0, 0, 0], 2, 8], [[1, 4], [5, 8]]), ('regression: slot sorting', [[2, 2, 1, 1], 4, 1], [[0, 2], [3, 4]]), ('regression: slot sorting', [[1, 1, 1, 4, 4, 4], 3, 1], [[3, 5]]), ('partial-repair probe', [[2, 2, 4, 2, 2, 2, 2, 2], 7, 4], [[4, 7]]), ('selection crossing direction change', [[0, 0, 1, 1, 0], 1, 4], [[1, 4]]), ('backward selection', [[1, 1, 1], 3, 1], [[0, 2]]), ('control layout', [[1, 3, 3, 3, 0, 0, 3, 3], 8, 8], []), ('control layout', [[2, 2, 2, 2, 2, 4, 4, 4, 3, 3, 3], 10, 11], [[5, 6]])]]
for label, args, expected in fixtures[N - 1]:
    check(label, solve(args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
selection crossing direction change[[1, 2], [3, 4], [2, 3]][[1, 4]]Failed
regression: slot sorting[[7, 8], [9, 10], [8, 9], [10, 12]][[7, 12]]Failed
partial-repair probe[[6, 8]][[6, 8]]Passed
partial-repair probe[[1, 3]][[1, 3]]Passed
backward selection[[1, 2], [0, 1]][[0, 2]]Failed
control layout[[3, 4]][[3, 4]]Passed
control layout[[3, 4]][[3, 4]]Passed
control layout[][]Passed

SHA-256 / 8ca99e755671cbb5e3edb762933f7699af3ba0db5f8b243aa0b7aeb6e7b80d96

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(x):
    def reorder(lv):
        vis = list(range(len(lv)))
        odd = [l for l in lv if l % 2 == 1]
        if not odd:
            return vis
        for lev in range(max(lv), min(odd) - 1, -1):
            i = 0
            while i < len(vis):
                if lv[vis[i]] >= lev:
                    j = i
                    while j < len(vis) and lv[vis[j]] >= lev:
                        j += 1
                    vis[i:j] = vis[i:j][::-1]
                    i = j
                else:
                    i += 1
        return vis
    
    levels, a, b = x
    a, b = min(a, b), max(a, b)
    vis = reorder(levels)
    pos = [0] * len(levels)
    for v, i in enumerate(vis):
        pos[i] = v
    sel = sorted((pos[i] for i in range(a, b)), reverse=True)
    rects = []
    for p in sel:
        if rects and rects[-1][1] == p:
            rects[-1][1] = p + 1
        else:
            rects.append([p, p + 1])
    return rects
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('selection crossing direction change', [[0, 0, 1, 1, 0], 1, 4], [[1, 4]]), ('regression: slot sorting', [[0, 0, 0, 0, 2, 0, 0, 0, 3, 3, 0, 0], 12, 7], [[7, 12]]), ('partial-repair probe', [[0, 0, 0, 0, 0, 2, 0, 0, 1, 0], 8, 6], [[6, 8]]), ('partial-repair probe', [[2, 2, 2, 2, 1, 1, 4, 4, 4, 4, 1], 8, 6], [[1, 3]]), ('backward selection', [[1, 1, 1], 3, 1], [[0, 2]]), ('control layout', [[4, 4, 4, 4, 1, 1, 3], 1, 0], [[3, 4]]), ('control layout', [[2, 2, 2, 1, 1, 1, 1, 3, 3], 6, 5], [[3, 4]]), ('control layout', [[0], 1, 1], [])], [('regression: slot sorting', [[3, 3, 3, 3, 3, 3, 3, 2], 8, 4], [[0, 3], [7, 8]]), ('regression: slot sorting', [[1, 1, 1, 1, 3, 1, 1, 1, 2, 2, 2], 9, 3], [[0, 1], [3, 8]]), ('regression: slot sorting', [[3, 3, 3, 1, 1, 1, 2], 4, 2], [[3, 5]]), ('regression: slot sorting', [[3, 3, 3, 2, 2, 1, 1, 1, 1, 2, 2], 3, 8], [[3, 6], [9, 11]]), ('selection crossing direction change', [[0, 0, 1, 1, 0], 1, 4], [[1, 4]]), ('backward selection', [[1, 1, 1], 3, 1], [[0, 2]]), ('control layout', [[1, 2, 2, 2, 4, 4, 4, 4, 1, 1, 1], 10, 9], [[1, 2]]), ('control layout', [[1, 1, 2, 2, 2, 2, 1, 3, 3, 1, 1], 8, 9], [[2, 3]])], [('backward selection', [[1, 1, 1], 3, 1], [[0, 2]]), ('regression: slot sorting', [[1, 1, 1, 1, 4, 4, 3, 2, 2], 4, 7], [[0, 3]]), ('regression: slot sorting', [[1, 1, 1, 4, 4, 3, 3, 3, 2], 3, 7], [[1, 5]]), ('partial-repair probe', [[0, 0, 0, 0, 0, 2, 0, 0, 1, 0], 8, 6], [[6, 8]]), ('selection crossing direction change', [[0, 0, 1, 1, 0], 1, 4], [[1, 4]]), ('control layout', [[0, 0], 0, 0], []), ('control layout', [[3, 3, 3, 1, 1, 1, 1, 2, 2, 2, 2], 2, 1], [[9, 10]]), ('control layout', [[1, 1], 1, 1], [])], [('regression: slot sorting', [[4, 4, 4, 1, 1, 1, 1, 1, 1, 1, 1], 6, 11], [[0, 5]]), ('regression: slot sorting', [[1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 3], 8, 3], [[4, 9]]), ('regression: slot sorting', [[3, 3, 3, 3, 2], 4, 2], [[0, 2]]), ('partial-repair probe', [[4, 2, 2, 2, 2, 2, 2, 2], 7, 1], [[1, 7]]), ('backward selection', [[1, 1, 1], 3, 1], [[0, 2]]), ('selection crossing direction change', [[0, 0, 1, 1, 0], 1, 4], [[1, 4]]), ('control layout', [[2, 2], 0, 0], []), ('control layout', [[1, 3, 3, 3, 3, 0, 0], 1, 0], [[4, 5]])], [('regression: slot sorting', [[0, 1, 1, 2, 2, 0, 0, 0, 0], 2, 8], [[1, 4], [5, 8]]), ('regression: slot sorting', [[2, 2, 1, 1], 4, 1], [[0, 2], [3, 4]]), ('regression: slot sorting', [[1, 1, 1, 4, 4, 4], 3, 1], [[3, 5]]), ('partial-repair probe', [[2, 2, 4, 2, 2, 2, 2, 2], 7, 4], [[4, 7]]), ('selection crossing direction change', [[0, 0, 1, 1, 0], 1, 4], [[1, 4]]), ('backward selection', [[1, 1, 1], 3, 1], [[0, 2]]), ('control layout', [[1, 3, 3, 3, 0, 0, 3, 3], 8, 8], []), ('control layout', [[2, 2, 2, 2, 2, 4, 4, 4, 3, 3, 3], 10, 11], [[5, 6]])]]
for label, args, expected in fixtures[N - 1]:
    check(label, solve(args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
selection crossing direction change[[3, 4], [2, 3], [1, 2]][[1, 4]]Failed
regression: slot sorting[[11, 12], [10, 11], [9, 10], [8, 9], [7, 8]][[7, 12]]Failed
partial-repair probe[[7, 8], [6, 7]][[6, 8]]Failed
partial-repair probe[[2, 3], [1, 2]][[1, 3]]Failed
backward selection[[1, 2], [0, 1]][[0, 2]]Failed
control layout[[3, 4]][[3, 4]]Passed
control layout[[3, 4]][[3, 4]]Passed
control layout[][]Passed

SHA-256 / 17f8ab11d760b234fc48fc076a9ec7c43baadabb29b6344544c6c333333fffcd

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 8 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.

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Verification & scope

A deterministic toy bidi model over stipulated class labels and integer levels; it is inspired by, but does not claim conformance to, any published algorithm. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:49:56.106345+00:00.

Case digest / 6365b6d9ae91c6444ee56eb6a7aeccae2da0bbc794957f685dcd68d8d401b9b6