FAILURE MAP
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FA-80651 / Bidirectional text layout / Open access

Caret visual position: character direction test · case 01

Carets next to characters at level 2 are placed as if RTL.

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

ROOT CAUSE

Direction is taken as level > 0 instead of odd level.

VERIFIED REPAIR

A character is RTL only at odd levels.

Unsuccessful approach: Using the first character's level ignores the character's own direction.

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.

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, k, affinity = x
    n = len(levels)
    if n == 0:
        return 0
    vis = reorder(levels)
    pos = [0] * n
    for v, i in enumerate(vis):
        pos[i] = v
    if affinity == 'after' and k < n or k == 0:
        j = k
        leading = True
    else:
        j = k - 1
        leading = False
    rtl = levels[j] > 0
    if leading:
        return pos[j] + 1 if rtl else pos[j]
    return pos[j] if rtl else pos[j] + 1
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: character direction test', [[3, 2, 2, 2, 1, 1, 3, 3, 3], 1, 'after'], 6), ('regression: character direction test', [[1, 3, 3, 3, 3, 2, 2], 5, 'after'], 4), ('partial-repair probe', [[4, 4, 4, 4, 3, 3], 4, 'after'], 2), ('partial-repair probe', [[0, 0, 0, 0, 0, 0, 0, 0, 0, 1], 10, 'after'], 9), ('line start before', [[1, 1, 0], 0, 'before'], 2), ('line end', [[1, 1, 1], 3, 'after'], 0), ('control layout', [[1, 1, 2, 2, 1, 1, 1], 2, 'before'], 5), ('control layout', [[1, 2, 2, 2, 2, 1], 6, 'after'], 0)], [('regression: character direction test', [[1, 3, 3, 3, 3, 2, 2], 5, 'after'], 4), ('regression: character direction test', [[4, 4], 2, 'before'], 2), ('partial-repair probe', [[1, 3, 3, 3, 3, 1, 0, 0], 7, 'after'], 7), ('regression: character direction test', [[1, 1, 4, 4, 4, 4, 2], 5, 'before'], 3), ('caret at direction boundary', [[0, 0, 1, 1], 2, 'before'], 2), ('line end', [[1, 1, 1], 3, 'after'], 0), ('control layout', [[3, 2, 2, 3, 3, 3, 3], 6, 'after'], 4), ('control layout', [[3, 3, 3, 0, 2], 3, 'before'], 0)], [('regression: character direction test', [[2, 1, 1, 4, 4, 4, 4, 2, 2, 2], 5, 'before'], 2), ('regression: character direction test', [[2, 2, 2], 2, 'after'], 2), ('partial-repair probe', [[1, 0, 0, 0, 0], 3, 'after'], 3), ('partial-repair probe', [[1, 0, 1, 1, 0, 0, 0, 0, 0, 0], 7, 'after'], 7), ('same boundary after', [[0, 0, 1, 1], 2, 'after'], 4), ('line end', [[1, 1, 1], 3, 'after'], 0), ('control layout', [[0, 0, 0, 0, 0, 0, 0, 0, 0, 0], 0, 'before'], 0), ('control layout', [[3, 1, 1, 1, 1, 1, 1], 6, 'after'], 1)], [('regression: character direction test', [[2, 2, 2, 2, 2, 1, 1], 1, 'after'], 3), ('regression: character direction test', [[2, 2, 2, 2, 2, 2, 2, 1, 1], 1, 'after'], 3), ('partial-repair probe', [[4, 3], 1, 'after'], 1), ('partial-repair probe', [[0, 1, 1, 1, 1, 1, 1], 2, 'before'], 6), ('same boundary after', [[0, 0, 1, 1], 2, 'after'], 4), ('line start before', [[1, 1, 0], 0, 'before'], 2), ('control layout', [[1, 1, 1, 1, 0, 0, 0, 0, 0, 2], 2, 'after'], 2), ('control layout', [[1, 1, 1, 0, 0, 0, 0, 1], 1, 'after'], 2)], [('regression: character direction test', [[1, 2, 2, 2, 2], 2, 'before'], 1), ('regression: character direction test', [[4, 1, 4, 4], 1, 'before'], 4), ('partial-repair probe', [[3, 0, 0, 0, 2, 2, 2], 3, 'after'], 3), ('partial-repair probe', [[3, 0, 2, 2, 2], 2, 'before'], 2), ('same boundary after', [[0, 0, 1, 1], 2, 'after'], 4), ('line end', [[1, 1, 1], 3, 'after'], 0), ('control layout', [[3, 3, 1, 1, 1, 1, 1, 0, 1], 3, 'after'], 4), ('control layout', [[1, 1, 1, 1], 0, 'after'], 4)]]
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
regression: character direction test76Failed
regression: character direction test54Failed
partial-repair probe22Passed
partial-repair probe99Passed
line start before22Passed
line end00Passed
control layout55Passed
control layout00Passed

SHA-256 / 23f9692c95ed8ca7dd571310b7f5319634ad0b471718246bcd8d9c51e5d04e35

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, k, affinity = x
    n = len(levels)
    if n == 0:
        return 0
    vis = reorder(levels)
    pos = [0] * n
    for v, i in enumerate(vis):
        pos[i] = v
    if affinity == 'after' and k < n or k == 0:
        j = k
        leading = True
    else:
        j = k - 1
        leading = False
    rtl = levels[0] % 2 == 1
    if leading:
        return pos[j] + 1 if rtl else pos[j]
    return pos[j] if rtl else pos[j] + 1
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: character direction test', [[3, 2, 2, 2, 1, 1, 3, 3, 3], 1, 'after'], 6), ('regression: character direction test', [[1, 3, 3, 3, 3, 2, 2], 5, 'after'], 4), ('partial-repair probe', [[4, 4, 4, 4, 3, 3], 4, 'after'], 2), ('partial-repair probe', [[0, 0, 0, 0, 0, 0, 0, 0, 0, 1], 10, 'after'], 9), ('line start before', [[1, 1, 0], 0, 'before'], 2), ('line end', [[1, 1, 1], 3, 'after'], 0), ('control layout', [[1, 1, 2, 2, 1, 1, 1], 2, 'before'], 5), ('control layout', [[1, 2, 2, 2, 2, 1], 6, 'after'], 0)], [('regression: character direction test', [[1, 3, 3, 3, 3, 2, 2], 5, 'after'], 4), ('regression: character direction test', [[4, 4], 2, 'before'], 2), ('partial-repair probe', [[1, 3, 3, 3, 3, 1, 0, 0], 7, 'after'], 7), ('regression: character direction test', [[1, 1, 4, 4, 4, 4, 2], 5, 'before'], 3), ('caret at direction boundary', [[0, 0, 1, 1], 2, 'before'], 2), ('line end', [[1, 1, 1], 3, 'after'], 0), ('control layout', [[3, 2, 2, 3, 3, 3, 3], 6, 'after'], 4), ('control layout', [[3, 3, 3, 0, 2], 3, 'before'], 0)], [('regression: character direction test', [[2, 1, 1, 4, 4, 4, 4, 2, 2, 2], 5, 'before'], 2), ('regression: character direction test', [[2, 2, 2], 2, 'after'], 2), ('partial-repair probe', [[1, 0, 0, 0, 0], 3, 'after'], 3), ('partial-repair probe', [[1, 0, 1, 1, 0, 0, 0, 0, 0, 0], 7, 'after'], 7), ('same boundary after', [[0, 0, 1, 1], 2, 'after'], 4), ('line end', [[1, 1, 1], 3, 'after'], 0), ('control layout', [[0, 0, 0, 0, 0, 0, 0, 0, 0, 0], 0, 'before'], 0), ('control layout', [[3, 1, 1, 1, 1, 1, 1], 6, 'after'], 1)], [('regression: character direction test', [[2, 2, 2, 2, 2, 1, 1], 1, 'after'], 3), ('regression: character direction test', [[2, 2, 2, 2, 2, 2, 2, 1, 1], 1, 'after'], 3), ('partial-repair probe', [[4, 3], 1, 'after'], 1), ('partial-repair probe', [[0, 1, 1, 1, 1, 1, 1], 2, 'before'], 6), ('same boundary after', [[0, 0, 1, 1], 2, 'after'], 4), ('line start before', [[1, 1, 0], 0, 'before'], 2), ('control layout', [[1, 1, 1, 1, 0, 0, 0, 0, 0, 2], 2, 'after'], 2), ('control layout', [[1, 1, 1, 0, 0, 0, 0, 1], 1, 'after'], 2)], [('regression: character direction test', [[1, 2, 2, 2, 2], 2, 'before'], 1), ('regression: character direction test', [[4, 1, 4, 4], 1, 'before'], 4), ('partial-repair probe', [[3, 0, 0, 0, 2, 2, 2], 3, 'after'], 3), ('partial-repair probe', [[3, 0, 2, 2, 2], 2, 'before'], 2), ('same boundary after', [[0, 0, 1, 1], 2, 'after'], 4), ('line end', [[1, 1, 1], 3, 'after'], 0), ('control layout', [[3, 3, 1, 1, 1, 1, 1, 0, 1], 3, 'after'], 4), ('control layout', [[1, 1, 1, 1], 0, 'after'], 4)]]
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
regression: character direction test76Failed
regression: character direction test54Failed
partial-repair probe12Failed
partial-repair probe109Failed
line start before22Passed
line end00Passed
control layout55Passed
control layout00Passed

SHA-256 / ad27bd2bd11dd8c026d97b77b413ce9d46cdf90d188b580109b7917964527196

3 / The verified repair

Exit 0
"""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, k, affinity = x
    n = len(levels)
    if n == 0:
        return 0
    vis = reorder(levels)
    pos = [0] * n
    for v, i in enumerate(vis):
        pos[i] = v
    if affinity == 'after' and k < n or k == 0:
        j = k
        leading = True
    else:
        j = k - 1
        leading = False
    rtl = levels[j] % 2 == 1
    if leading:
        return pos[j] + 1 if rtl else pos[j]
    return pos[j] if rtl else pos[j] + 1
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: character direction test', [[3, 2, 2, 2, 1, 1, 3, 3, 3], 1, 'after'], 6), ('regression: character direction test', [[1, 3, 3, 3, 3, 2, 2], 5, 'after'], 4), ('partial-repair probe', [[4, 4, 4, 4, 3, 3], 4, 'after'], 2), ('partial-repair probe', [[0, 0, 0, 0, 0, 0, 0, 0, 0, 1], 10, 'after'], 9), ('line start before', [[1, 1, 0], 0, 'before'], 2), ('line end', [[1, 1, 1], 3, 'after'], 0), ('control layout', [[1, 1, 2, 2, 1, 1, 1], 2, 'before'], 5), ('control layout', [[1, 2, 2, 2, 2, 1], 6, 'after'], 0)], [('regression: character direction test', [[1, 3, 3, 3, 3, 2, 2], 5, 'after'], 4), ('regression: character direction test', [[4, 4], 2, 'before'], 2), ('partial-repair probe', [[1, 3, 3, 3, 3, 1, 0, 0], 7, 'after'], 7), ('regression: character direction test', [[1, 1, 4, 4, 4, 4, 2], 5, 'before'], 3), ('caret at direction boundary', [[0, 0, 1, 1], 2, 'before'], 2), ('line end', [[1, 1, 1], 3, 'after'], 0), ('control layout', [[3, 2, 2, 3, 3, 3, 3], 6, 'after'], 4), ('control layout', [[3, 3, 3, 0, 2], 3, 'before'], 0)], [('regression: character direction test', [[2, 1, 1, 4, 4, 4, 4, 2, 2, 2], 5, 'before'], 2), ('regression: character direction test', [[2, 2, 2], 2, 'after'], 2), ('partial-repair probe', [[1, 0, 0, 0, 0], 3, 'after'], 3), ('partial-repair probe', [[1, 0, 1, 1, 0, 0, 0, 0, 0, 0], 7, 'after'], 7), ('same boundary after', [[0, 0, 1, 1], 2, 'after'], 4), ('line end', [[1, 1, 1], 3, 'after'], 0), ('control layout', [[0, 0, 0, 0, 0, 0, 0, 0, 0, 0], 0, 'before'], 0), ('control layout', [[3, 1, 1, 1, 1, 1, 1], 6, 'after'], 1)], [('regression: character direction test', [[2, 2, 2, 2, 2, 1, 1], 1, 'after'], 3), ('regression: character direction test', [[2, 2, 2, 2, 2, 2, 2, 1, 1], 1, 'after'], 3), ('partial-repair probe', [[4, 3], 1, 'after'], 1), ('partial-repair probe', [[0, 1, 1, 1, 1, 1, 1], 2, 'before'], 6), ('same boundary after', [[0, 0, 1, 1], 2, 'after'], 4), ('line start before', [[1, 1, 0], 0, 'before'], 2), ('control layout', [[1, 1, 1, 1, 0, 0, 0, 0, 0, 2], 2, 'after'], 2), ('control layout', [[1, 1, 1, 0, 0, 0, 0, 1], 1, 'after'], 2)], [('regression: character direction test', [[1, 2, 2, 2, 2], 2, 'before'], 1), ('regression: character direction test', [[4, 1, 4, 4], 1, 'before'], 4), ('partial-repair probe', [[3, 0, 0, 0, 2, 2, 2], 3, 'after'], 3), ('partial-repair probe', [[3, 0, 2, 2, 2], 2, 'before'], 2), ('same boundary after', [[0, 0, 1, 1], 2, 'after'], 4), ('line end', [[1, 1, 1], 3, 'after'], 0), ('control layout', [[3, 3, 1, 1, 1, 1, 1, 0, 1], 3, 'after'], 4), ('control layout', [[1, 1, 1, 1], 0, 'after'], 4)]]
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
regression: character direction test66Passed
regression: character direction test44Passed
partial-repair probe22Passed
partial-repair probe99Passed
line start before22Passed
line end00Passed
control layout55Passed
control layout00Passed

SHA-256 / 9f213492c1194d5fea191d1acad57ee6555a7be1bfc2b0b05a1f9df34caddc8f

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 2026-09-29T14:49:55.832585+00:00.

Case digest / cfa562b5cbf9cda40acf1a91a74e0392db9cf7260820b0a268140c6a6dffb895