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FA-8361 / Keyboard accessibility / Open access

Grid-cell keyboard movement: Right arrows wrap instead of staying at the row edge · case 01

Right arrows wrap instead of staying at the row edge.

Verified by executionVariant 1 · 11 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The right clamp operation uses `(column+1) % columns` where the contract requires `min(columns-1, column+1)`.

VERIFIED REPAIR

Implement the right clamp operation as `min(columns-1, column+1)`.

Unsuccessful approach: Clamping columns against row count fails nonsquare grids.

Case contract

Arrow keys move one cell and clamp without wrapping; Home/End target row edges; Control additionally targets the first/last row.

Why this case matters

A deterministic model of grid-cell keyboard movement; this isolates one interface invariant without requiring a browser.

1 / The failure

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

N = 1
observations = []
def solve(rows, columns, row, column, key, ctrl):
    if key == 'Left': column = max(0, column-1)
    elif key == 'Right': column = (column+1) % columns
    elif key == 'Up': row = max(0, row-1)
    elif key == 'Down': row = min(rows-1, row+1)
    elif key == 'Home': column = 0; row = 0 if ctrl else row
    elif key == 'End': column = columns-1; row = rows-1 if ctrl else row
    return (row, column)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('left boundary', solve(3, 5, 1, 0, 'Left', False), (1, 0))
check('left step', solve(3, 5, 1, 3, 'Left', False), (1, 2))
check('right boundary', solve(3, 5, 1, 4, 'Right', False), (1, 4))
check('right step', solve(3, 5, 1, 3, 'Right', False), (1, 4))
check('up', solve(3, 5, 1, 3, 'Up', False), (0, 3))
check('home', solve(3, 5, 1, 3, 'Home', False), (1, 0))
check('ctrl home', solve(3, 5, 1, 3, 'Home', True), (0, 0))
check('end', solve(3, 5, 1, 3, 'End', False), (1, 4))
check('ctrl end', solve(3, 5, 1, 3, 'End', True), (2, 4))
check('parameterized grid shape', solve(N+2,N+3,N,N,'Right',False), (N,N+1))
for repetition in range(N):
    check('repeat ctrl end', solve(3, 5, 1, 3, 'End', True), (2, 4))
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
left boundary[1, 0][1, 0]Passed
left step[1, 2][1, 2]Passed
right boundary[1, 0][1, 4]Failed
right step[1, 4][1, 4]Passed
up[0, 3][0, 3]Passed
home[1, 0][1, 0]Passed
ctrl home[0, 0][0, 0]Passed
end[1, 4][1, 4]Passed
ctrl end[2, 4][2, 4]Passed
parameterized grid shape[1, 2][1, 2]Passed
repeat ctrl end[2, 4][2, 4]Passed

SHA-256 / 18d3ed069320510f31fe02da66e8d285b99fe7ba24f52ee13c5decb9b1847105

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(rows, columns, row, column, key, ctrl):
    if key == 'Left': column = max(0, column-1)
    elif key == 'Right': column = min(rows-1, column+1)
    elif key == 'Up': row = max(0, row-1)
    elif key == 'Down': row = min(rows-1, row+1)
    elif key == 'Home': column = 0; row = 0 if ctrl else row
    elif key == 'End': column = columns-1; row = rows-1 if ctrl else row
    return (row, column)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('left boundary', solve(3, 5, 1, 0, 'Left', False), (1, 0))
check('left step', solve(3, 5, 1, 3, 'Left', False), (1, 2))
check('right boundary', solve(3, 5, 1, 4, 'Right', False), (1, 4))
check('right step', solve(3, 5, 1, 3, 'Right', False), (1, 4))
check('up', solve(3, 5, 1, 3, 'Up', False), (0, 3))
check('home', solve(3, 5, 1, 3, 'Home', False), (1, 0))
check('ctrl home', solve(3, 5, 1, 3, 'Home', True), (0, 0))
check('end', solve(3, 5, 1, 3, 'End', False), (1, 4))
check('ctrl end', solve(3, 5, 1, 3, 'End', True), (2, 4))
check('parameterized grid shape', solve(N+2,N+3,N,N,'Right',False), (N,N+1))
for repetition in range(N):
    check('repeat ctrl end', solve(3, 5, 1, 3, 'End', True), (2, 4))
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
left boundary[1, 0][1, 0]Passed
left step[1, 2][1, 2]Passed
right boundary[1, 2][1, 4]Failed
right step[1, 2][1, 4]Failed
up[0, 3][0, 3]Passed
home[1, 0][1, 0]Passed
ctrl home[0, 0][0, 0]Passed
end[1, 4][1, 4]Passed
ctrl end[2, 4][2, 4]Passed
parameterized grid shape[1, 2][1, 2]Passed
repeat ctrl end[2, 4][2, 4]Passed

SHA-256 / d94e2c16bfd08838d8da329eed765028098886a3378da1442b2654c4a308aa91

3 / The verified repair

Exit 0
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(rows, columns, row, column, key, ctrl):
    if key == 'Left': column = max(0, column-1)
    elif key == 'Right': column = min(columns-1, column+1)
    elif key == 'Up': row = max(0, row-1)
    elif key == 'Down': row = min(rows-1, row+1)
    elif key == 'Home': column = 0; row = 0 if ctrl else row
    elif key == 'End': column = columns-1; row = rows-1 if ctrl else row
    return (row, column)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('left boundary', solve(3, 5, 1, 0, 'Left', False), (1, 0))
check('left step', solve(3, 5, 1, 3, 'Left', False), (1, 2))
check('right boundary', solve(3, 5, 1, 4, 'Right', False), (1, 4))
check('right step', solve(3, 5, 1, 3, 'Right', False), (1, 4))
check('up', solve(3, 5, 1, 3, 'Up', False), (0, 3))
check('home', solve(3, 5, 1, 3, 'Home', False), (1, 0))
check('ctrl home', solve(3, 5, 1, 3, 'Home', True), (0, 0))
check('end', solve(3, 5, 1, 3, 'End', False), (1, 4))
check('ctrl end', solve(3, 5, 1, 3, 'End', True), (2, 4))
check('parameterized grid shape', solve(N+2,N+3,N,N,'Right',False), (N,N+1))
for repetition in range(N):
    check('repeat ctrl end', solve(3, 5, 1, 3, 'End', True), (2, 4))
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
left boundary[1, 0][1, 0]Passed
left step[1, 2][1, 2]Passed
right boundary[1, 4][1, 4]Passed
right step[1, 4][1, 4]Passed
up[0, 3][0, 3]Passed
home[1, 0][1, 0]Passed
ctrl home[0, 0][0, 0]Passed
end[1, 4][1, 4]Passed
ctrl end[2, 4][2, 4]Passed
parameterized grid shape[1, 2][1, 2]Passed
repeat ctrl end[2, 4][2, 4]Passed

SHA-256 / 08124ba6b65cc3f2bd3bca53c5632ac0f44721143cf2998bf0c58251541957cb

Verification & scope

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 2026-09-29T14:38:20.778708+00:00.

Case digest / 7c92064a611bac53e3d9319ee99177a16017f2b5e4b9a8e2318bb8189fed4db9