{"abstract":"Clicks hit the character with the logical index equal to the slot.","category":"Bidirectional text layout","checks":8,"contract":"Input [levels, x in half-character units]. Clamp to a visual slot (each character 2 units). The right half of an LTR character or the left half of an RTL character is its trailing side. Points before the line use the left half of slot 0, beyond it the right half of the last slot. Return [logical index, trailing, caret offset].","evaluation_group":"w2-bidirectional-text-layout-hit-testing","failed_approach":"Reading the order backwards is not the mapping either.","family":"w2-bidirectional-text-layout-hit-testing-visual-slot-lookup","id":"FA-80696","implementations":{"attempt":{"sha256":"1ae877f596255b6be4a04c0629543a7c808a708245d35bb6e4477e5979424865","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x):\n    def reorder(lv):\n        vis = list(range(len(lv)))\n        odd = [l for l in lv if l % 2 == 1]\n        if not odd:\n            return vis\n        for lev in range(max(lv), min(odd) - 1, -1):\n            i = 0\n            while i < len(vis):\n                if lv[vis[i]] >= lev:\n                    j = i\n                    while j < len(vis) and lv[vis[j]] >= lev:\n                        j += 1\n                    vis[i:j] = vis[i:j][::-1]\n                    i = j\n                else:\n                    i += 1\n        return vis\n    \n    levels, px = x\n    n = len(levels)\n    if n == 0:\n        return [None, False, 0]\n    vis = reorder(levels)\n    v = min(max(px // 2, 0), n - 1)\n    i = vis[n - 1 - v]\n    right_half = px - 2 * v >= 1\n    rtl = levels[i] % 2 == 1\n    trailing = right_half != rtl\n    return [i, trailing, i + 1 if trailing else i]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[('click left of RTL line', [[1, 1, 1], -1], [2, True, 3]), ('regression: visual slot lookup', [[2, 2, 2, 1, 1], 8], [2, False, 2]), ('regression: visual slot lookup', [[1, 1, 1, 1, 3, 3, 0, 1, 2, 2], 1], [5, False, 5]), ('partial-repair probe', [[0, 0, 0, 0], -1], [0, False, 0]), ('click past end', [[0, 1, 1], 9], [1, False, 1]), ('right half of RTL char', [[1, 1], 1], [1, False, 1]), ('control layout', [[1], 4], [0, False, 0]), ('control layout', [[2, 2, 2, 2, 2, 4, 2, 2, 2], 9], [4, True, 5])], [('regression: visual slot lookup', [[1, 1, 1, 3], 10], [0, False, 0]), ('regression: visual slot lookup', [[1, 1, 1, 1, 1, 1], 9], [1, False, 1]), ('regression: visual slot lookup', [[1, 1, 1, 0, 0, 1, 1], -3], [2, True, 3]), ('regression: visual slot lookup', [[1, 1, 2, 2, 2, 3, 3], 16], [0, False, 0]), ('right half of RTL char', [[1, 1], 1], [1, False, 1]), ('click past end', [[0, 1, 1], 9], [1, False, 1]), ('control layout', [[1], 4], [0, False, 0]), ('control layout', [[4, 4, 4, 1, 4, 4, 4], 6], [3, True, 4])], [('regression: visual slot lookup', [[3, 3, 3, 3, 3, 1, 2, 2, 2, 2], 11], [4, False, 4]), ('regression: visual slot lookup', [[1, 2], 7], [0, False, 0]), ('regression: visual slot lookup', [[4, 4, 4, 4, 1, 1], 11], [3, True, 4]), ('regression: visual slot lookup', [[2, 2, 2, 1, 1, 1, 2], 0], [6, False, 6]), ('click past end', [[0, 1, 1], 9], [1, False, 1]), ('click left of RTL line', [[1, 1, 1], -1], [2, True, 3]), ('control layout', [[2], 4], [0, True, 1]), ('control layout', [[1], 3], [0, False, 0])], [('regression: visual slot lookup', [[1, 3, 3, 3, 3, 1, 1, 1], 9], [3, False, 3]), ('regression: visual slot lookup', [[1, 1, 1, 0, 0, 0, 3], -1], [2, True, 3]), ('partial-repair probe', [[1, 0, 0, 0, 0], -1], [0, True, 1]), ('regression: visual slot lookup', [[1, 1, 1, 1, 1, 1, 1, 1, 3], 17], [0, False, 0]), ('click left of RTL line', [[1, 1, 1], -1], [2, True, 3]), ('click past end', [[0, 1, 1], 9], [1, False, 1]), ('control layout', [[1], 3], [0, False, 0]), ('control layout', [[1], -2], [0, True, 1])], [('regression: visual slot lookup', [[3, 3, 0, 0, 0], -2], [1, True, 2]), ('regression: visual slot lookup', [[1, 1, 1, 3, 3], 13], [0, False, 0]), ('regression: visual slot lookup', [[3, 3, 3, 3, 1, 1, 1], -2], [6, True, 7]), ('regression: visual slot lookup', [[0, 0, 0, 2, 2, 3, 3, 3, 3, 1], 20], [5, False, 5]), ('click past end', [[0, 1, 1], 9], [1, False, 1]), ('right half of RTL char', [[1, 1], 1], [1, False, 1]), ('control layout', [[1], 0], [0, True, 1]), ('control layout', [[2, 2, 2], 3], [1, True, 2])]]\nfor label, args, expected in fixtures[N - 1]:\n    check(label, solve(args), expected)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"broken":{"sha256":"fac5fdf7c5b358961ddccdfa6c5c4c8ff3b97c9854cae4f4cf639d42726bc498","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x):\n    def reorder(lv):\n        vis = list(range(len(lv)))\n        odd = [l for l in lv if l % 2 == 1]\n        if not odd:\n            return vis\n        for lev in range(max(lv), min(odd) - 1, -1):\n            i = 0\n            while i < len(vis):\n                if lv[vis[i]] >= lev:\n                    j = i\n                    while j < len(vis) and lv[vis[j]] >= lev:\n                        j += 1\n                    vis[i:j] = vis[i:j][::-1]\n                    i = j\n                else:\n                    i += 1\n        return vis\n    \n    levels, px = x\n    n = len(levels)\n    if n == 0:\n        return [None, False, 0]\n    vis = reorder(levels)\n    v = min(max(px // 2, 0), n - 1)\n    i = v\n    right_half = px - 2 * v >= 1\n    rtl = levels[i] % 2 == 1\n    trailing = right_half != rtl\n    return [i, trailing, i + 1 if trailing else i]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[('click left of RTL line', [[1, 1, 1], -1], [2, True, 3]), ('regression: visual slot lookup', [[2, 2, 2, 1, 1], 8], [2, False, 2]), ('regression: visual slot lookup', [[1, 1, 1, 1, 3, 3, 0, 1, 2, 2], 1], [5, False, 5]), ('partial-repair probe', [[0, 0, 0, 0], -1], [0, False, 0]), ('click past end', [[0, 1, 1], 9], [1, False, 1]), ('right half of RTL char', [[1, 1], 1], [1, False, 1]), ('control layout', [[1], 4], [0, False, 0]), ('control layout', [[2, 2, 2, 2, 2, 4, 2, 2, 2], 9], [4, True, 5])], [('regression: visual slot lookup', [[1, 1, 1, 3], 10], [0, False, 0]), ('regression: visual slot lookup', [[1, 1, 1, 1, 1, 1], 9], [1, False, 1]), ('regression: visual slot lookup', [[1, 1, 1, 0, 0, 1, 1], -3], [2, True, 3]), ('regression: visual slot lookup', [[1, 1, 2, 2, 2, 3, 3], 16], [0, False, 0]), ('right half of RTL char', [[1, 1], 1], [1, False, 1]), ('click past end', [[0, 1, 1], 9], [1, False, 1]), ('control layout', [[1], 4], [0, False, 0]), ('control layout', [[4, 4, 4, 1, 4, 4, 4], 6], [3, True, 4])], [('regression: visual slot lookup', [[3, 3, 3, 3, 3, 1, 2, 2, 2, 2], 11], [4, False, 4]), ('regression: visual slot lookup', [[1, 2], 7], [0, False, 0]), ('regression: visual slot lookup', [[4, 4, 4, 4, 1, 1], 11], [3, True, 4]), ('regression: visual slot lookup', [[2, 2, 2, 1, 1, 1, 2], 0], [6, False, 6]), ('click past end', [[0, 1, 1], 9], [1, False, 1]), ('click left of RTL line', [[1, 1, 1], -1], [2, True, 3]), ('control layout', [[2], 4], [0, True, 1]), ('control layout', [[1], 3], [0, False, 0])], [('regression: visual slot lookup', [[1, 3, 3, 3, 3, 1, 1, 1], 9], [3, False, 3]), ('regression: visual slot lookup', [[1, 1, 1, 0, 0, 0, 3], -1], [2, True, 3]), ('partial-repair probe', [[1, 0, 0, 0, 0], -1], [0, True, 1]), ('regression: visual slot lookup', [[1, 1, 1, 1, 1, 1, 1, 1, 3], 17], [0, False, 0]), ('click left of RTL line', [[1, 1, 1], -1], [2, True, 3]), ('click past end', [[0, 1, 1], 9], [1, False, 1]), ('control layout', [[1], 3], [0, False, 0]), ('control layout', [[1], -2], [0, True, 1])], [('regression: visual slot lookup', [[3, 3, 0, 0, 0], -2], [1, True, 2]), ('regression: visual slot lookup', [[1, 1, 1, 3, 3], 13], [0, False, 0]), ('regression: visual slot lookup', [[3, 3, 3, 3, 1, 1, 1], -2], [6, True, 7]), ('regression: visual slot lookup', [[0, 0, 0, 2, 2, 3, 3, 3, 3, 1], 20], [5, False, 5]), ('click past end', [[0, 1, 1], 9], [1, False, 1]), ('right half of RTL char', [[1, 1], 1], [1, False, 1]), ('control layout', [[1], 0], [0, True, 1]), ('control layout', [[2, 2, 2], 3], [1, True, 2])]]\nfor label, args, expected in fixtures[N - 1]:\n    check(label, solve(args), expected)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"fixed":{"sha256":"049a09e237a8c71b67dace9b397a4b5555dea1f79aeccde054e28e9c8d326785","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x):\n    def reorder(lv):\n        vis = list(range(len(lv)))\n        odd = [l for l in lv if l % 2 == 1]\n        if not odd:\n            return vis\n        for lev in range(max(lv), min(odd) - 1, -1):\n            i = 0\n            while i < len(vis):\n                if lv[vis[i]] >= lev:\n                    j = i\n                    while j < len(vis) and lv[vis[j]] >= lev:\n                        j += 1\n                    vis[i:j] = vis[i:j][::-1]\n                    i = j\n                else:\n                    i += 1\n        return vis\n    \n    levels, px = x\n    n = len(levels)\n    if n == 0:\n        return [None, False, 0]\n    vis = reorder(levels)\n    v = min(max(px // 2, 0), n - 1)\n    i = vis[v]\n    right_half = px - 2 * v >= 1\n    rtl = levels[i] % 2 == 1\n    trailing = right_half != rtl\n    return [i, trailing, i + 1 if trailing else i]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[('click left of RTL line', [[1, 1, 1], -1], [2, True, 3]), ('regression: visual slot lookup', [[2, 2, 2, 1, 1], 8], [2, False, 2]), ('regression: visual slot lookup', [[1, 1, 1, 1, 3, 3, 0, 1, 2, 2], 1], [5, False, 5]), ('partial-repair probe', [[0, 0, 0, 0], -1], [0, False, 0]), ('click past end', [[0, 1, 1], 9], [1, False, 1]), ('right half of RTL char', [[1, 1], 1], [1, False, 1]), ('control layout', [[1], 4], [0, False, 0]), ('control layout', [[2, 2, 2, 2, 2, 4, 2, 2, 2], 9], [4, True, 5])], [('regression: visual slot lookup', [[1, 1, 1, 3], 10], [0, False, 0]), ('regression: visual slot lookup', [[1, 1, 1, 1, 1, 1], 9], [1, False, 1]), ('regression: visual slot lookup', [[1, 1, 1, 0, 0, 1, 1], -3], [2, True, 3]), ('regression: visual slot lookup', [[1, 1, 2, 2, 2, 3, 3], 16], [0, False, 0]), ('right half of RTL char', [[1, 1], 1], [1, False, 1]), ('click past end', [[0, 1, 1], 9], [1, False, 1]), ('control layout', [[1], 4], [0, False, 0]), ('control layout', [[4, 4, 4, 1, 4, 4, 4], 6], [3, True, 4])], [('regression: visual slot lookup', [[3, 3, 3, 3, 3, 1, 2, 2, 2, 2], 11], [4, False, 4]), ('regression: visual slot lookup', [[1, 2], 7], [0, False, 0]), ('regression: visual slot lookup', [[4, 4, 4, 4, 1, 1], 11], [3, True, 4]), ('regression: visual slot lookup', [[2, 2, 2, 1, 1, 1, 2], 0], [6, False, 6]), ('click past end', [[0, 1, 1], 9], [1, False, 1]), ('click left of RTL line', [[1, 1, 1], -1], [2, True, 3]), ('control layout', [[2], 4], [0, True, 1]), ('control layout', [[1], 3], [0, False, 0])], [('regression: visual slot lookup', [[1, 3, 3, 3, 3, 1, 1, 1], 9], [3, False, 3]), ('regression: visual slot lookup', [[1, 1, 1, 0, 0, 0, 3], -1], [2, True, 3]), ('partial-repair probe', [[1, 0, 0, 0, 0], -1], [0, True, 1]), ('regression: visual slot lookup', [[1, 1, 1, 1, 1, 1, 1, 1, 3], 17], [0, False, 0]), ('click left of RTL line', [[1, 1, 1], -1], [2, True, 3]), ('click past end', [[0, 1, 1], 9], [1, False, 1]), ('control layout', [[1], 3], [0, False, 0]), ('control layout', [[1], -2], [0, True, 1])], [('regression: visual slot lookup', [[3, 3, 0, 0, 0], -2], [1, True, 2]), ('regression: visual slot lookup', [[1, 1, 1, 3, 3], 13], [0, False, 0]), ('regression: visual slot lookup', [[3, 3, 3, 3, 1, 1, 1], -2], [6, True, 7]), ('regression: visual slot lookup', [[0, 0, 0, 2, 2, 3, 3, 3, 3, 1], 20], [5, False, 5]), ('click past end', [[0, 1, 1], 9], [1, False, 1]), ('right half of RTL char', [[1, 1], 1], [1, False, 1]), ('control layout', [[1], 0], [0, True, 1]), ('control layout', [[2, 2, 2], 3], [1, True, 2])]]\nfor label, args, expected in fixtures[N - 1]:\n    check(label, solve(args), expected)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"}},"limitations":"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.","method":"Deterministic executable model with adversarial boundary fixtures.","provenance":{"created_by":"Failure Map","dependencies":"Python standard library","family":"w2-bidirectional-text-layout-hit-testing-visual-slot-lookup","generated_at":"2026-09-29T14:49:56.148023+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"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.","repair":"Look up the logical index at the visual slot.","root_cause":"The slot is used as the logical index.","sha256":"1dde73fb9f02fde11da75d7caabed2d729edf35f0985024d75761090aadd7fe9","title":"Bidi hit testing: visual slot lookup · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":40.762,"exit_code":1,"observations":[{"actual":[0,true,1],"check":"click left of RTL line","expected":[2,true,3],"passed":false},{"actual":[4,true,5],"check":"regression: visual slot lookup","expected":[2,false,2],"passed":false},{"actual":[7,false,7],"check":"regression: visual slot lookup","expected":[5,false,5],"passed":false},{"actual":[3,false,3],"check":"partial-repair probe","expected":[0,false,0],"passed":false},{"actual":[0,true,1],"check":"click past end","expected":[1,false,1],"passed":false},{"actual":[0,false,0],"check":"right half of RTL char","expected":[1,false,1],"passed":false},{"actual":[0,false,0],"check":"control layout","expected":[0,false,0],"passed":true},{"actual":[4,true,5],"check":"control layout","expected":[4,true,5],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"click left of RTL line\", \"actual\": [0, true, 1], \"expected\": [2, true, 3], \"passed\": false}, {\"check\": \"regression: visual slot lookup\", \"actual\": [4, true, 5], \"expected\": [2, false, 2], \"passed\": false}, {\"check\": \"regression: visual slot lookup\", \"actual\": [7, false, 7], \"expected\": [5, false, 5], \"passed\": false}, {\"check\": \"partial-repair probe\", \"actual\": [3, false, 3], \"expected\": [0, false, 0], \"passed\": false}, {\"check\": \"click past end\", \"actual\": [0, true, 1], \"expected\": [1, false, 1], \"passed\": false}, {\"check\": \"right half of RTL char\", \"actual\": [0, false, 0], \"expected\": [1, false, 1], \"passed\": false}, {\"check\": \"control layout\", \"actual\": [0, false, 0], \"expected\": [0, false, 0], \"passed\": true}, {\"check\": \"control layout\", \"actual\": [4, true, 5], \"expected\": [4, true, 5], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":39.025,"exit_code":1,"observations":[{"actual":[0,true,1],"check":"click left of RTL line","expected":[2,true,3],"passed":false},{"actual":[4,true,5],"check":"regression: visual slot lookup","expected":[2,false,2],"passed":false},{"actual":[0,false,0],"check":"regression: visual slot lookup","expected":[5,false,5],"passed":false},{"actual":[0,false,0],"check":"partial-repair probe","expected":[0,false,0],"passed":true},{"actual":[2,false,2],"check":"click past end","expected":[1,false,1],"passed":false},{"actual":[0,false,0],"check":"right half of RTL char","expected":[1,false,1],"passed":false},{"actual":[0,false,0],"check":"control layout","expected":[0,false,0],"passed":true},{"actual":[4,true,5],"check":"control layout","expected":[4,true,5],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"click left of RTL line\", \"actual\": [0, true, 1], \"expected\": [2, true, 3], \"passed\": false}, {\"check\": \"regression: visual slot lookup\", \"actual\": [4, true, 5], \"expected\": [2, false, 2], \"passed\": false}, {\"check\": \"regression: visual slot lookup\", \"actual\": [0, false, 0], \"expected\": [5, false, 5], \"passed\": false}, {\"check\": \"partial-repair probe\", \"actual\": [0, false, 0], \"expected\": [0, false, 0], \"passed\": true}, {\"check\": \"click past end\", \"actual\": [2, false, 2], \"expected\": [1, false, 1], \"passed\": false}, {\"check\": \"right half of RTL char\", \"actual\": [0, false, 0], \"expected\": [1, false, 1], \"passed\": false}, {\"check\": \"control layout\", \"actual\": [0, false, 0], \"expected\": [0, false, 0], \"passed\": true}, {\"check\": \"control layout\", \"actual\": [4, true, 5], \"expected\": [4, true, 5], \"passed\": true}], \"passed\": false}\n"},"fixed":{"elapsed_ms":39.972,"exit_code":0,"observations":[{"actual":[2,true,3],"check":"click left of RTL line","expected":[2,true,3],"passed":true},{"actual":[2,false,2],"check":"regression: visual slot lookup","expected":[2,false,2],"passed":true},{"actual":[5,false,5],"check":"regression: visual slot lookup","expected":[5,false,5],"passed":true},{"actual":[0,false,0],"check":"partial-repair probe","expected":[0,false,0],"passed":true},{"actual":[1,false,1],"check":"click past end","expected":[1,false,1],"passed":true},{"actual":[1,false,1],"check":"right half of RTL char","expected":[1,false,1],"passed":true},{"actual":[0,false,0],"check":"control layout","expected":[0,false,0],"passed":true},{"actual":[4,true,5],"check":"control layout","expected":[4,true,5],"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"click left of RTL line\", \"actual\": [2, true, 3], \"expected\": [2, true, 3], \"passed\": true}, {\"check\": \"regression: visual slot lookup\", \"actual\": [2, false, 2], \"expected\": [2, false, 2], \"passed\": true}, {\"check\": \"regression: visual slot lookup\", \"actual\": [5, false, 5], \"expected\": [5, false, 5], \"passed\": true}, {\"check\": \"partial-repair probe\", \"actual\": [0, false, 0], \"expected\": [0, false, 0], \"passed\": true}, {\"check\": \"click past end\", \"actual\": [1, false, 1], \"expected\": [1, false, 1], \"passed\": true}, {\"check\": \"right half of RTL char\", \"actual\": [1, false, 1], \"expected\": [1, false, 1], \"passed\": true}, {\"check\": \"control layout\", \"actual\": [0, false, 0], \"expected\": [0, false, 0], \"passed\": true}, {\"check\": \"control layout\", \"actual\": [4, true, 5], \"expected\": [4, true, 5], \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}