{"abstract":"The caret lands on the wrong side of the hit character.","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":"Using the visual half instead of the logical side misplaces RTL carets.","family":"w2-bidirectional-text-layout-hit-testing-caret-offset-from-edge","id":"FA-80706","implementations":{"attempt":{"sha256":"a723bd0d79329dcb10279f885383036ea42be87b110a5824ae4d64858d879484","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 right_half 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: caret offset from edge', [[2, 2, 0, 0, 0], 13], [4, True, 5]), ('regression: caret offset from edge', [[3, 3], 5], [0, False, 0]), ('click past end', [[0, 1, 1], 9], [1, False, 1]), ('right half of RTL char', [[1, 1], 1], [1, False, 1]), ('regression: caret offset from edge', [[3, 3, 3, 1, 1, 1, 1, 1, 1, 3], 6], [6, True, 7]), ('regression: caret offset from edge', [[4, 1, 1, 1], 11], [0, True, 1]), ('regression: caret offset from edge', [[3, 3], -1], [1, True, 2])], [('regression: caret offset from edge', [[3, 3, 3, 3, 4, 4, 4, 1], 8], [3, True, 4]), ('regression: caret offset from edge', [[2, 2, 2, 2], -2], [0, False, 0]), ('regression: caret offset from edge', [[1, 1, 1, 4, 4, 2, 2], 17], [0, False, 0]), ('regression: caret offset from edge', [[1, 1, 1, 1, 1, 3, 3, 3, 3], -1], [8, True, 9]), ('click past end', [[0, 1, 1], 9], [1, False, 1]), ('click left of RTL line', [[1, 1, 1], -1], [2, True, 3]), ('regression: caret offset from edge', [[0, 1, 1, 1, 1, 0, 0, 0], 15], [7, True, 8]), ('regression: caret offset from edge', [[0, 0], 7], [1, True, 2])], [('regression: caret offset from edge', [[2, 2, 2, 2], 4], [2, False, 2]), ('regression: caret offset from edge', [[1, 1, 1, 1, 2, 2, 2, 2, 3, 2], 23], [0, False, 0]), ('click past end', [[0, 1, 1], 9], [1, False, 1]), ('regression: caret offset from edge', [[1, 1, 1, 2, 2, 2, 2, 1, 1, 1], -3], [9, True, 10]), ('right half of RTL char', [[1, 1], 1], [1, False, 1]), ('click left of RTL line', [[1, 1, 1], -1], [2, True, 3]), ('regression: caret offset from edge', [[1], -2], [0, True, 1]), ('regression: caret offset from edge', [[4, 4, 4, 4, 4, 4, 4, 2, 2, 2], 8], [4, False, 4])], [('regression: caret offset from edge', [[0, 0, 0, 1, 1, 1, 1, 3, 3], 3], [1, True, 2]), ('regression: caret offset from edge', [[1, 1, 1, 1, 1, 1, 0, 0, 3], 6], [2, True, 3]), ('regression: caret offset from edge', [[1, 1, 1], 8], [0, False, 0]), ('regression: caret offset from edge', [[3, 3, 3, 3, 1, 1, 1], -2], [6, True, 7]), ('right half of RTL char', [[1, 1], 1], [1, False, 1]), ('click past end', [[0, 1, 1], 9], [1, False, 1]), ('regression: caret offset from edge', [[2, 2, 3, 3, 1, 1, 1], 8], [1, False, 1]), ('regression: caret offset from edge', [[1, 1, 1, 1, 1, 3, 3, 3, 3], -1], [8, True, 9])], [('regression: caret offset from edge', [[3, 3, 3, 1, 1, 1, 1, 2], 2], [6, True, 7]), ('regression: caret offset from edge', [[2], 4], [0, True, 1]), ('regression: caret offset from edge', [[3, 3, 3, 2, 2], -2], [2, True, 3]), ('regression: caret offset from edge', [[3, 3, 3, 3, 1, 1, 1, 1], 18], [0, False, 0]), ('right half of RTL char', [[1, 1], 1], [1, False, 1]), ('click left of RTL line', [[1, 1, 1], -1], [2, True, 3]), ('regression: caret offset from edge', [[0, 0, 0, 0, 0, 0, 1, 1, 2, 0], 13], [8, True, 9]), ('regression: caret offset from edge', [[4, 4, 3], 1], [2, False, 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":"73040a7a1852cae761ba16e1eeeb412d575b271440f354ef16f590c2273c91da","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 if trailing else i + 1]\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: caret offset from edge', [[2, 2, 0, 0, 0], 13], [4, True, 5]), ('regression: caret offset from edge', [[3, 3], 5], [0, False, 0]), ('click past end', [[0, 1, 1], 9], [1, False, 1]), ('right half of RTL char', [[1, 1], 1], [1, False, 1]), ('regression: caret offset from edge', [[3, 3, 3, 1, 1, 1, 1, 1, 1, 3], 6], [6, True, 7]), ('regression: caret offset from edge', [[4, 1, 1, 1], 11], [0, True, 1]), ('regression: caret offset from edge', [[3, 3], -1], [1, True, 2])], [('regression: caret offset from edge', [[3, 3, 3, 3, 4, 4, 4, 1], 8], [3, True, 4]), ('regression: caret offset from edge', [[2, 2, 2, 2], -2], [0, False, 0]), ('regression: caret offset from edge', [[1, 1, 1, 4, 4, 2, 2], 17], [0, False, 0]), ('regression: caret offset from edge', [[1, 1, 1, 1, 1, 3, 3, 3, 3], -1], [8, True, 9]), ('click past end', [[0, 1, 1], 9], [1, False, 1]), ('click left of RTL line', [[1, 1, 1], -1], [2, True, 3]), ('regression: caret offset from edge', [[0, 1, 1, 1, 1, 0, 0, 0], 15], [7, True, 8]), ('regression: caret offset from edge', [[0, 0], 7], [1, True, 2])], [('regression: caret offset from edge', [[2, 2, 2, 2], 4], [2, False, 2]), ('regression: caret offset from edge', [[1, 1, 1, 1, 2, 2, 2, 2, 3, 2], 23], [0, False, 0]), ('click past end', [[0, 1, 1], 9], [1, False, 1]), ('regression: caret offset from edge', [[1, 1, 1, 2, 2, 2, 2, 1, 1, 1], -3], [9, True, 10]), ('right half of RTL char', [[1, 1], 1], [1, False, 1]), ('click left of RTL line', [[1, 1, 1], -1], [2, True, 3]), ('regression: caret offset from edge', [[1], -2], [0, True, 1]), ('regression: caret offset from edge', [[4, 4, 4, 4, 4, 4, 4, 2, 2, 2], 8], [4, False, 4])], [('regression: caret offset from edge', [[0, 0, 0, 1, 1, 1, 1, 3, 3], 3], [1, True, 2]), ('regression: caret offset from edge', [[1, 1, 1, 1, 1, 1, 0, 0, 3], 6], [2, True, 3]), ('regression: caret offset from edge', [[1, 1, 1], 8], [0, False, 0]), ('regression: caret offset from edge', [[3, 3, 3, 3, 1, 1, 1], -2], [6, True, 7]), ('right half of RTL char', [[1, 1], 1], [1, False, 1]), ('click past end', [[0, 1, 1], 9], [1, False, 1]), ('regression: caret offset from edge', [[2, 2, 3, 3, 1, 1, 1], 8], [1, False, 1]), ('regression: caret offset from edge', [[1, 1, 1, 1, 1, 3, 3, 3, 3], -1], [8, True, 9])], [('regression: caret offset from edge', [[3, 3, 3, 1, 1, 1, 1, 2], 2], [6, True, 7]), ('regression: caret offset from edge', [[2], 4], [0, True, 1]), ('regression: caret offset from edge', [[3, 3, 3, 2, 2], -2], [2, True, 3]), ('regression: caret offset from edge', [[3, 3, 3, 3, 1, 1, 1, 1], 18], [0, False, 0]), ('right half of RTL char', [[1, 1], 1], [1, False, 1]), ('click left of RTL line', [[1, 1, 1], -1], [2, True, 3]), ('regression: caret offset from edge', [[0, 0, 0, 0, 0, 0, 1, 1, 2, 0], 13], [8, True, 9]), ('regression: caret offset from edge', [[4, 4, 3], 1], [2, False, 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":"861bc74eed49d3fa85763c91549c00bc628883247fbb6e93878a94fdf4761741","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: caret offset from edge', [[2, 2, 0, 0, 0], 13], [4, True, 5]), ('regression: caret offset from edge', [[3, 3], 5], [0, False, 0]), ('click past end', [[0, 1, 1], 9], [1, False, 1]), ('right half of RTL char', [[1, 1], 1], [1, False, 1]), ('regression: caret offset from edge', [[3, 3, 3, 1, 1, 1, 1, 1, 1, 3], 6], [6, True, 7]), ('regression: caret offset from edge', [[4, 1, 1, 1], 11], [0, True, 1]), ('regression: caret offset from edge', [[3, 3], -1], [1, True, 2])], [('regression: caret offset from edge', [[3, 3, 3, 3, 4, 4, 4, 1], 8], [3, True, 4]), ('regression: caret offset from edge', [[2, 2, 2, 2], -2], [0, False, 0]), ('regression: caret offset from edge', [[1, 1, 1, 4, 4, 2, 2], 17], [0, False, 0]), ('regression: caret offset from edge', [[1, 1, 1, 1, 1, 3, 3, 3, 3], -1], [8, True, 9]), ('click past end', [[0, 1, 1], 9], [1, False, 1]), ('click left of RTL line', [[1, 1, 1], -1], [2, True, 3]), ('regression: caret offset from edge', [[0, 1, 1, 1, 1, 0, 0, 0], 15], [7, True, 8]), ('regression: caret offset from edge', [[0, 0], 7], [1, True, 2])], [('regression: caret offset from edge', [[2, 2, 2, 2], 4], [2, False, 2]), ('regression: caret offset from edge', [[1, 1, 1, 1, 2, 2, 2, 2, 3, 2], 23], [0, False, 0]), ('click past end', [[0, 1, 1], 9], [1, False, 1]), ('regression: caret offset from edge', [[1, 1, 1, 2, 2, 2, 2, 1, 1, 1], -3], [9, True, 10]), ('right half of RTL char', [[1, 1], 1], [1, False, 1]), ('click left of RTL line', [[1, 1, 1], -1], [2, True, 3]), ('regression: caret offset from edge', [[1], -2], [0, True, 1]), ('regression: caret offset from edge', [[4, 4, 4, 4, 4, 4, 4, 2, 2, 2], 8], [4, False, 4])], [('regression: caret offset from edge', [[0, 0, 0, 1, 1, 1, 1, 3, 3], 3], [1, True, 2]), ('regression: caret offset from edge', [[1, 1, 1, 1, 1, 1, 0, 0, 3], 6], [2, True, 3]), ('regression: caret offset from edge', [[1, 1, 1], 8], [0, False, 0]), ('regression: caret offset from edge', [[3, 3, 3, 3, 1, 1, 1], -2], [6, True, 7]), ('right half of RTL char', [[1, 1], 1], [1, False, 1]), ('click past end', [[0, 1, 1], 9], [1, False, 1]), ('regression: caret offset from edge', [[2, 2, 3, 3, 1, 1, 1], 8], [1, False, 1]), ('regression: caret offset from edge', [[1, 1, 1, 1, 1, 3, 3, 3, 3], -1], [8, True, 9])], [('regression: caret offset from edge', [[3, 3, 3, 1, 1, 1, 1, 2], 2], [6, True, 7]), ('regression: caret offset from edge', [[2], 4], [0, True, 1]), ('regression: caret offset from edge', [[3, 3, 3, 2, 2], -2], [2, True, 3]), ('regression: caret offset from edge', [[3, 3, 3, 3, 1, 1, 1, 1], 18], [0, False, 0]), ('right half of RTL char', [[1, 1], 1], [1, False, 1]), ('click left of RTL line', [[1, 1, 1], -1], [2, True, 3]), ('regression: caret offset from edge', [[0, 0, 0, 0, 0, 0, 1, 1, 2, 0], 13], [8, True, 9]), ('regression: caret offset from edge', [[4, 4, 3], 1], [2, False, 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-caret-offset-from-edge","generated_at":"2026-09-29T14:49:56.161379+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":"Offset is index + 1 for the trailing side, else index.","root_cause":"The caret offset is inverted relative to the trailing flag.","sha256":"c11b7cb904727f350028f38550e35f9a024e2d61956a00b141bcf6dead96565a","title":"Bidi hit testing: caret offset from edge · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":38.611,"exit_code":1,"observations":[{"actual":[2,true,2],"check":"click left of RTL line","expected":[2,true,3],"passed":false},{"actual":[4,true,5],"check":"regression: caret offset from edge","expected":[4,true,5],"passed":true},{"actual":[0,false,1],"check":"regression: caret offset from edge","expected":[0,false,0],"passed":false},{"actual":[1,false,2],"check":"click past end","expected":[1,false,1],"passed":false},{"actual":[1,false,2],"check":"right half of RTL char","expected":[1,false,1],"passed":false},{"actual":[6,true,6],"check":"regression: caret offset from edge","expected":[6,true,7],"passed":false},{"actual":[0,true,1],"check":"regression: caret offset from edge","expected":[0,true,1],"passed":true},{"actual":[1,true,1],"check":"regression: caret offset from edge","expected":[1,true,2],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"click left of RTL line\", \"actual\": [2, true, 2], \"expected\": [2, true, 3], \"passed\": false}, {\"check\": \"regression: caret offset from edge\", \"actual\": [4, true, 5], \"expected\": [4, true, 5], \"passed\": true}, {\"check\": \"regression: caret offset from edge\", \"actual\": [0, false, 1], \"expected\": [0, false, 0], \"passed\": false}, {\"check\": \"click past end\", \"actual\": [1, false, 2], \"expected\": [1, false, 1], \"passed\": false}, {\"check\": \"right half of RTL char\", \"actual\": [1, false, 2], \"expected\": [1, false, 1], \"passed\": false}, {\"check\": \"regression: caret offset from edge\", \"actual\": [6, true, 6], \"expected\": [6, true, 7], \"passed\": false}, {\"check\": \"regression: caret offset from edge\", \"actual\": [0, true, 1], \"expected\": [0, true, 1], \"passed\": true}, {\"check\": \"regression: caret offset from edge\", \"actual\": [1, true, 1], \"expected\": [1, true, 2], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":38.408,"exit_code":1,"observations":[{"actual":[2,true,2],"check":"click left of RTL line","expected":[2,true,3],"passed":false},{"actual":[4,true,4],"check":"regression: caret offset from edge","expected":[4,true,5],"passed":false},{"actual":[0,false,1],"check":"regression: caret offset from edge","expected":[0,false,0],"passed":false},{"actual":[1,false,2],"check":"click past end","expected":[1,false,1],"passed":false},{"actual":[1,false,2],"check":"right half of RTL char","expected":[1,false,1],"passed":false},{"actual":[6,true,6],"check":"regression: caret offset from edge","expected":[6,true,7],"passed":false},{"actual":[0,true,0],"check":"regression: caret offset from edge","expected":[0,true,1],"passed":false},{"actual":[1,true,1],"check":"regression: caret offset from edge","expected":[1,true,2],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"click left of RTL line\", \"actual\": [2, true, 2], \"expected\": [2, true, 3], \"passed\": false}, {\"check\": \"regression: caret offset from edge\", \"actual\": [4, true, 4], \"expected\": [4, true, 5], \"passed\": false}, {\"check\": \"regression: caret offset from edge\", \"actual\": [0, false, 1], \"expected\": [0, false, 0], \"passed\": false}, {\"check\": \"click past end\", \"actual\": [1, false, 2], \"expected\": [1, false, 1], \"passed\": false}, {\"check\": \"right half of RTL char\", \"actual\": [1, false, 2], \"expected\": [1, false, 1], \"passed\": false}, {\"check\": \"regression: caret offset from edge\", \"actual\": [6, true, 6], \"expected\": [6, true, 7], \"passed\": false}, {\"check\": \"regression: caret offset from edge\", \"actual\": [0, true, 0], \"expected\": [0, true, 1], \"passed\": false}, {\"check\": \"regression: caret offset from edge\", \"actual\": [1, true, 1], \"expected\": [1, true, 2], \"passed\": false}], \"passed\": false}\n"},"fixed":{"elapsed_ms":39.303,"exit_code":0,"observations":[{"actual":[2,true,3],"check":"click left of RTL line","expected":[2,true,3],"passed":true},{"actual":[4,true,5],"check":"regression: caret offset from edge","expected":[4,true,5],"passed":true},{"actual":[0,false,0],"check":"regression: caret offset from edge","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":[6,true,7],"check":"regression: caret offset from edge","expected":[6,true,7],"passed":true},{"actual":[0,true,1],"check":"regression: caret offset from edge","expected":[0,true,1],"passed":true},{"actual":[1,true,2],"check":"regression: caret offset from edge","expected":[1,true,2],"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: caret offset from edge\", \"actual\": [4, true, 5], \"expected\": [4, true, 5], \"passed\": true}, {\"check\": \"regression: caret offset from edge\", \"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\": \"regression: caret offset from edge\", \"actual\": [6, true, 7], \"expected\": [6, true, 7], \"passed\": true}, {\"check\": \"regression: caret offset from edge\", \"actual\": [0, true, 1], \"expected\": [0, true, 1], \"passed\": true}, {\"check\": \"regression: caret offset from edge\", \"actual\": [1, true, 2], \"expected\": [1, true, 2], \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}