FA-51561 / Raster clipping / Open access

Cohen sutherland pixel window: window uses pixel count · case 01

The window maximum uses the pixel count rather than the last pixel center, letting clipped endpoints land one pixel beyond the raster.

Verified by executionVariant 1 · 16 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The window maximum uses the pixel count rather than the last pixel center, letting clipped endpoints land one pixel beyond the raster.

VERIFIED REPAIR

Restore the specified clipping decision at window uses pixel count. Each command is a segment [x0,y0,x1,y1] whose endpoints are integers or exact decimal/rational strings in pixel-center coordinates. The window is the closed square [0,size-1]x[0,size-1] of pixel centers. Outcodes use strict outside tests (left 1, right 2, below 4, above 8). Both codes zero accepts; a shared bit rejects; otherwise the outside endpoint (endpoint 0 first) is moved to the highest set edge in above, below, right, left order and its code is recomputed from the new point; a clip against an edge parallel to the segment is treated as a rejection. At most five iterations are allowed; an unresolved or rejected segment returns None. Accepted endpoints round half-up to integer pixels.

Unsuccessful approach: Clipping to the outer pixel edge instead of the last center still rounds clipped endpoints up to the out-of-range pixel.

Case contract

Each command is a segment [x0,y0,x1,y1] whose endpoints are integers or exact decimal/rational strings in pixel-center coordinates. The window is the closed square [0,size-1]x[0,size-1] of pixel centers. Outcodes use strict outside tests (left 1, right 2, below 4, above 8). Both codes zero accepts; a shared bit rejects; otherwise the outside endpoint (endpoint 0 first) is moved to the highest set edge in above, below, right, left order and its code is recomputed from the new point; a clip against an edge parallel to the segment is treated as a rejection. At most five iterations are allowed; an unresolved or rejected segment returns None. Accepted endpoints round half-up to integer pixels.

Why this case matters

Raster clipping decides which pixels a primitive may touch; a single wrong clip decision writes outside the target or scissor, or silently drops visible coverage.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
from fractions import Fraction
N = 1
observations = []
def solve(commands, size):
    lo=0
    hi=size
    def code(x,y):
        c=0
        if x<lo: c|=1
        elif x>hi: c|=2
        if y<lo: c|=4
        elif y>hi: c|=8
        return c
    out=[]
    for x0,y0,x1,y1 in commands:
        x0,y0,x1,y1=[Fraction(v) for v in (x0,y0,x1,y1)]
        c0,c1=code(x0,y0),code(x1,y1)
        result=None
        for _ in range(5):
            if not (c0|c1):
                result=[int((v+Fraction(1,2))//1) for v in (x0,y0,x1,y1)]
                break
            if c0&c1: break
            c=c0 if c0 else c1
            if c&12 and y1==y0 or c&3 and x1==x0: break
            if c&8: x,y=x0+(x1-x0)*(hi-y0)/(y1-y0),Fraction(hi)
            elif c&4: x,y=x0+(x1-x0)*(lo-y0)/(y1-y0),Fraction(lo)
            elif c&2: x,y=Fraction(hi),y0+(y1-y0)*(hi-x0)/(x1-x0)
            else: x,y=Fraction(lo),y0+(y1-y0)*(lo-x0)/(x1-x0)
            if c==c0:
                x0,y0=x,y
                c0=code(x0,y0)
            else:
                x1,y1=x,y
                c1=code(x1,y1)
        out.append(result)
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
if N == 1:
    check('explicit case 0', solve([[1, 1, 4, 3]], 6), [[1, 1, 4, 3]])
    check('explicit case 1', solve([[-3, 2, 8, 2]], 6), [[0, 2, 5, 2]])
    check('explicit case 2', solve([[-2, -2, 7, 7]], 6), [[0, 0, 5, 5]])
    check('explicit case 3', solve([[-3, 0, -1, 5]], 6), [None])
    check('explicit case 4', solve([[0, 0, 5, 5]], 6), [[0, 0, 5, 5]])
    check('explicit case 5', solve([[0, 0, '5.8', 0]], 6), [[0, 0, 5, 0]])
    check('explicit case 6', solve([[1, -4, -2, 2]], 6), [None])
    check('explicit case 7', solve([[-2, 1, 3, -4]], 6), [None])
    check('explicit case 8', solve([[-2, 1, 4, 10]], 6), [[0, 4, 1, 5]])
    check('explicit case 9', solve([[0, '2.5', 5, '2.5']], 6), [[0, 3, 5, 3]])
    check('explicit case 10', solve([[0, '1.5', 2, '1.5']], 6), [[0, 2, 2, 2]])
    check('explicit case 11', solve([[0, 0, 9, 0]], 6), [[0, 0, 5, 0]])
    check('explicit case 12', solve([['-5', '-7/2', '10', '17/2']], 6), [[0, 1, 5, 5]])
    check('explicit case 13', solve([[2, 1, 4, 11]], 6), [[2, 1, 3, 5]])
    check('explicit case 14', solve([[3, 8, 1, -2]], 6), [[2, 5, 1, 0]])
    check('explicit case 15', solve([[8, 1, 1, 9]], 6), [[5, 4, 5, 5]])
if N == 2:
    check('explicit case 0', solve([[1, 1, 5, 4]], 7), [[1, 1, 5, 4]])
    check('explicit case 1', solve([[-3, 2, 9, 2]], 7), [[0, 2, 6, 2]])
    check('explicit case 2', solve([[-2, -2, 8, 8]], 7), [[0, 0, 6, 6]])
    check('explicit case 3', solve([[-3, 0, -1, 6]], 7), [None])
    check('explicit case 4', solve([[0, 0, 6, 6]], 7), [[0, 0, 6, 6]])
    check('explicit case 5', solve([[0, 0, '6.8', 0]], 7), [[0, 0, 6, 0]])
    check('explicit case 6', solve([[1, -4, -2, 2]], 7), [None])
    check('explicit case 7', solve([[-2, 1, 3, -4]], 7), [None])
    check('explicit case 8', solve([[-2, 1, 4, 11]], 7), [[0, 4, 1, 6]])
    check('explicit case 9', solve([[0, '2.5', 6, '2.5']], 7), [[0, 3, 6, 3]])
    check('explicit case 10', solve([[0, '1.5', 2, '1.5']], 7), [[0, 2, 2, 2]])
    check('explicit case 11', solve([[0, 0, 10, 0]], 7), [[0, 0, 6, 0]])
    check('explicit case 12', solve([['-6', '-9/2', '12', '21/2']], 7), [[0, 1, 6, 6]])
    check('explicit case 13', solve([[2, 1, 4, 12]], 7), [[2, 1, 3, 6]])
    check('explicit case 14', solve([[3, 9, 1, -2]], 7), [[2, 6, 1, 0]])
    check('explicit case 15', solve([[9, 1, 1, 10]], 7), [[6, 4, 5, 6]])
if N == 3:
    check('explicit case 0', solve([[1, 1, 6, 5]], 8), [[1, 1, 6, 5]])
    check('explicit case 1', solve([[-3, 2, 10, 2]], 8), [[0, 2, 7, 2]])
    check('explicit case 2', solve([[-2, -2, 9, 9]], 8), [[0, 0, 7, 7]])
    check('explicit case 3', solve([[-3, 0, -1, 7]], 8), [None])
    check('explicit case 4', solve([[0, 0, 7, 7]], 8), [[0, 0, 7, 7]])
    check('explicit case 5', solve([[0, 0, '7.8', 0]], 8), [[0, 0, 7, 0]])
    check('explicit case 6', solve([[1, -4, -2, 2]], 8), [None])
    check('explicit case 7', solve([[-2, 1, 3, -4]], 8), [None])
    check('explicit case 8', solve([[-2, 1, 4, 12]], 8), [[0, 5, 1, 7]])
    check('explicit case 9', solve([[0, '2.5', 7, '2.5']], 8), [[0, 3, 7, 3]])
    check('explicit case 10', solve([[0, '1.5', 2, '1.5']], 8), [[0, 2, 2, 2]])
    check('explicit case 11', solve([[0, 0, 11, 0]], 8), [[0, 0, 7, 0]])
    check('explicit case 12', solve([['-7', '-11/2', '14', '25/2']], 8), [[0, 1, 7, 7]])
    check('explicit case 13', solve([[2, 1, 4, 13]], 8), [[2, 1, 3, 7]])
    check('explicit case 14', solve([[3, 10, 1, -2]], 8), [[3, 7, 1, 0]])
    check('explicit case 15', solve([[10, 1, 1, 11]], 8), [[7, 4, 5, 7]])
if N == 4:
    check('explicit case 0', solve([[1, 1, 7, 6]], 9), [[1, 1, 7, 6]])
    check('explicit case 1', solve([[-3, 2, 11, 2]], 9), [[0, 2, 8, 2]])
    check('explicit case 2', solve([[-2, -2, 10, 10]], 9), [[0, 0, 8, 8]])
    check('explicit case 3', solve([[-3, 0, -1, 8]], 9), [None])
    check('explicit case 4', solve([[0, 0, 8, 8]], 9), [[0, 0, 8, 8]])
    check('explicit case 5', solve([[0, 0, '8.8', 0]], 9), [[0, 0, 8, 0]])
    check('explicit case 6', solve([[1, -4, -2, 2]], 9), [None])
    check('explicit case 7', solve([[-2, 1, 3, -4]], 9), [None])
    check('explicit case 8', solve([[-2, 1, 4, 13]], 9), [[0, 5, 2, 8]])
    check('explicit case 9', solve([[0, '2.5', 8, '2.5']], 9), [[0, 3, 8, 3]])
    check('explicit case 10', solve([[0, '1.5', 2, '1.5']], 9), [[0, 2, 2, 2]])
    check('explicit case 11', solve([[0, 0, 12, 0]], 9), [[0, 0, 8, 0]])
    check('explicit case 12', solve([['-8', '-13/2', '16', '29/2']], 9), [[0, 1, 8, 8]])
    check('explicit case 13', solve([[2, 1, 4, 14]], 9), [[2, 1, 3, 8]])
    check('explicit case 14', solve([[3, 11, 1, -2]], 9), [[3, 8, 1, 0]])
    check('explicit case 15', solve([[11, 1, 1, 12]], 9), [[8, 4, 5, 8]])
if N == 5:
    check('explicit case 0', solve([[1, 1, 8, 7]], 10), [[1, 1, 8, 7]])
    check('explicit case 1', solve([[-3, 2, 12, 2]], 10), [[0, 2, 9, 2]])
    check('explicit case 2', solve([[-2, -2, 11, 11]], 10), [[0, 0, 9, 9]])
    check('explicit case 3', solve([[-3, 0, -1, 9]], 10), [None])
    check('explicit case 4', solve([[0, 0, 9, 9]], 10), [[0, 0, 9, 9]])
    check('explicit case 5', solve([[0, 0, '9.8', 0]], 10), [[0, 0, 9, 0]])
    check('explicit case 6', solve([[1, -4, -2, 2]], 10), [None])
    check('explicit case 7', solve([[-2, 1, 3, -4]], 10), [None])
    check('explicit case 8', solve([[-2, 1, 4, 14]], 10), [[0, 5, 2, 9]])
    check('explicit case 9', solve([[0, '2.5', 9, '2.5']], 10), [[0, 3, 9, 3]])
    check('explicit case 10', solve([[0, '1.5', 2, '1.5']], 10), [[0, 2, 2, 2]])
    check('explicit case 11', solve([[0, 0, 13, 0]], 10), [[0, 0, 9, 0]])
    check('explicit case 12', solve([['-9', '-15/2', '18', '33/2']], 10), [[0, 1, 9, 9]])
    check('explicit case 13', solve([[2, 1, 4, 15]], 10), [[2, 1, 3, 9]])
    check('explicit case 14', solve([[3, 12, 1, -2]], 10), [[3, 9, 1, 0]])
    check('explicit case 15', solve([[12, 1, 1, 13]], 10), [[9, 4, 5, 9]])
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 fixture	Actual	Expected	Outcome
explicit case 0	`[[1, 1, 4, 3]]`	`[[1, 1, 4, 3]]`	Passed
explicit case 1	`[[0, 2, 6, 2]]`	`[[0, 2, 5, 2]]`	Failed
explicit case 2	`[[0, 0, 6, 6]]`	`[[0, 0, 5, 5]]`	Failed
explicit case 3	`[None]`	`[None]`	Passed
explicit case 4	`[[0, 0, 5, 5]]`	`[[0, 0, 5, 5]]`	Passed
explicit case 5	`[[0, 0, 6, 0]]`	`[[0, 0, 5, 0]]`	Failed
explicit case 6	`[None]`	`[None]`	Passed
explicit case 7	`[None]`	`[None]`	Passed
explicit case 8	`[[0, 4, 1, 6]]`	`[[0, 4, 1, 5]]`	Failed
explicit case 9	`[[0, 3, 5, 3]]`	`[[0, 3, 5, 3]]`	Passed
explicit case 10	`[[0, 2, 2, 2]]`	`[[0, 2, 2, 2]]`	Passed
explicit case 11	`[[0, 0, 6, 0]]`	`[[0, 0, 5, 0]]`	Failed
explicit case 12	`[[0, 1, 6, 5]]`	`[[0, 1, 5, 5]]`	Failed
explicit case 13	`[[2, 1, 3, 6]]`	`[[2, 1, 3, 5]]`	Failed
explicit case 14	`[[3, 6, 1, 0]]`	`[[2, 5, 1, 0]]`	Failed
explicit case 15	`[[6, 3, 4, 6]]`	`[[5, 4, 5, 5]]`	Failed

SHA-256 / 4a1c5004659d66721a05d035683535922d93328415c2a5431a7d44b734b5760e

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
from fractions import Fraction
N = 1
observations = []
def solve(commands, size):
    lo=0
    hi=size-Fraction(1,2)
    def code(x,y):
        c=0
        if x<lo: c|=1
        elif x>hi: c|=2
        if y<lo: c|=4
        elif y>hi: c|=8
        return c
    out=[]
    for x0,y0,x1,y1 in commands:
        x0,y0,x1,y1=[Fraction(v) for v in (x0,y0,x1,y1)]
        c0,c1=code(x0,y0),code(x1,y1)
        result=None
        for _ in range(5):
            if not (c0|c1):
                result=[int((v+Fraction(1,2))//1) for v in (x0,y0,x1,y1)]
                break
            if c0&c1: break
            c=c0 if c0 else c1
            if c&12 and y1==y0 or c&3 and x1==x0: break
            if c&8: x,y=x0+(x1-x0)*(hi-y0)/(y1-y0),Fraction(hi)
            elif c&4: x,y=x0+(x1-x0)*(lo-y0)/(y1-y0),Fraction(lo)
            elif c&2: x,y=Fraction(hi),y0+(y1-y0)*(hi-x0)/(x1-x0)
            else: x,y=Fraction(lo),y0+(y1-y0)*(lo-x0)/(x1-x0)
            if c==c0:
                x0,y0=x,y
                c0=code(x0,y0)
            else:
                x1,y1=x,y
                c1=code(x1,y1)
        out.append(result)
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
if N == 1:
    check('explicit case 0', solve([[1, 1, 4, 3]], 6), [[1, 1, 4, 3]])
    check('explicit case 1', solve([[-3, 2, 8, 2]], 6), [[0, 2, 5, 2]])
    check('explicit case 2', solve([[-2, -2, 7, 7]], 6), [[0, 0, 5, 5]])
    check('explicit case 3', solve([[-3, 0, -1, 5]], 6), [None])
    check('explicit case 4', solve([[0, 0, 5, 5]], 6), [[0, 0, 5, 5]])
    check('explicit case 5', solve([[0, 0, '5.8', 0]], 6), [[0, 0, 5, 0]])
    check('explicit case 6', solve([[1, -4, -2, 2]], 6), [None])
    check('explicit case 7', solve([[-2, 1, 3, -4]], 6), [None])
    check('explicit case 8', solve([[-2, 1, 4, 10]], 6), [[0, 4, 1, 5]])
    check('explicit case 9', solve([[0, '2.5', 5, '2.5']], 6), [[0, 3, 5, 3]])
    check('explicit case 10', solve([[0, '1.5', 2, '1.5']], 6), [[0, 2, 2, 2]])
    check('explicit case 11', solve([[0, 0, 9, 0]], 6), [[0, 0, 5, 0]])
    check('explicit case 12', solve([['-5', '-7/2', '10', '17/2']], 6), [[0, 1, 5, 5]])
    check('explicit case 13', solve([[2, 1, 4, 11]], 6), [[2, 1, 3, 5]])
    check('explicit case 14', solve([[3, 8, 1, -2]], 6), [[2, 5, 1, 0]])
    check('explicit case 15', solve([[8, 1, 1, 9]], 6), [[5, 4, 5, 5]])
if N == 2:
    check('explicit case 0', solve([[1, 1, 5, 4]], 7), [[1, 1, 5, 4]])
    check('explicit case 1', solve([[-3, 2, 9, 2]], 7), [[0, 2, 6, 2]])
    check('explicit case 2', solve([[-2, -2, 8, 8]], 7), [[0, 0, 6, 6]])
    check('explicit case 3', solve([[-3, 0, -1, 6]], 7), [None])
    check('explicit case 4', solve([[0, 0, 6, 6]], 7), [[0, 0, 6, 6]])
    check('explicit case 5', solve([[0, 0, '6.8', 0]], 7), [[0, 0, 6, 0]])
    check('explicit case 6', solve([[1, -4, -2, 2]], 7), [None])
    check('explicit case 7', solve([[-2, 1, 3, -4]], 7), [None])
    check('explicit case 8', solve([[-2, 1, 4, 11]], 7), [[0, 4, 1, 6]])
    check('explicit case 9', solve([[0, '2.5', 6, '2.5']], 7), [[0, 3, 6, 3]])
    check('explicit case 10', solve([[0, '1.5', 2, '1.5']], 7), [[0, 2, 2, 2]])
    check('explicit case 11', solve([[0, 0, 10, 0]], 7), [[0, 0, 6, 0]])
    check('explicit case 12', solve([['-6', '-9/2', '12', '21/2']], 7), [[0, 1, 6, 6]])
    check('explicit case 13', solve([[2, 1, 4, 12]], 7), [[2, 1, 3, 6]])
    check('explicit case 14', solve([[3, 9, 1, -2]], 7), [[2, 6, 1, 0]])
    check('explicit case 15', solve([[9, 1, 1, 10]], 7), [[6, 4, 5, 6]])
if N == 3:
    check('explicit case 0', solve([[1, 1, 6, 5]], 8), [[1, 1, 6, 5]])
    check('explicit case 1', solve([[-3, 2, 10, 2]], 8), [[0, 2, 7, 2]])
    check('explicit case 2', solve([[-2, -2, 9, 9]], 8), [[0, 0, 7, 7]])
    check('explicit case 3', solve([[-3, 0, -1, 7]], 8), [None])
    check('explicit case 4', solve([[0, 0, 7, 7]], 8), [[0, 0, 7, 7]])
    check('explicit case 5', solve([[0, 0, '7.8', 0]], 8), [[0, 0, 7, 0]])
    check('explicit case 6', solve([[1, -4, -2, 2]], 8), [None])
    check('explicit case 7', solve([[-2, 1, 3, -4]], 8), [None])
    check('explicit case 8', solve([[-2, 1, 4, 12]], 8), [[0, 5, 1, 7]])
    check('explicit case 9', solve([[0, '2.5', 7, '2.5']], 8), [[0, 3, 7, 3]])
    check('explicit case 10', solve([[0, '1.5', 2, '1.5']], 8), [[0, 2, 2, 2]])
    check('explicit case 11', solve([[0, 0, 11, 0]], 8), [[0, 0, 7, 0]])
    check('explicit case 12', solve([['-7', '-11/2', '14', '25/2']], 8), [[0, 1, 7, 7]])
    check('explicit case 13', solve([[2, 1, 4, 13]], 8), [[2, 1, 3, 7]])
    check('explicit case 14', solve([[3, 10, 1, -2]], 8), [[3, 7, 1, 0]])
    check('explicit case 15', solve([[10, 1, 1, 11]], 8), [[7, 4, 5, 7]])
if N == 4:
    check('explicit case 0', solve([[1, 1, 7, 6]], 9), [[1, 1, 7, 6]])
    check('explicit case 1', solve([[-3, 2, 11, 2]], 9), [[0, 2, 8, 2]])
    check('explicit case 2', solve([[-2, -2, 10, 10]], 9), [[0, 0, 8, 8]])
    check('explicit case 3', solve([[-3, 0, -1, 8]], 9), [None])
    check('explicit case 4', solve([[0, 0, 8, 8]], 9), [[0, 0, 8, 8]])
    check('explicit case 5', solve([[0, 0, '8.8', 0]], 9), [[0, 0, 8, 0]])
    check('explicit case 6', solve([[1, -4, -2, 2]], 9), [None])
    check('explicit case 7', solve([[-2, 1, 3, -4]], 9), [None])
    check('explicit case 8', solve([[-2, 1, 4, 13]], 9), [[0, 5, 2, 8]])
    check('explicit case 9', solve([[0, '2.5', 8, '2.5']], 9), [[0, 3, 8, 3]])
    check('explicit case 10', solve([[0, '1.5', 2, '1.5']], 9), [[0, 2, 2, 2]])
    check('explicit case 11', solve([[0, 0, 12, 0]], 9), [[0, 0, 8, 0]])
    check('explicit case 12', solve([['-8', '-13/2', '16', '29/2']], 9), [[0, 1, 8, 8]])
    check('explicit case 13', solve([[2, 1, 4, 14]], 9), [[2, 1, 3, 8]])
    check('explicit case 14', solve([[3, 11, 1, -2]], 9), [[3, 8, 1, 0]])
    check('explicit case 15', solve([[11, 1, 1, 12]], 9), [[8, 4, 5, 8]])
if N == 5:
    check('explicit case 0', solve([[1, 1, 8, 7]], 10), [[1, 1, 8, 7]])
    check('explicit case 1', solve([[-3, 2, 12, 2]], 10), [[0, 2, 9, 2]])
    check('explicit case 2', solve([[-2, -2, 11, 11]], 10), [[0, 0, 9, 9]])
    check('explicit case 3', solve([[-3, 0, -1, 9]], 10), [None])
    check('explicit case 4', solve([[0, 0, 9, 9]], 10), [[0, 0, 9, 9]])
    check('explicit case 5', solve([[0, 0, '9.8', 0]], 10), [[0, 0, 9, 0]])
    check('explicit case 6', solve([[1, -4, -2, 2]], 10), [None])
    check('explicit case 7', solve([[-2, 1, 3, -4]], 10), [None])
    check('explicit case 8', solve([[-2, 1, 4, 14]], 10), [[0, 5, 2, 9]])
    check('explicit case 9', solve([[0, '2.5', 9, '2.5']], 10), [[0, 3, 9, 3]])
    check('explicit case 10', solve([[0, '1.5', 2, '1.5']], 10), [[0, 2, 2, 2]])
    check('explicit case 11', solve([[0, 0, 13, 0]], 10), [[0, 0, 9, 0]])
    check('explicit case 12', solve([['-9', '-15/2', '18', '33/2']], 10), [[0, 1, 9, 9]])
    check('explicit case 13', solve([[2, 1, 4, 15]], 10), [[2, 1, 3, 9]])
    check('explicit case 14', solve([[3, 12, 1, -2]], 10), [[3, 9, 1, 0]])
    check('explicit case 15', solve([[12, 1, 1, 13]], 10), [[9, 4, 5, 9]])
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 fixture	Actual	Expected	Outcome
explicit case 0	`[[1, 1, 4, 3]]`	`[[1, 1, 4, 3]]`	Passed
explicit case 1	`[[0, 2, 6, 2]]`	`[[0, 2, 5, 2]]`	Failed
explicit case 2	`[[0, 0, 6, 6]]`	`[[0, 0, 5, 5]]`	Failed
explicit case 3	`[None]`	`[None]`	Passed
explicit case 4	`[[0, 0, 5, 5]]`	`[[0, 0, 5, 5]]`	Passed
explicit case 5	`[[0, 0, 6, 0]]`	`[[0, 0, 5, 0]]`	Failed
explicit case 6	`[None]`	`[None]`	Passed
explicit case 7	`[None]`	`[None]`	Passed
explicit case 8	`[[0, 4, 1, 6]]`	`[[0, 4, 1, 5]]`	Failed
explicit case 9	`[[0, 3, 5, 3]]`	`[[0, 3, 5, 3]]`	Passed
explicit case 10	`[[0, 2, 2, 2]]`	`[[0, 2, 2, 2]]`	Passed
explicit case 11	`[[0, 0, 6, 0]]`	`[[0, 0, 5, 0]]`	Failed
explicit case 12	`[[0, 1, 6, 5]]`	`[[0, 1, 5, 5]]`	Failed
explicit case 13	`[[2, 1, 3, 6]]`	`[[2, 1, 3, 5]]`	Failed
explicit case 14	`[[3, 6, 1, 0]]`	`[[2, 5, 1, 0]]`	Failed
explicit case 15	`[[6, 4, 4, 6]]`	`[[5, 4, 5, 5]]`	Failed

SHA-256 / c5afc8e211092432a14969ff8ef482231edd69a01ef7fba1a54a838dabc01a02

3 / The verified repair

Exit 0

"""Failure Map reference implementation. Python standard library only."""
import json
from fractions import Fraction
N = 1
observations = []
def solve(commands, size):
    lo=0
    hi=size-1
    def code(x,y):
        c=0
        if x<lo: c|=1
        elif x>hi: c|=2
        if y<lo: c|=4
        elif y>hi: c|=8
        return c
    out=[]
    for x0,y0,x1,y1 in commands:
        x0,y0,x1,y1=[Fraction(v) for v in (x0,y0,x1,y1)]
        c0,c1=code(x0,y0),code(x1,y1)
        result=None
        for _ in range(5):
            if not (c0|c1):
                result=[int((v+Fraction(1,2))//1) for v in (x0,y0,x1,y1)]
                break
            if c0&c1: break
            c=c0 if c0 else c1
            if c&12 and y1==y0 or c&3 and x1==x0: break
            if c&8: x,y=x0+(x1-x0)*(hi-y0)/(y1-y0),Fraction(hi)
            elif c&4: x,y=x0+(x1-x0)*(lo-y0)/(y1-y0),Fraction(lo)
            elif c&2: x,y=Fraction(hi),y0+(y1-y0)*(hi-x0)/(x1-x0)
            else: x,y=Fraction(lo),y0+(y1-y0)*(lo-x0)/(x1-x0)
            if c==c0:
                x0,y0=x,y
                c0=code(x0,y0)
            else:
                x1,y1=x,y
                c1=code(x1,y1)
        out.append(result)
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
if N == 1:
    check('explicit case 0', solve([[1, 1, 4, 3]], 6), [[1, 1, 4, 3]])
    check('explicit case 1', solve([[-3, 2, 8, 2]], 6), [[0, 2, 5, 2]])
    check('explicit case 2', solve([[-2, -2, 7, 7]], 6), [[0, 0, 5, 5]])
    check('explicit case 3', solve([[-3, 0, -1, 5]], 6), [None])
    check('explicit case 4', solve([[0, 0, 5, 5]], 6), [[0, 0, 5, 5]])
    check('explicit case 5', solve([[0, 0, '5.8', 0]], 6), [[0, 0, 5, 0]])
    check('explicit case 6', solve([[1, -4, -2, 2]], 6), [None])
    check('explicit case 7', solve([[-2, 1, 3, -4]], 6), [None])
    check('explicit case 8', solve([[-2, 1, 4, 10]], 6), [[0, 4, 1, 5]])
    check('explicit case 9', solve([[0, '2.5', 5, '2.5']], 6), [[0, 3, 5, 3]])
    check('explicit case 10', solve([[0, '1.5', 2, '1.5']], 6), [[0, 2, 2, 2]])
    check('explicit case 11', solve([[0, 0, 9, 0]], 6), [[0, 0, 5, 0]])
    check('explicit case 12', solve([['-5', '-7/2', '10', '17/2']], 6), [[0, 1, 5, 5]])
    check('explicit case 13', solve([[2, 1, 4, 11]], 6), [[2, 1, 3, 5]])
    check('explicit case 14', solve([[3, 8, 1, -2]], 6), [[2, 5, 1, 0]])
    check('explicit case 15', solve([[8, 1, 1, 9]], 6), [[5, 4, 5, 5]])
if N == 2:
    check('explicit case 0', solve([[1, 1, 5, 4]], 7), [[1, 1, 5, 4]])
    check('explicit case 1', solve([[-3, 2, 9, 2]], 7), [[0, 2, 6, 2]])
    check('explicit case 2', solve([[-2, -2, 8, 8]], 7), [[0, 0, 6, 6]])
    check('explicit case 3', solve([[-3, 0, -1, 6]], 7), [None])
    check('explicit case 4', solve([[0, 0, 6, 6]], 7), [[0, 0, 6, 6]])
    check('explicit case 5', solve([[0, 0, '6.8', 0]], 7), [[0, 0, 6, 0]])
    check('explicit case 6', solve([[1, -4, -2, 2]], 7), [None])
    check('explicit case 7', solve([[-2, 1, 3, -4]], 7), [None])
    check('explicit case 8', solve([[-2, 1, 4, 11]], 7), [[0, 4, 1, 6]])
    check('explicit case 9', solve([[0, '2.5', 6, '2.5']], 7), [[0, 3, 6, 3]])
    check('explicit case 10', solve([[0, '1.5', 2, '1.5']], 7), [[0, 2, 2, 2]])
    check('explicit case 11', solve([[0, 0, 10, 0]], 7), [[0, 0, 6, 0]])
    check('explicit case 12', solve([['-6', '-9/2', '12', '21/2']], 7), [[0, 1, 6, 6]])
    check('explicit case 13', solve([[2, 1, 4, 12]], 7), [[2, 1, 3, 6]])
    check('explicit case 14', solve([[3, 9, 1, -2]], 7), [[2, 6, 1, 0]])
    check('explicit case 15', solve([[9, 1, 1, 10]], 7), [[6, 4, 5, 6]])
if N == 3:
    check('explicit case 0', solve([[1, 1, 6, 5]], 8), [[1, 1, 6, 5]])
    check('explicit case 1', solve([[-3, 2, 10, 2]], 8), [[0, 2, 7, 2]])
    check('explicit case 2', solve([[-2, -2, 9, 9]], 8), [[0, 0, 7, 7]])
    check('explicit case 3', solve([[-3, 0, -1, 7]], 8), [None])
    check('explicit case 4', solve([[0, 0, 7, 7]], 8), [[0, 0, 7, 7]])
    check('explicit case 5', solve([[0, 0, '7.8', 0]], 8), [[0, 0, 7, 0]])
    check('explicit case 6', solve([[1, -4, -2, 2]], 8), [None])
    check('explicit case 7', solve([[-2, 1, 3, -4]], 8), [None])
    check('explicit case 8', solve([[-2, 1, 4, 12]], 8), [[0, 5, 1, 7]])
    check('explicit case 9', solve([[0, '2.5', 7, '2.5']], 8), [[0, 3, 7, 3]])
    check('explicit case 10', solve([[0, '1.5', 2, '1.5']], 8), [[0, 2, 2, 2]])
    check('explicit case 11', solve([[0, 0, 11, 0]], 8), [[0, 0, 7, 0]])
    check('explicit case 12', solve([['-7', '-11/2', '14', '25/2']], 8), [[0, 1, 7, 7]])
    check('explicit case 13', solve([[2, 1, 4, 13]], 8), [[2, 1, 3, 7]])
    check('explicit case 14', solve([[3, 10, 1, -2]], 8), [[3, 7, 1, 0]])
    check('explicit case 15', solve([[10, 1, 1, 11]], 8), [[7, 4, 5, 7]])
if N == 4:
    check('explicit case 0', solve([[1, 1, 7, 6]], 9), [[1, 1, 7, 6]])
    check('explicit case 1', solve([[-3, 2, 11, 2]], 9), [[0, 2, 8, 2]])
    check('explicit case 2', solve([[-2, -2, 10, 10]], 9), [[0, 0, 8, 8]])
    check('explicit case 3', solve([[-3, 0, -1, 8]], 9), [None])
    check('explicit case 4', solve([[0, 0, 8, 8]], 9), [[0, 0, 8, 8]])
    check('explicit case 5', solve([[0, 0, '8.8', 0]], 9), [[0, 0, 8, 0]])
    check('explicit case 6', solve([[1, -4, -2, 2]], 9), [None])
    check('explicit case 7', solve([[-2, 1, 3, -4]], 9), [None])
    check('explicit case 8', solve([[-2, 1, 4, 13]], 9), [[0, 5, 2, 8]])
    check('explicit case 9', solve([[0, '2.5', 8, '2.5']], 9), [[0, 3, 8, 3]])
    check('explicit case 10', solve([[0, '1.5', 2, '1.5']], 9), [[0, 2, 2, 2]])
    check('explicit case 11', solve([[0, 0, 12, 0]], 9), [[0, 0, 8, 0]])
    check('explicit case 12', solve([['-8', '-13/2', '16', '29/2']], 9), [[0, 1, 8, 8]])
    check('explicit case 13', solve([[2, 1, 4, 14]], 9), [[2, 1, 3, 8]])
    check('explicit case 14', solve([[3, 11, 1, -2]], 9), [[3, 8, 1, 0]])
    check('explicit case 15', solve([[11, 1, 1, 12]], 9), [[8, 4, 5, 8]])
if N == 5:
    check('explicit case 0', solve([[1, 1, 8, 7]], 10), [[1, 1, 8, 7]])
    check('explicit case 1', solve([[-3, 2, 12, 2]], 10), [[0, 2, 9, 2]])
    check('explicit case 2', solve([[-2, -2, 11, 11]], 10), [[0, 0, 9, 9]])
    check('explicit case 3', solve([[-3, 0, -1, 9]], 10), [None])
    check('explicit case 4', solve([[0, 0, 9, 9]], 10), [[0, 0, 9, 9]])
    check('explicit case 5', solve([[0, 0, '9.8', 0]], 10), [[0, 0, 9, 0]])
    check('explicit case 6', solve([[1, -4, -2, 2]], 10), [None])
    check('explicit case 7', solve([[-2, 1, 3, -4]], 10), [None])
    check('explicit case 8', solve([[-2, 1, 4, 14]], 10), [[0, 5, 2, 9]])
    check('explicit case 9', solve([[0, '2.5', 9, '2.5']], 10), [[0, 3, 9, 3]])
    check('explicit case 10', solve([[0, '1.5', 2, '1.5']], 10), [[0, 2, 2, 2]])
    check('explicit case 11', solve([[0, 0, 13, 0]], 10), [[0, 0, 9, 0]])
    check('explicit case 12', solve([['-9', '-15/2', '18', '33/2']], 10), [[0, 1, 9, 9]])
    check('explicit case 13', solve([[2, 1, 4, 15]], 10), [[2, 1, 3, 9]])
    check('explicit case 14', solve([[3, 12, 1, -2]], 10), [[3, 9, 1, 0]])
    check('explicit case 15', solve([[12, 1, 1, 13]], 10), [[9, 4, 5, 9]])
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 fixture	Actual	Expected	Outcome
explicit case 0	`[[1, 1, 4, 3]]`	`[[1, 1, 4, 3]]`	Passed
explicit case 1	`[[0, 2, 5, 2]]`	`[[0, 2, 5, 2]]`	Passed
explicit case 2	`[[0, 0, 5, 5]]`	`[[0, 0, 5, 5]]`	Passed
explicit case 3	`[None]`	`[None]`	Passed
explicit case 4	`[[0, 0, 5, 5]]`	`[[0, 0, 5, 5]]`	Passed
explicit case 5	`[[0, 0, 5, 0]]`	`[[0, 0, 5, 0]]`	Passed
explicit case 6	`[None]`	`[None]`	Passed
explicit case 7	`[None]`	`[None]`	Passed
explicit case 8	`[[0, 4, 1, 5]]`	`[[0, 4, 1, 5]]`	Passed
explicit case 9	`[[0, 3, 5, 3]]`	`[[0, 3, 5, 3]]`	Passed
explicit case 10	`[[0, 2, 2, 2]]`	`[[0, 2, 2, 2]]`	Passed
explicit case 11	`[[0, 0, 5, 0]]`	`[[0, 0, 5, 0]]`	Passed
explicit case 12	`[[0, 1, 5, 5]]`	`[[0, 1, 5, 5]]`	Passed
explicit case 13	`[[2, 1, 3, 5]]`	`[[2, 1, 3, 5]]`	Passed
explicit case 14	`[[2, 5, 1, 0]]`	`[[2, 5, 1, 0]]`	Passed
explicit case 15	`[[5, 4, 5, 5]]`	`[[5, 4, 5, 5]]`	Passed

SHA-256 / 8885092b602f3d5a6f5769f10ad2a90f91243932b6afd68cbfb3a0c3db9666bb

Verification & scope

Exact integer/rational arithmetic on small stipulated fixtures models the clipping decision only; no memory layout, GPU pipeline, graphics API or standards conformance is claimed. 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 2026-09-29T14:45:20.127241+00:00.

Case digest / 9b12af730c2288a97e3411bb2de10dcdff18f05837b9b43062f42053fc9c5980