FA-10646 / Raster clipping / Open access

Clipped blit source offset · case 01

Clamping the destination origin shifts discarded source pixels back into view.

Verified by executionVariant 1 · 4 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Clamping the destination origin shifts discarded source pixels back into view.

VERIFIED REPAIR

Use the stage contract: Blit source row at signed destination x, discarding out-of-range destination pixels while retaining original source alignment.

Unsuccessful approach: A strict lower bound loses the valid pixel at coordinate zero.

Case contract

Blit source row at signed destination x, discarding out-of-range destination pixels while retaining original source alignment.

Why this case matters

A deterministic software graphics stage with explicit channel and coordinate conventions; no hardware, device profile or API behavior is inferred.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(destination, source, x):
    out=list(destination)
    for i,pixel in enumerate(source):
        if 0<=max(0,x)+i<len(out): out[max(0,x)+i]=pixel
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve(*([0, 0, 0], [7, 8, 9], -1)), [8, 9, 0])
check('fixture 2', solve(*([0, 0, 0], [7, 8], 2)), [0, 0, 7])
check('fixture 3', solve(*([0, 0], [7], 0)), [7, 0])
check('fixture 4', solve(*([0, 0], [7], 3)), [0, 0])
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
fixture 1	`[7, 8, 9]`	`[8, 9, 0]`	Failed
fixture 2	`[0, 0, 7]`	`[0, 0, 7]`	Passed
fixture 3	`[7, 0]`	`[7, 0]`	Passed
fixture 4	`[0, 0]`	`[0, 0]`	Passed

SHA-256 / e27f3fc243b3241be989348a131f12a9153a1c2ebcd3494a93dd34be9766c298

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(destination, source, x):
    out=list(destination)
    for i,pixel in enumerate(source):
        if 0<x+i<len(out): out[x+i]=pixel
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve(*([0, 0, 0], [7, 8, 9], -1)), [8, 9, 0])
check('fixture 2', solve(*([0, 0, 0], [7, 8], 2)), [0, 0, 7])
check('fixture 3', solve(*([0, 0], [7], 0)), [7, 0])
check('fixture 4', solve(*([0, 0], [7], 3)), [0, 0])
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
fixture 1	`[0, 9, 0]`	`[8, 9, 0]`	Failed
fixture 2	`[0, 0, 7]`	`[0, 0, 7]`	Passed
fixture 3	`[0, 0]`	`[7, 0]`	Failed
fixture 4	`[0, 0]`	`[0, 0]`	Passed

SHA-256 / ffccc164c26ad4d38be701d8d1c5eb177391ca921aa1ea0cad5864ca0f34a687

3 / The verified repair

Exit 0

"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(destination, source, x):
    out=list(destination)
    for i,pixel in enumerate(source):
        if 0<=x+i<len(out): out[x+i]=pixel
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve(*([0, 0, 0], [7, 8, 9], -1)), [8, 9, 0])
check('fixture 2', solve(*([0, 0, 0], [7, 8], 2)), [0, 0, 7])
check('fixture 3', solve(*([0, 0], [7], 0)), [7, 0])
check('fixture 4', solve(*([0, 0], [7], 3)), [0, 0])
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
fixture 1	`[8, 9, 0]`	`[8, 9, 0]`	Passed
fixture 2	`[0, 0, 7]`	`[0, 0, 7]`	Passed
fixture 3	`[7, 0]`	`[7, 0]`	Passed
fixture 4	`[0, 0]`	`[0, 0]`	Passed

SHA-256 / e8f310b1c469ac2342f981426ccdbc30471503bd9c3109147db61bc7e9952bd3

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 2026-09-29T14:38:40.953007+00:00.

Case digest / 5ef8fbfae8ad0d36d91a7d8baac6b10bdc27856b4fb7a1b1ecaf53cfd8487362