FA-52982 / Raster memory layout / Member archive

Scanline Scatter Gather: Gather destination overwrites first segment or uses pixel offset · case 02

The returned physical layout descriptor disagrees with the declared buffer mapping at destination_offsets.

Member previewVariant 2 · 3 implementations · 6 checks per implementation

Case contract

A raster readback maps each row to two caller-provided physical segments. Segment boundary is a pixel index, not a byte count; segment two has its own noncontiguous origin. A requested valid x range becomes up to two byte spans. Return the named intermediate layout descriptor and final address fields; all quantities are integer byte offsets unless explicitly stated.

Why this case matters

Offline raster resource, upload, readback, and storage-layout regression model.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
layout fixture 3	`{"destination_offsets": [0, 0], "left_bytes": 12, "left_count": 4, "left_start": 120, "right_bytes": 6, "right_count": 2, "right_local": 0, "right_start": 426, "spans": [[120, 12], [426, 6]], "total_bytes": 18}`	`{"destination_offsets": [0, 12], "left_bytes": 12, "left_count": 4, "left_start": 120, "right_bytes": 6, "right_count": 2, "right_local": 0, "right_start": 426, "spans": [[120, 12], [426, 6]], "total_bytes": 18}`	Failed

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