FA-52945 / Raster memory layout / Member archive

Scanline Scatter Gather: First segment length ignores request origin or request endpoint · case 05

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

Member previewVariant 5 · 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], "left_bytes": 36, "left_count": 6, "left_start": 147, "right_bytes": 0, "right_count": 0, "right_local": 0, "right_start": 426, "spans": [[147, 36]], "total_bytes": 36}`	`{"destination_offsets": [0, 24], "left_bytes": 24, "left_count": 4, "left_start": 147, "right_bytes": 12, "right_count": 2, "right_local": 0, "right_start": 426, "spans": [[147, 24], [426, 12]], "total_bytes": 36}`	Failed

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