Readback destination layout

webgl.readback-layout

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Selected signal results for external comparison. Field statuses, controls and exact values are retained.

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// Test source pending.

Definition

Known pixels, sentinel guards and PACK state across typed destinations and fenced pixel-pack buffers, including independent retrieval offsets.

Find it in the repository

Collector source: core/signals/webgl/readback-layout.ts
Export: measurementModule · Signal object
Field definitions: core/definitions/webgl/readback-layout.ts
Capture membership: Product capture · common/capture/product.ts
Page registration: app/signals/registry.ts
Field projection: core/results/measurement.ts

Execution contract

Signal: webgl.readback-layout
Collector: webgl.readback-layout
API / surface: core/signals/webgl/readback-layout.ts
Timeout: 2250 ms
Companion signals: None
Fixture inputs: Declared requests (listed below)

Exact request inputs

[
  {
    "key": "webgl.readback-layout.responses",
    "inputs": {
      "tight": {
        "bytes": 24,
        "byteOffset": 0,
        "viewLength": 24,
        "dstOffset": 0,
        "rowLength": 0,
        "skipRows": 0,
        "skipPixels": 0,
        "alignment": 4,
        "invalid": null,
        "id": "tight",
        "fixture": "asymmetric-rgba8",
        "framebuffer": [
          8,
          8
        ],
        "rectangle": [
          1,
          2,
          3,
          2
        ],
        "format": "RGBA",
        "type": "UNSIGNED_BYTE",
        "sentinel": 165,
        "pattern": "R=x*29+y;G=y*31+x;B=(x+3*y)*7;A=255"
      },
      "oversized": {
        "bytes": 256,
        "byteOffset": 0,
        "viewLength": 256,
        "dstOffset": 0,
        "rowLength": 0,
        "skipRows": 0,
        "skipPixels": 0,
        "alignment": 4,
        "invalid": null,
        "id": "oversized",
        "fixture": "asymmetric-rgba8",
        "framebuffer": [
          8,
          8
        ],
        "rectangle": [
          1,
          2,
          3,
          2
        ],
        "format": "RGBA",
        "type": "UNSIGNED_BYTE",
        "sentinel": 165,
        "pattern": "R=x*29+y;G=y*31+x;B=(x+3*y)*7;A=255"
      },
      "subview": {
        "bytes": 256,
        "byteOffset": 13,
        "viewLength": 200,
        "dstOffset": 0,
        "rowLength": 0,
        "skipRows": 0,
        "skipPixels": 0,
        "alignment": 4,
        "invalid": null,
        "id": "subview",
        "fixture": "asymmetric-rgba8",
        "framebuffer": [
          8,
          8
        ],
        "rectangle": [
          1,
          2,
          3,
          2
        ],
        "format": "RGBA",
        "type": "UNSIGNED_BYTE",
        "sentinel": 165,
        "pattern": "R=x*29+y;G=y*31+x;B=(x+3*y)*7;A=255"
      },
      "destination-offset": {
        "bytes": 256,
        "byteOffset": 0,
        "viewLength": 256,
        "dstOffset": 7,
        "rowLength": 0,
        "skipRows": 0,
        "skipPixels": 0,
        "alignment": 4,
        "invalid": null,
        "id": "destination-offset",
        "fixture": "asymmetric-rgba8",
        "framebuffer": [
          8,
          8
        ],
        "rectangle": [
          1,
          2,
          3,
          2
        ],
        "format": "RGBA",
        "type": "UNSIGNED_BYTE",
        "sentinel": 165,
        "pattern": "R=x*29+y;G=y*31+x;B=(x+3*y)*7;A=255"
      },
      "alignment-padding": {
        "bytes": 256,
        "byteOffset": 0,
        "viewLength": 256,
        "dstOffset": 0,
        "rowLength": 0,
        "skipRows": 0,
        "skipPixels": 0,
        "alignment": 8,
        "invalid": null,
        "id": "alignment-padding",
        "fixture": "asymmetric-rgba8",
        "framebuffer": [
          8,
          8
        ],
        "rectangle": [
          1,
          2,
          3,
          2
        ],
        "format": "RGBA",
        "type": "UNSIGNED_BYTE",
        "sentinel": 165,
        "pattern": "R=x*29+y;G=y*31+x;B=(x+3*y)*7;A=255"
      },
      "row-length": {
        "bytes": 256,
        "byteOffset": 0,
        "viewLength": 256,
        "dstOffset": 0,
        "rowLength": 5,
        "skipRows": 0,
        "skipPixels": 0,
        "alignment": 4,
        "invalid": null,
        "id": "row-length",
        "fixture": "asymmetric-rgba8",
        "framebuffer": [
          8,
          8
        ],
        "rectangle": [
          1,
          2,
          3,
          2
        ],
        "format": "RGBA",
        "type": "UNSIGNED_BYTE",
        "sentinel": 165,
        "pattern": "R=x*29+y;G=y*31+x;B=(x+3*y)*7;A=255"
      },
      "row-skip": {
        "bytes": 256,
        "byteOffset": 0,
        "viewLength": 256,
        "dstOffset": 0,
        "rowLength": 0,
        "skipRows": 2,
        "skipPixels": 0,
        "alignment": 4,
        "invalid": null,
        "id": "row-skip",
        "fixture": "asymmetric-rgba8",
        "framebuffer": [
          8,
          8
        ],
        "rectangle": [
          1,
          2,
          3,
          2
        ],
        "format": "RGBA",
        "type": "UNSIGNED_BYTE",
        "sentinel": 165,
        "pattern": "R=x*29+y;G=y*31+x;B=(x+3*y)*7;A=255"
      },
      "pixel-skip": {
        "bytes": 256,
        "byteOffset": 0,
        "viewLength": 256,
        "dstOffset": 0,
        "rowLength": 5,
        "skipRows": 0,
        "skipPixels": 1,
        "alignment": 4,
        "invalid": null,
        "id": "pixel-skip",
        "fixture": "asymmetric-rgba8",
        "framebuffer": [
          8,
          8
        ],
        "rectangle": [
          1,
          2,
          3,
          2
        ],
        "format": "RGBA",
        "type": "UNSIGNED_BYTE",
        "sentinel": 165,
        "pattern": "R=x*29+y;G=y*31+x;B=(x+3*y)*7;A=255"
      },
      "combined": {
        "bytes": 256,
        "byteOffset": 9,
        "viewLength": 220,
        "dstOffset": 3,
        "rowLength": 5,
        "skipRows": 1,
        "skipPixels": 1,
        "alignment": 8,
        "invalid": null,
        "id": "combined",
        "fixture": "asymmetric-rgba8",
        "framebuffer": [
          8,
          8
        ],
        "rectangle": [
          1,
          2,
          3,
          2
        ],
        "format": "RGBA",
        "type": "UNSIGNED_BYTE",
        "sentinel": 165,
        "pattern": "R=x*29+y;G=y*31+x;B=(x+3*y)*7;A=255"
      },
      "undersized": {
        "bytes": 23,
        "byteOffset": 0,
        "viewLength": 23,
        "dstOffset": 0,
        "rowLength": 0,
        "skipRows": 0,
        "skipPixels": 0,
        "alignment": 4,
        "invalid": "size",
        "id": "undersized",
        "fixture": "asymmetric-rgba8",
        "framebuffer": [
          8,
          8
        ],
        "rectangle": [
          1,
          2,
          3,
          2
        ],
        "format": "RGBA",
        "type": "UNSIGNED_BYTE",
        "sentinel": 165,
        "pattern": "R=x*29+y;G=y*31+x;B=(x+3*y)*7;A=255"
      },
      "incompatible-type": {
        "bytes": 256,
        "byteOffset": 0,
        "viewLength": 256,
        "dstOffset": 0,
        "rowLength": 0,
        "skipRows": 0,
        "skipPixels": 0,
        "alignment": 4,
        "invalid": "type",
        "id": "incompatible-type",
        "fixture": "asymmetric-rgba8",
        "framebuffer": [
          8,
          8
        ],
        "rectangle": [
          1,
          2,
          3,
          2
        ],
        "format": "RGBA",
        "type": "UNSIGNED_BYTE",
        "sentinel": 165,
        "pattern": "R=x*29+y;G=y*31+x;B=(x+3*y)*7;A=255"
      },
      "pbo-tight": {
        "revision": "pixel-pack-r1",
        "id": "pbo-tight",
        "offset": 0,
        "alignment": 4,
        "rowLength": 0,
        "skipRows": 0,
        "skipPixels": 0,
        "invalid": false,
        "framebuffer": [
          8,
          8
        ],
        "rectangle": [
          1,
          2,
          3,
          2
        ],
        "bytes": 256,
        "sentinel": 165,
        "typedViewByteOffset": 0,
        "typedDestinationElementOffset": 0,
        "getBufferSubData": {
          "sourceByteOffset": 0,
          "viewByteOffset": 7,
          "destinationElementOffset": 3,
          "lengthElements": 256
        }
      },
      "pbo-offset": {
        "revision": "pixel-pack-r1",
        "id": "pbo-offset",
        "offset": 16,
        "alignment": 4,
        "rowLength": 0,
        "skipRows": 0,
        "skipPixels": 0,
        "invalid": false,
        "framebuffer": [
          8,
          8
        ],
        "rectangle": [
          1,
          2,
          3,
          2
        ],
        "bytes": 256,
        "sentinel": 165,
        "typedViewByteOffset": 0,
        "typedDestinationElementOffset": 16,
        "getBufferSubData": {
          "sourceByteOffset": 0,
          "viewByteOffset": 7,
          "destinationElementOffset": 3,
          "lengthElements": 256
        }
      },
      "pbo-padded": {
        "revision": "pixel-pack-r1",
        "id": "pbo-padded",
        "offset": 16,
        "alignment": 8,
        "rowLength": 5,
        "skipRows": 1,
        "skipPixels": 1,
        "invalid": false,
        "framebuffer": [
          8,
          8
        ],
        "rectangle": [
          1,
          2,
          3,
          2
        ],
        "bytes": 256,
        "sentinel": 165,
        "typedViewByteOffset": 0,
        "typedDestinationElementOffset": 16,
        "getBufferSubData": {
          "sourceByteOffset": 0,
          "viewByteOffset": 7,
          "destinationElementOffset": 3,
          "lengthElements": 256
        }
      },
      "pbo-wrong-overload": {
        "revision": "pixel-pack-r1",
        "id": "pbo-wrong-overload",
        "offset": 16,
        "alignment": 4,
        "rowLength": 0,
        "skipRows": 0,
        "skipPixels": 0,
        "invalid": true,
        "framebuffer": [
          8,
          8
        ],
        "rectangle": [
          1,
          2,
          3,
          2
        ],
        "bytes": 256,
        "sentinel": 165,
        "typedViewByteOffset": 0,
        "typedDestinationElementOffset": 16,
        "getBufferSubData": {
          "sourceByteOffset": 0,
          "viewByteOffset": 7,
          "destinationElementOffset": 3,
          "lengthElements": 256
        }
      }
    },
    "controls": {}
  }
]

One collector runs per invocation. Results and JSON select this signal’s fields; any companions execute in the same collector.

Generated source manifest lists runtime files, fixture URLs and content digests for this build. The Source tab provides a copyable console sample.

Run and edit locally

From the repository root, start the Astro app, then open /signals/webgl.readback-layout. Edit the collector source and reload the page to load its new build.

pnpm run dev:web

In a browser module served by this repository’s Vite graph:

import { createCollector } from "/core/collect"
import { measurementModule } from "/core/signals/webgl/readback-layout"

const signal = measurementModule
const collector = createCollector()
const suite = { signals: [signal] }
const result = await collector.collect(suite)

Reuse the collector owner for repeated calls so collection can enforce cleanup. This returns the collector’s raw result; app/signals/projection.ts selects the retained fields shown on this page.

rg -n 'measurementModule' core app tests
pnpm run check
pnpm run test tests/unit/app/focused-projection.test.ts