pcbjam/tests/tools/screenshots/README.md

Screenshot regression + Discord review tooling

One comparison engine + a Discord reporter for the e2e screenshots; baseline updates happen in the morelli review app (https://pcbjam-morelli-staging.pcbjam-staging.workers.dev, repo github.com/PCBJam/morelli).

Source of truth = CI's Linux render. The dev never authors baselines on the Mac (Mac fonts/GL ≠ CI). CI renders on every push and uploads each run's screenshots to R2 (runs/pcbjam/<run-id>/, 30-day retention, upload-run.ts); when a render change is intentional you promote that run's screenshots in morelli. The environment isn't pinned — if the host's Mesa/fonts drift, the gate lights up in Discord and you just re-promote (broad + low-intensity change ⇒ likely drift).

Baselines live entirely in R2, not git. The PNGs sit in a private Cloudflare R2 bucket (pcbjam-ci-screenshots), content-addressed as sha256/<hex>.png and immutable; the R2-HOSTED manifest baselines/pcbjam/manifest.json (written only by morelli + its seed script) pins each <engine>/<name> to a hash. The local baseline-screenshots/ tree and .baseline-manifest.json are gitignored caches — npm run screenshots:fetch-manifest && npm run screenshots:fetch materializes them. Nothing screenshot-related is committed.

Credentials (S3 API, bucket-scoped, region auto):

CI_SCREENSHOTS_S3_ENDPOINT           # https://<account-id>.r2.cloudflarestorage.com
CI_SCREENSHOTS_S3_BUCKET             # optional, default pcbjam-ci-screenshots
CI_SCREENSHOTS_S3_ACCESS_KEY_ID      # read-only pair for fetch; CI's upload step maps in a write pair
CI_SCREENSHOTS_S3_SECRET_ACCESS_KEY

CI holds the read-only pair as repo secrets (plus CI_SCREENSHOTS_S3_WRITE_* for the run-upload step); devs get a read pair from the team vault (ask) and put it in tests/.env (gitignored, auto-loaded by r2-store.ts; shell env vars take precedence):

CI_SCREENSHOTS_S3_ENDPOINT=https://<account-id>.r2.cloudflarestorage.com
CI_SCREENSHOTS_S3_ACCESS_KEY_ID=<access-key-id>
CI_SCREENSHOTS_S3_SECRET_ACCESS_KEY=<secret>

Without credentials, the manifest/baseline fetch and the compare gate skip with a warning (secretless CI callers stay green).

Everything is per-engine. Specs write test-results/<engine>/<name>.png (engine derived from the running browser via stableShot/shotPath); baselines live in baseline-screenshots/<engine>/; the canonical key everywhere in this tooling is <engine>/<name> and captions/attachments carry the engine label. The same spec on chromium + firefox is two independent gated screenshots.

Files

• config.ts — thresholds, baseline dirs, per-engine floors (calibrate!), clustering knobs.
• image-ops.ts — PNG load/save, pixelmatch diff (AA-excluded), connected-component boxes, triptych compositing, size-cap resize.
• compare.ts — the comparison engine: classify per-engine baselines vs test-results/<engine>/ → test-results/screenshot-diff/report.json + triptych/heatmap PNGs. --pair diffs two files.
• perf-report.ts — renders the track-only runtime-perf table (loadMs/openMs/FPS) with Δ vs the previous main run (fetched via gh).
• post-discord.ts — the always-on CI-on-main report: SHA + e2e status + perf table, then screenshot triptychs (batched, size-capped, flood-collapsed).
• noise.ts — calibration: diff two identical-input renders → per-engine noise floor.
• r2-store.ts — minimal aws4fetch S3 client for the CAS bucket (get/put/exists by hash, downloads integrity-checked).
• r2-sync.ts — cache sync: --manifest downloads the R2-hosted baseline manifest, --pull materializes baseline-screenshots/ from it (idempotent, deletes unlisted files), --verify HEADs every hash.
• upload-run.ts — CI-only: upload the run's renders + meta.json to runs/pcbjam/<run-id>/ for morelli (needs the write pair; no-ops without credentials).
• spec-map.ts — best-effort screenshot-name → spec-file attribution for captions (scans stableShot/shotPath literals).

npm scripts (run from tests/)

npm run screenshots:fetch-manifest   # download the R2-hosted baseline manifest (needs read creds)
npm run screenshots:fetch            # materialize the baseline cache from R2 (run before check)
npm run screenshots:check            # gate: baselines vs test-results → report.json (exit 0; add --fail-on-change to gate)
npm run screenshots:report -- --e2e pass   # post the CI report to Discord (main+push only; needs DISCORD_WEBHOOK_URL)
npm run screenshots:noise -- run1/ run2/   # calibrate floors
npm run screenshots:upload-run -- --e2e pass   # CI-only: upload the run's renders for morelli

Baseline promotion (single or bulk) happens in morelli — pick the run, review the diffs, Promote. It copies verbatim bytes into the CAS, updates the R2 manifest atomically (with provenance: which run/branch/user), and snapshots the previous manifest for revert.

Activation checklist

• Baseline manifest migrated to R2 (baselines/pcbjam/manifest.json, {name, engine} authoritative — written by morelli).
• scale:'device'→'css' normalized (no-op at CI's DSF=1).

1. Add the DISCORD_WEBHOOK_URL repo secret — until then everything is inert.
2. Calibrate: run the suite twice in CI, screenshots:noise the two dirs, set FLOORS in config.ts.
3. First re-baseline: promote a clean CI run's render, commit (expect a big, one-time chrome-font diff vs the Mac baselines).
4. Delete the old scripts/{compare,update-baseline}-screenshots.sh.
5. Once floors are proven stable, flip the gate to --fail-on-change.