swayfx-mosaic/tooling/probes/step20c-presentation-identity/README.md

STEP20C presentation identity fixture — EXPERIMENTAL

The protocol precedes the private instrumentation. Only fixed two-output headless geometry HEADLESS-1 (-800,0) and HEADLESS-2 (0,0), both 800×600 at scale 1 and normal transform, is in scope. STEP20C remains NEXT and production multi-output Mosaic is NOT YET SUPPORTED.

The base is the published temporal fixture at Mosaic commit d19b15bfdeaa49ce81317c88a1baa250220a9998: pinned SwayFX fd71a6bdc061bd633b488ae7b83e8a6981d22f86, private Mosaic cd550382b311efdbfe3ed892f4e1d281d852e754, and private SceneFX 37ccd723bef49e6891156ffafce8f549f01446cc, plus the historical clip, popup guard and timing patches named in the temporal README. Installed wlroots 0.20.2 is audited against upstream tag commit d783533489e1f75d6886c2ab5c5960090ef268f8.

The new presentation-events.patch, SHA-256 dbf1f1d11c9c741b641916d25ac22bcb13c3455ee3002e1f534aa6794cd8a538, is applied only after the temporal private Mosaic patch in a disposable lab. It adds a listener to the private compositor's internal output object, logs native commit_seq and headless present event fields, and reads scene position and clip in the accepted commit callback. The listener is removed before output destruction. No public SceneFX ABI, headless backend, production build, cumulative patch or package is changed. Neither a commit callback nor a grim screenshot proves the pixels in a specific commit buffer. Logging may perturb timing.

Rebuild and replay

Requires the temporal fixture's Git/Meson/Ninja/C17, Wayland, Kitty, grim, wev, swaymsg and Pillow dependencies. Run from a full clone containing the pinned commits and this uncommitted phase-B fixture directory; when starting from published main, copy this directory into that clone first. The source manifest verifies the copied inputs. Preparation checks patch applicability with git apply --check, builds private SceneFX and Mosaic, compiles private C17 clients and prints the laboratory and build log. All runtime sockets are private; only the private compositor loads the private SceneFX library.

prep=$(sh tooling/probes/step20c-presentation-identity/prepare.sh)
printf '%s\n' "$prep"
LAB=$(printf '%s\n' "$prep" | sed -n 's/^LAB=//p')
(cd "$LAB" && sha256sum -c temporal-source-sha256.txt && \
    sha256sum -c presentation-source-sha256.txt)
PYTHONDONTWRITEBYTECODE=1 python tooling/probes/step20c-presentation-identity/run.py \
  "$LAB" private_mosaic identity
for mode in control private_standard private_mosaic; do
  PYTHONDONTWRITEBYTECODE=1 python tooling/probes/step20c-presentation-identity/run.py \
    "$LAB" "$mode" cycles --cycles 1
done
PYTHONDONTWRITEBYTECODE=1 python tooling/probes/step20c-presentation-identity/run.py \
  "$LAB" private_mosaic hidden_click
PYTHONDONTWRITEBYTECODE=1 python tooling/probes/step20c-presentation-identity/run.py \
  "$LAB" private_mosaic outside
PYTHONDONTWRITEBYTECODE=1 python tooling/probes/step20c-presentation-identity/analyze.py "$LAB"

The identity run creates A/B once with genuine button serials, executes five settled hide/return pairs and then twelve faster alternating requests. After the last return, it sends a fresh B button without closing or recreating either popup. cycles exercises explicit B then A closure; hidden_click and outside are separate grab-dismissal runs. The runner limits duration, captures and bytes, records exit codes, reaps only its own process groups, and removes only its private runtime. Do not use the daily Wayland or Sway IPC socket.

The negative-origin input fixture can also run b_cross for all three configurations and visible for private Mosaic in the prepared lab. These runs show pointer delivery at the clipped boundary, with their own analysis.json; they are not silently merged into the seven-run presentation summary.

for mode in control private_standard private_mosaic; do
  PYTHONDONTWRITEBYTECODE=1 python tooling/probes/step20c-negative-origin/run.py \
    "$LAB" "$mode" b_cross negative
done
PYTHONDONTWRITEBYTECODE=1 python tooling/probes/step20c-negative-origin/run.py \
  "$LAB" private_mosaic visible negative
PYTHONDONTWRITEBYTECODE=1 python tooling/probes/step20c-negative-origin/analyze.py "$LAB"

Correlation and retained evidence

LAB/presentation-results/ contains events.jsonl, commits.json, presentations.json, camera-states.json, damage-analysis.json, input-analysis.json, pixel-analysis.json, transitions.json, matrix.json and summary.json. The analyzer pairs only an actual native (output, commit_seq). The scene, owner and root-popup clip lines logged inside that synchronous commit callback are associated with that callback. It never assigns a grim PNG, pointer event or preceding damage extent to a commit without proof. PNG records contain monotonic capture bounds, output, SHA-256, fixed ROI and exact A/B color counts. Client event lines lack a common monotonic timestamp; this is an explicit input limitation.

The measured laboratory is /tmp/swayfx-mosaic-nested-grab-FQLULvot/. It retains a pilot identity run, the final identity run, five further presentation runs, four separate crossing/visible input controls, private builds and raw logs. The report records the limited PARTIALLY_FEASIBLE verdict. The source manifest is presentation-source-sha256.txt; the retained artifact manifest is presentation-artifacts-sha256.txt under presentation-results/.

Validation and cleanup

sh -n tooling/probes/step20c-presentation-identity/prepare.sh
PYTHONDONTWRITEBYTECODE=1 python -c 'import ast,pathlib; [ast.parse(p.read_text()) for p in pathlib.Path("tooling/probes/step20c-presentation-identity").glob("*.py")]'
meson test -C "$LAB/mosaic-build" --print-errorlogs
(cd "$LAB" && sha256sum -c presentation-source-sha256.txt)
git diff --check

Inspect exit-status.json, native event logs, XDG client traces, IPC trees, PNG hashes and matrix assertions before a verdict. Keep failed runs. If cleaning later, remove only the printed LAB and BUILD_LOG paths after preserving their evidence; never clean all /tmp or alter the daily session.