swayfx-mosaic/tooling/probes/step20c-applied-state-input/README.md

STEP20C applied state / input fixture — EXPERIMENTAL

The protocol was written before this fixture. This directory will retain only source patches, preparation, runner and analysis code needed to reconstruct a disposable private headless laboratory. Its inputs are the frozen buffer fixture, not production Mosaic or installed SceneFX. Generated builds, buffers, PNGs, logs, sockets and manifests remain in a named private /tmp laboratory.

Status: EXPERIMENTAL / PARTIALLY_FEASIBLE. The distinct applied-state-input.patch applies after the frozen buffer patch and changes only private output.c, transaction.c, cursor.c and seat.c. It leaves clipping and hit decisions untouched. The patch's SHA-256 is 8a0766536fa728a6be6ef29aea3be67abbfad107f2fcd6048718097499a4d88f.

Rebuild and bounded replay

prep=$(sh tooling/probes/step20c-applied-state-input/prepare.sh)
printf '%s\n' "$prep"
LAB=$(printf '%s\n' "$prep" | sed -n 's/^LAB=//p')
(cd "$LAB" && sha256sum -c asi-source-sha256.txt)
PYTHONDONTWRITEBYTECODE=1 python tooling/probes/step20c-applied-state-input/run.py \
  "$LAB" private_mosaic buffer_cycles --cycles 3 --asi-mode 0 \
  --max-seconds 120 --max-captures 100
PYTHONDONTWRITEBYTECODE=1 python tooling/probes/step20c-applied-state-input/run.py \
  "$LAB" private_mosaic buffer_cycles --cycles 3 --asi-mode 1 \
  --max-seconds 120 --max-captures 100
PYTHONDONTWRITEBYTECODE=1 python tooling/probes/step20c-applied-state-input/run.py \
  "$LAB" private_mosaic buffer_cycles --cycles 3 --asi-mode 2 \
  --max-seconds 120 --max-captures 100

Mode 0 logs without a probe lock/read. Mode 1 samples only three buffers after both A/B have mapped, in order visible 400, hidden 1280, returned 400. Mode 2 reads these again only during their matching headless present while the owned reference remains. The runner creates a private runtime, Wayland display and IPC socket, bounds captures, then stops its process groups. Standard and pointer controls reuse the frozen negative-origin runner against the same private binary, with scenario visible, b_cross or hidden_click and geometry negative. Use analyze.py LAB RUN for each run; outputs go to LAB/results-asi/RUN/.

For controlled lifetime paths, run one pair with mode 1 and --test-hold: the first already-presented buffer stays held until a subsequent real HEADLESS-1 buffer commit. Use --test-timeout instead to pause 2.3 seconds and observe the two-second post-commit timer. These switches are private fault injections; normal mode does neither. Rejected commits and output destruction were not injected in the measured campaign.

Interpretation

asi_applied_epoch is an experimental counter incremented after private popup position/clip arrangement and after a transaction's root arrangement. It can increment even if the sampled state does not change and misses direct client-buffer, effect, animation, damage, output and other SceneFX mutations. Matching values show only that these instrumented sites did not run between observations; they are not a native atomic scene/input generation. ASI_HIT records the executed scene node-at result; ASI_DELIVERY records the seat's focused surface before wlroots button notification. XDG grabs may alter delivery, so the client log is the separate final observation. No input event is assigned a frame ID.

The selected source buffer is GBM XB24. The successful read path uses FX texture readback to XRGB8888; it can synchronize GPU/CPU. Each selected copy is 1,920,000 bytes. The private hold is keyed by output and native commit sequence. HEADLESS-2 repaint cannot release a HEADLESS-1 hold; configuration-only commits do not replace it. The one-slot-per-output model releases on matching present, accepted same-output replacement, timeout or output destruction. Its two-second timer begins after readback and commit; it cannot bound a stalled GPU readback call.

Measured lab

/tmp/swayfx-mosaic-nested-grab-l2HvAkRe/ contains trace-only, three- buffer selective and second-read modes, one-pair replacement and timeout injections, three Mosaic pointer scenarios and two splith controls. The report records exact runs, counts, hashes, limits and status. Generated evidence is outside Git. STEP20C stays NEXT; multi-output Mosaic remains NOT YET SUPPORTED.