Vegas logged an FPS line at INFO every five seconds for the whole of
every run. Measured over two hours on a rig: 1410 samples, 98.5% of them
within 10% of target. The 1.5% that were not included a reading of
8.6fps against a target of 60 -- a real stall, completely invisible
inside 1389 lines reading "59.6". INFO is now reserved for a shortfall,
the recovery from one, and a slow heartbeat so a healthy marquee still
shows a pulse. Scroll-progress tracing drops to DEBUG for the same
reason: it runs for the whole of every scroll and is what you turn debug
on to watch.
Three review findings, all fixed here.
1. Per-frame timing used the wall clock (critical). The loop sleeps the
remainder of each frame budget:
frame_elapsed = <now> - frame_started
time.sleep(max(0.0, frame_interval - frame_elapsed))
These devices have no RTC, so the clock jumps by however wrong boot
time was when NTP first syncs. A backward step makes frame_elapsed
negative, `frame_interval - frame_elapsed` then exceeds the whole
budget, and the render loop stalls for the size of the correction. A
forward step instead inflates the p99 and worst-frame figures this
telemetry exists to report. Both per-frame timestamps are monotonic
now. start_time stays wall-clock: it is only used for the iteration
duration report, where a human-readable clock is the point.
2. FPS health state reset every iteration. last_fps_health_log and
was_degraded were locals of run_iteration(), which is called once per
cycle. Starting at 0.0 against a monotonic clock, `due` was true on
the first sample of every iteration, so the 300s heartbeat degenerated
into one report per cycle -- reintroducing the noise this change is
about. A recovery that crossed an iteration boundary was never
reported either, since was_degraded had already gone back to False.
Both now live on the coordinator and reset in start().
3. The degraded threshold read as an off-by-one. 90% of target is
deliberate -- a marquee jitters constantly, so "anything below target"
would report forever and mean nothing -- but nothing said so, leaving
55fps-against-60 looking like a missed case. The constant now states
the band and gives that exact example.
Also drops two soccer logo PNGs that a `git add -A` had swept into the
first commit. They are unreferenced, unrelated to frame-rate telemetry,
and 210KB.
Verified: each fix mutation-checked -- restoring the wall clock on either
per-frame timestamp, or making the health state local again, fails the
new tests. 566 passed across the vegas, coordinator and scroll suites.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01STMbQE4YctTacQXfbYqKuW
