TriggerEngine::CheckSample returned early in every state but ARMED, so an
edge arriving while a capture was being collected or handed out was
dropped, and the automatic rearm then waited for a FRESH edge. The engine
was therefore blind from its own trigger point until the capture had been
harvested — a post-window — and for the holdoff on top of that.
On a sparse pulse train that rounds the capture spacing up to a whole
pulse period: at the default 1 s window the blind stretch is 1 s, so a
1 Hz train was caught at 0.5 Hz and a wider window lost whole multiples.
The comparator now keeps running through COLLECTING and TRIGGERED and
remembers the first edge at or past trigTime + max(postSec, holdoffSec).
The holdoff guards against re-triggering on the ringing of the same
event and is measured from the trigger point, so it overlaps the
post-window rather than adding to it. Rearm() fires on the remembered
edge; it also keeps the tracked level, so the first sample after it has
a real predecessor instead of being spent seeding one.
Arm() stays the operator's arm and discards the held edge — they asked
for the next event, not one already been and gone — and SetConfig() and
Disarm() drop it too, since it was never judged against the new window.
This is the same defect and the same remedy already validated in the Go
hub (wshub/trigger.go, trigger_sporadic_test.go); the C++ hub had been
left with the original semantics.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
