Task 18. Cancellation now PARKS the record instead of returning it into
a context that drops it: two of the three cancellation sites --- the
mapping-generation advance and publish_absent_panel --- run inside frame
production, where no target effect can happen, so the gesture ended with
the child still holding its button.
A SLOT, not a queue. The latch holds at most one gesture per frontend,
so at most one release can be owed, and the bound is structural rather
than a cap someone chose. Overwriting a still-parked release is a
debug_assert rather than a silent loss --- a backstop, since the ordering
is what actually prevents it.
Three drains, each against a specific way the release would otherwise
arrive too late or not at all: before any subsequent panel-pointer
effect, before detach teardown (the next statement in that arm drops the
state holding the record), and at the projection seam between
render_frame returning and its messages being written.
Q1, Q2, Q3, Q4 and Q6, each biting its named mutation with the run
counts checked. The mutations discriminate: dropping the park fails all
three delivery rows; removing the effect-drain spares Q4, which has its
own; removing the detach drain hits Q4 alone. Q3 asserts ORDER rather
than arrival, and the mutation that keeps the drain but moves it after
the press effect fails exactly that assertion, with the child's stream
coming back press-then-release.
Q5 IS OWED, AND RECORDED AS SUCH. The projection-seam drain needs a row
that drives the real per-frontend frame loop; these rows call
render_frame directly and never enter it. The seam still matters --- a
cancellation with no following panel event and no detach would let the
successor frame overtake the release its own new mapping required --- so
it is written down as unwitnessed rather than treated as covered by its
neighbours.
Two fixture facts worth keeping: the Q rows cancel through Absence
rather than a mapping advance, because a terminal panel's key tracks its
screen and anchor, not its buffer, so a foreign edit does not move it;
and the helper re-shows AND re-declares the panel, because a panel left
Absent fails the inbound ladder and the row would then be observing the
ladder rather than the slot.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016bqGA6s9tTUFzYpbeW3tai
Levi Neuwirth
ab8ddaecec