Three defects in the 0.23.0 timeline presenter, all found while root-causing the
field report that turned out to be the slice wire. None of them is that bug; all
three are real, and the first is the one that would still bite once it is fixed.
The panel-period learner could only ever narrow. It is seeded from the display
mode Kotlin asked for — and `preferredDisplayModeId` is a REQUEST the system may
refuse (Smooth Display off, battery saver, thermal, an OEM governor). Ask for
120 Hz on a panel that stays at 60 and the presenter pins an 8.33 ms grid on a
16.67 ms display with no way back, for the rest of the session: it then aims at
instants that never arrive and releases faster than the panel scans. The learner
moves both ways now, and lives in `punktfunk_core::phase::PanelGrid` where it is
host-testable and where the iOS and desktop presenters can share it. The
asymmetry is kept and made explicit — narrowing is immediate (a finer real grid
is always safe to subdivide onto, and it is the per-uid down-rate case the seed
most often gets wrong), widening needs eight consecutive agreeing observations
and then takes the narrowest of them, because one wide sample is a missed
callback and eight in a row is a display that really did slow down.
The glass budget was a prediction with nothing underneath it. `OnFrameRendered`
already reports what actually reached glass, but the budget never consulted it,
so a wrong grid could hand SurfaceFlinger frames indefinitely: BufferQueue fills,
MediaCodec runs out of output buffers, the decoder stalls, and the no-output
backstop starts begging for keyframes. Releases are now counted against their
confirms and the presenter holds back past six outstanding — loose on purpose,
since the callbacks are allowed to arrive batched and a held frame in the
newest-wins slot is a dropped one. It self-clears when the confirms catch up, and
writes the ledger off after the same 100 ms the stale reopen uses, so a platform
that stops confirming can never wedge the stream. `qWait` and `unconfirmed` join
the 1 Hz pf.present line, which is what would have made this visible from a log.
The adaptive latch margin widened on `paced_drops` — the newest-wins store's own
policy evictions, which happen whenever the stream out-runs the panel and say
nothing about SurfaceFlinger's latch lead. On a healthy device that walked the
margin to its 2.5 ms ceiling and re-imposed the display latency the P2e sweep had
just measured away. It now widens on the measured latch exceeding one panel
period plus the live margin, which is what a missed vsync actually looks like.
Also corrects two doc comments that named `display.refreshRate` as the panel_hz
source; it has been the mode table since the A024 down-rate fix.
Gates: 278 punktfunk-core lib tests (7 new PanelGrid cases incl. the refused-mode
regression), clippy -D warnings and fmt clean, cargo ndk check green on arm64 and
armv7. Android clippy reports the same 4 warnings as the base commit and no new
ones. NOT yet confirmed on glass.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
enricobuehlerandClaude Opus 5
20de58a78a