The engine synthesized an eglSwapBuffers on each detected frame boundary.
That duplicated the present Android's GLSurfaceView already performs after
every onDrawFrame return, so every frame reached the screen twice - the
second time from a buffer still holding the PREVIOUS frame.
The whole mechanism rested on a premise recorded 2026-09-18 and never
verified live: that nativeOnResume runs the guest's persistent loop on the
GLThread and never returns, leaving the framework unable to present. An
entry/exit counter added to GameRenderer.onDrawFrame shows that is false -
it returns every frame (entries=698 exits=697, the gap being the call in
flight). Rates match 1:1:
synthetic swaps 12.98/s (SWAPMARK, one line per swap)
onDrawFrame 12.69/s (so the framework swapped 12.69/s too)
The user saw this as the car jumping forward then back along its path.
Frame-by-frame the race clock stepped 1:10.06 -> 1:10.03 -> 1:10.09 ->
1:10.06, with presents arriving in pairs 10-20ms apart at a 218ms period -
exactly the synthetic swap period.
Letting the framework present is also what the real game does: libapp.so
cannot present at all (only EGL import is eglGetProcAddress; the string
"eglSwapBuffers" is absent from the binary), and on the A9 all 2,736
eglSwapBuffers calls in 46s came from Android's own framework.
Measured after, on the Pixel 6a:
frame interval median 89ms -> 17ms
p90 217ms -> 19ms
max 316ms -> 24ms
synthetic swaps 0 (verified, not merely absent from view)
onDrawFrame 12.69 -> 12.39/s (throughput deliberately unchanged)
User verdict: "Сейчас очень плавно". Throughput is untouched - this fixes
presentation, not the ~7x simulation deficit.
Kept behind kSynthesizeSwap rather than deleted: the 2026-09-18 symptom it
was built for (screen cycling between stale loading screen, black, and the
real scene) was diagnosed under the false premise above, so its actual
cause is still open.
Co-Authored-By: Claude <noreply@anthropic.com>
Fixes the synthetic car_select jump for cold sessions, makes the loadout
exit chain safe for real (non-synthetic) events, and adds a native->Kotlin
GameEvents bridge (onMapLoaded/onRaceStarted/onRaceEnded/onUpgradesAccepted/
onCarSelected) so both the UI layer and a future native RatNet client can
learn what the player picked - car id, accepted upgrades, and paint color
(name + RGBA) are all resolved live from the game's own engine state
rather than a static extracted table, so they stay correct for any car
added later. Includes a Jetpack Compose overlay as a worked example of a
UI-side GameEventListener consumer.
Full investigation history, root causes, and the several dead ends ruled
out along the way are documented in PROGRESS.md (cont. 30-63b).
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
megboyzzandClaude