The publisher/dev splash logo's intro fade-IN was skipped: the logo
popped in at full brightness instead of ramping dim->bright like the
canary oracle. Root (measured, iterate-3AF/3AI): ours' guest vsync
counter is fed by a fixed-instruction-quantum proxy (one vsync per
150k retired instructions). During the ~1.1s splash asset-load the
title's frame pump runs ~10M instructions inside a single guest frame,
so the proxy fired ~66 vsyncs in that one frame. The pump's per-frame
delta (counter_now - counter_last) was therefore ~66 on the first tick,
which the anim tick (sub_823CDBF8) divides into the fade counter
[item+72] @ 0x40c0add0 -> the counter JUMPED 0->0x42(66) in one step,
landing past the fade-in region. Canary's wall-clock 60Hz vblank
advances ~1 per heavy load frame, so its counter ramps smoothly 0->66
and the fade-in renders.
Fix: anchor the lockstep vsync ticker to the guest's real present rate
(VdSwap count), mirroring real hardware where the title double-buffers
at vblank, so one heavy guest frame advances the vsync counter by ~1
instead of ~66.
- interrupts.rs: tick_vsync_instr now takes the live present count.
Two regimes: (1) bootstrap, before the guest's first present, keeps
the original fixed instruction quantum unchanged -- the iterate-2W
present-loop bootstrap needs vsyncs delivered BEFORE it can present
(measured: callback registered ~6M instr, first delivered vsync and
first present coincide; pure present-driven vsync would deadlock).
(2) present-anchored, after the first present: one vblank per present,
plus a small DRY_FALLBACK_CAP=4 instruction-quantum fallback per dry
window so a non-presenting frame still ticks a few vsyncs (a small
ramp like canary's 0/5/10/2/1...) without re-spiking to 66.
- handle.rs: cheap GpuBackend::swaps_seen() accessor.
- main.rs: pass the live present count into the lockstep ticker.
Not masking: the fade dt/counter is never clamped or synthesized; the
guest naturally computes a smooth dt once vblank tracks presents.
Verified:
- V1: fade counter 0x40c0add0 now ramps 0,6,8,10,12,13,+1... (was a
0->0x42 jump; direct baseline-vs-fix mem-watch).
- V2 (--ui readback via per-frame logo vertex-alpha): logo alpha ramps
102,136,204,221,238,254 (dim->bright fade-IN) vs baseline all 255
(pop-in). Real artwork (has_real_vertices) still renders; milestone-1
intact.
- V3: 150M boot progression intact -- texture_decodes=2, RTs=2,
tex_cache=1 unchanged; draws/swaps higher (tighter present loop),
1B sanity linear, no stall/collapse.
- V4: 50M --gpu-inline --stable-digest byte-identical 2x; golden
re-baselined intentionally (pacing-only delta: draws 718->1274,
swaps 147->259; structural fields unchanged). 688 tests green.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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