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https://github.com/RetroPortingToolKit/psxrecomp
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Matthew Stanley
748e29f1b9
The 16:9 edge pop-in is the parallax 2D BACKDROP layer (ocean/cloud/mountain/
grass), drawn by overlay actor handlers (FUN_801216bc family) that compute
screenX = (worldX - camX) >> parallax in pure integer math and store it to the
object's +0x12 field WITHOUT the GTE — so the GTE X-squash that gives 3D the
wider 16:9 FOV never reaches them and far pieces sit past the 320px edge,
clipped (the blue void / half-rectangles at the edges). See TombaRecomp
ISSUES.md #8C for the full root-cause trail.
Fix = psx_ws_backdrop_x() (gpu.c): squash screenX around screen-centre by the
same ws factor as the GTE, identity at 4:3. Applied on BOTH execution paths
because overlay code runs interpreted when no cache DLL is loaded (the common
case in dev — see #8G):
- Native: recompiler emits write_half(.., psx_ws_backdrop_x(rt)) at the
[widescreen.backdrop] x_sites store (config_loader + code_generator +
main_psx --ws-config so the overlay compile gets the sites). Forwarded into
overlay DLLs via OverlayCallbacks {ws_backdrop_x, ws_x_margin, ws_sprite_tag}
(overlay ABI v2->v3 as the cache discriminator); compile_overlays.py glue +
--ws-config passthrough.
- Interp: dirty_ram_interp SH hook keyed by psx_ws_is_backdrop_site(pc); the
runtime registers the x_sites from game.toml (main.cpp).
Verified in data: backdrop slot screenX squashes 371 -> 318 (pulled on-screen).
PARTIAL: visible culling persists -> remaining cause is the backdrop spawn/
despawn window (separate from screenX clip); see #8C "REMAINING CAUSE".
Also added (earlier this session): ws_census draw ring, ws_margin override,
gpu_state ws fields.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>