8K is 18x at a 240-line reference, and a full-VRAM surface at 18x is
18432 px wide: over the 16384 limit of Apple's GL, Intel and MoltenVK. A
title only needs its displayed frame at 18x, so past the full-VRAM limit
the GL backend now splits the work:
- The authoritative VRAM stays the ordinary hr surface at 1x, i.e. the
native renderer unchanged: pack, CPU readback, render-to-texture and VRAM
copies are exactly the native results (s_hr_scale; s_scale stays the
presented scale gr_scale reports).
- A presentation-only surface at S covers the displayed columns W =
[x0, x1) x all 512 rows (R4: 0..319, 5760x9216 at 18x, 405 MiB). Every
GPU write touching W is mirrored into it: textured and flat batches,
lines (quads), fills, uploads, the depth24 clear, and VRAM copies (hi to
hi when the source is in W, otherwise the 1x source upscaled; both staged
before drawing so overlapping copies read pre-copy pixels). It keeps its
own stencil. A separate blit program carries the window projection, so
the canonical shaders are untouched.
- W grows (64-column aligned) the first time a display rectangle outside it
is presented, seeded by upscaling the 1x content. Present, hold-last,
interpolation capture, screenshot_hires and the native-wide centre read
it; a display it cannot hold presents at 1x.
It engages only when the full-VRAM surface cannot hold the request (driver
limit or budget), sized so a 320-wide window fits both; up to 16x on the
M4 nothing changes. PSX_GL_HIRES_WINDOW=0/1 disables or forces it. The
launcher note and video_info (hr_scale, windowed, hires_window_*, hires_fbo)
report it.
Default-off: at 1x and whenever the full-VRAM surface fits, the paths are
the previous ones (same native-VRAM and present digests on a fixed scene at
1x and 2x).
Tests: gl_scale_invariance_test now also forces the window at 2/3/5/9x and
requires its frame at internal resolution to be byte-identical to the
full-VRAM surface at the same scale (copies inside, into and across the
window edge, fills/uploads across it, mask, all blend modes) with native
VRAM identical to 1x, and runs it at 18x; gl_scale_limits_test covers the
window clamp; guards pin that it only engages past the full-VRAM limit.
Verified in R4 on an M4: the 8K preset renders 5760x4320 in a race (rear-
view mirror present) and 5760x8640 on a 480i menu.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Shokunin
2211ecabf3