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[Fix, Test] (DirectGLES, PixelStoreProcessor, MG_IntegrationTest): read a packed level's stored words instead of trusting the shadow

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swung0x48
2026-08-20 16:15:52 -04:00
parent 6ea4f32635
commit 48a70fea81
4 changed files with 420 additions and 14 deletions
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MobileGL/MG_Util/Texture/PixelStoreProcessor.h
+11 -5
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@@ -47,12 +47,18 @@ namespace MobileGL::MG_Util::PixelStoreProcessor {
// True when a packed internal format has REDUNDANT encodings, so decoding a texel and
// re-encoding it keeps the VALUE but not the BITS. Only RGB9_E5 does: its shared exponent can
// be lowered with the mantissas shifted up to match, and the spec's encoder always emits the
// canonical form. RGB10_A2, RGB10_A2UI and R11F_G11F_B10F round-trip through float32
// bit-exactly, so a GPU readback can answer for them.
// canonical form, so no readback that goes through a decode cycle can return the stored words.
//
// This is what decides whether the CPU shadow has to stay authoritative for a format: a
// readback of an RGB9_E5 level through a colour attachment cannot return the stored words, no
// matter how well behaved the driver is.
// Read this as "a FINITE value re-encodes to different bits", and nothing wider. This comment
// used to assert that RGB10_A2, RGB10_A2UI and R11F_G11F_B10F "round-trip through float32
// bit-exactly, so a GPU readback can answer for them", and that is false for
// R11F_G11F_B10F: a field whose 5-bit exponent is all ones is an Inf or a NaN, and a NaN's
// payload does not survive the trip (EncodeFloatToUnsignedSmallFloat re-encodes every NaN as
// the canonical payload 1). glCopyImageSubData from an RGB9_E5 source produces exactly such a
// word in the blue field on every texel, because the source's shared-exponent field is all
// ones. The bit-exact answer for all four formats is the raw-word route,
// DirectGLES::ReadPackedLevelWordsViaScratch; this predicate only picks which of the older
// fallbacks to prefer when that route is unavailable.
Bool HasRedundantPackedEncoding(TextureInternalFormat internalFormat);
// Decodes the canonical shadow-mip storage of `internalFormat` into wide RGBA texels for CPU