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[Feat] (MG_Backend/DirectGLES): packed-type readback encoding - repack wide RGBA reads into all GL 3.3 packed pixel types (3_3_2/2_3_3_REV, 5_6_5(_REV), 4_4_4_4(_REV), 5_5_5_1/1_5_5_5_REV, 8_8_8_8(_REV), 10_10_10_2/2_10_10_10_REV, packed-float 10F_11F_11F_REV and shared-exponent 5_9_9_9_REV) for ReadPixels/GetTexImage; conversion helpers extracted to context-free ReadbackImpl (Utils.cpp) with unit tests asserting exact packed words against the GL CTS pack_* oracle layouts

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swung0x48
2026-07-16 11:08:02 -04:00
parent 1cefb9780b
commit 0005a50517
4 changed files with 621 additions and 232 deletions
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MobileGL/MG_Backend/DirectGLES/Utils.h
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@@ -45,6 +45,51 @@ namespace MobileGL::MG_Backend::DirectGLES {
namespace FramebufferImpl {} // namespace FramebufferImpl
// Pure CPU helpers of the client-format readback conversion (ReadPixels/GetTexImage repack a wide
// RGBA(_INTEGER) read into the caller's (format, type) layout). Kept context-free so unit tests can
// exercise the exact packing the GL CTS packed_pixels oracle compares against.
namespace ReadbackImpl {
struct ReadbackChannelMapping {
Int sourceChannel[4]; // RGBA source channel feeding each destination component
Int channelCount; // destination component count
Bool isInteger;
};
Bool GetReadbackChannelMapping(GLenum format, ReadbackChannelMapping& outMapping);
// Byte size of one destination component of `type`; packed types report the packed word size.
// 0 = type not supported by the conversion path.
SizeT GetReadbackComponentSize(GLenum type);
// Bit-field layout of a GL packed pixel type. width/shift are indexed in the client format's
// component order (matching ReadbackChannelMapping); shift is the LSB position of the field in
// the packed word: non-REV types pack the first component from the MSB, *_REV types from the
// LSB (GL 3.3 table 3.6; field positions mirror the GL CTS glcPackedPixelsTests pack_* oracle).
struct PackedReadbackLayout {
Int fieldCount; // format components stored in the packed word
Int width[4]; // bit width of each component's field
Int shift[4]; // LSB bit position of each component's field
SizeT byteSize; // packed word size in bytes (1, 2 or 4)
Bool isFloatPacked; // 10F_11F_11F_REV / 5_9_9_9_REV: fields hold unsigned small floats
};
Bool GetPackedReadbackLayout(GLenum type, PackedReadbackLayout& out);
// Unsigned small-float encoders (EXT_packed_float / EXT_texture_shared_exponent semantics).
Uint32 EncodeFloatToUnsignedF11(Float value);
Uint32 EncodeFloatToUnsignedF10(Float value);
Uint32 EncodeSharedExponentRGB9E5(const Float rgb[3]);
// Destination bytes per pixel for a (format mapping, type) readback pair; 0 when the pair is
// not convertible (unknown type, packed field count != format component count, floating-point
// or packed-float type with an integer format).
SizeT GetReadbackDstPixelSize(const ReadbackChannelMapping& mapping, GLenum type);
// Repacks one row of wide RGBA(_INTEGER) texels (4 components of wideType each) into the
// client's (format, type) layout. src holds width * 4 * GetReadbackComponentSize(wideType)
// bytes, dst receives width * GetReadbackDstPixelSize(mapping, type) bytes.
void ConvertWideReadbackRow(const Uint8* src, Uint8* dst, SizeT width, GLenum wideType,
const ReadbackChannelMapping& mapping, GLenum type);
} // namespace ReadbackImpl
namespace PrgramImpl {
String ProcessOutColorLocations(const String& glslCode);
String ForceSupporterOutput(const String& glslCode);