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[Feat] (MobileGL): full dual-source blending across state, transpiler, and both backends

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Wire GL_SRC1_* dual-source blend factors (glBlendFunc) end to end with the
glBindFragDataLocationIndexed color index, so a fragment shader can drive both
dual-source blend inputs.

State + converters:
  - RenderState BlendFactor gains Src1Color/OneMinusSrc1Color/Src1Alpha/
    OneMinusSrc1Alpha; GLToMG/MGToGL/MGToVk/MGToStr converters map them to
    GL_SRC1_*, VK_BLEND_FACTOR_SRC1_*, and readable names.

Transpiler layout(index = N):
  - ProgramAttrib carries explicitFragmentOutIndices; ProgramObject threads
    m_explicitFragDataIndex into it at both link sites.
  - TMglGlslIoResolver applies the color index as TQualifier.layoutIndex on the
    fragment output, emitting layout(index = 1) via the glslang Index decoration
    -> SPIRV-Cross path. Only the non-zero (dual-source) index is emitted: index 0
    is the GL default and an explicit "index = 0" would demand
    GL_EXT_blend_func_extended on GLES for ordinary single-source outputs.

Feature detection, POST, and hard-fail at use time (no silent fallback):
  - Vulkan: dualSrcBlend is detected at device creation and cached; a draw whose
    enabled blend state uses a SRC1 factor without the feature throws at pipeline
    build with the reason and a pointer to the POST row.
  - GLES: GL_EXT_blend_func_extended detected at load into
    GLESCapabilities.SupportsDualSourceBlend; a draw enabling blend with a SRC1
    factor without it throws in the blend-state sync with the same guidance.
  - DriverPost adds a dual-source-blend row for both backends (Pass/Warn).

Tests:
  - ProgramTest.CompileAndLinkWithExplicitFragmentOut now asserts the transpiled
    fragment shader carries layout(location = 0, index = 1) after a re-link with
    glBindFragDataLocationIndexed(index 1), and still omits any index qualifier
    for the plain index-0 output.
This commit is contained in:
swung0x48
2026-07-11 01:32:07 -04:00
parent e9fa99e16b
commit 0f99d93300
16 changed files with 154 additions and 4 deletions
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MobileGL/MG_Test/Program/ProgramTest.cpp
+19
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@@ -1399,6 +1399,25 @@ TEST_F(ProgramTest, CompileAndLinkWithExplicitFragmentOut) {
EXPECT_EQ(GetFragDataIndex(program, "fragColor"), 1);
EXPECT_EQ(GetFragDataIndex(program, "notAnActiveOutput"), -1);
// The color index must reach the transpiled shader as layout(location = 0, index = 1) so the
// driver binds fragColor as the second dual-source input; the SPIR-V Index decoration set from
// the glslang layoutIndex round-trips through SPIRV-Cross.
auto& spirvsIndexed = programObject->GetGeneratedSpirv();
auto& fragSpirvIndexed = spirvsIndexed[programObject->GetShaderIndexByStage(ShaderStage::Fragment)];
MG_Util::ShaderTranspiler::SpvcSession spvcSessionIndexed(fragSpirvIndexed,
MG_Util::ShaderTranspiler::SessionUsageBit::Transpile);
spvc_compiler_options optionsIndexed;
spvcSessionIndexed.CreateOptions(&optionsIndexed);
spvc_compiler_options_set_uint(optionsIndexed, SPVC_COMPILER_OPTION_GLSL_VERSION, 460);
spvc_compiler_options_set_bool(optionsIndexed, SPVC_COMPILER_OPTION_GLSL_ES, SPVC_FALSE);
spvcSessionIndexed.SetOptions(optionsIndexed);
const char* resultIndexed = nullptr;
spvcSessionIndexed.Compile(&resultIndexed);
printf("%s\n\n", resultIndexed);
const char* indexNeedle = "index = 1";
ASSERT_TRUE(strstr(resultIndexed, indexNeedle) != nullptr)
<< "Expected dual-source color index in generated shader.\n(Searching for \"" << indexNeedle << "\")";
// glBindFragDataLocation is equivalent to index 0 and resets it.
BindFragDataLocation(program, 0, "fragColor");
LinkProgram(program);