FX9 Pre-Parser & Preprocessor

Before any HLSL compiler sees the source, ShadowDusk runs two managed front-end passes. They live in ShadowDusk.HLSL (FxPreParser, FxFileParser) and ShadowDusk.Core/Preprocessor/.

FX9 Pre-Parser

.fx files contain D3DX FX9 / effect-framework blocks — technique, pass, sampler_state — that XNA and MonoGame inherited. These are not valid HLSL; DXC and vkd3d-shader cannot parse them. The pre-parser:

  1. Strips the FX9 blocks out of the source, leaving pure, compiler-safe HLSL (StrippedHLSL).
  2. Extracts metadata the compilers can't see: techniques, passes (with their VS/PS entry points and shader profile), sampler state, and render states.

It also performs targeted texture-keyword rewrites (e.g. legacy texture T; → Texture2D T;) so effect-syntax shaders compile faithfully on the modern toolchain.

The stripped HLSL feeds the compiler; the extracted metadata feeds the reflection and MGFX writer stages so the emitted .mgfx reconstructs the original technique/pass structure.

Preprocessor

The preprocessor (ShadowDusk.Core/Preprocessor/Preprocessor.cs) then:

  • Flattens #include directives, resolving them through an IIncludeResolver (file-system or in-memory). Missing includes fail loudly with SD0001; circular includes with SD0002.
  • Compares resolved include paths the way your storage spells them, not the way the operating system is assumed to. Deciding whether Shared/Common.fxh and shared/common.fxh are one file or two matters for #pragma once and for cycle detection, and inferring it from the OS is wrong on real targets: Android's file system is case-sensitive, and APFS can be formatted case-sensitive. An IIncludePathCanonicalizer is asked instead, so two spellings merge only when the storage confirms they name one file. An include that resolved only because your host ignores case gets the SD0008 warning, because that same shader fails with SD0001 on Android, Linux, or a case-sensitive Mac.
  • Injects platform macros so a single source compiles correctly per target:
Target Macros injected
DirectX HLSL=1, SM4=1, MGFX=1
OpenGL GLSL=1, OPENGL=1, MGFX=1

These mirror the macros mgfxc defines, so existing #ifdef-guarded shader source behaves identically.

Where this sits in the pipeline

These two passes are the first stages of The Faithful Pipeline: .fx → FX9 pre-parser → preprocessor → compiler (DXC for SPIR-V, or vkd3d-shader for DXBC).

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