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.
  • 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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