Shader Generation

Raster checks generated shader and package files into the repository because several build systems consume the same shader interfaces in different ways. Canonical sources live in Frameworks/Raster/Shaders. Generators write the repetitive blend code, host encoders, umbrella headers, SwiftPM symlinks, and the embedded source library that SwiftPM builds compile.

Generator sequence

1. Boilerplate generator writes blend shaders, multilayer blend shaders, custom blend wrappers, MTIVector SIMD helpers, and the Swift SIMD argument encoder.
2. Umbrella-header generator discovers public headers and rewrites the framework umbrella header while excluding private implementation headers.
3. Swift package generator recreates Sources/, links canonical Swift/Objective-C files into target-shaped directories, writes the module map, creates both flat and namespaced public header links, and embeds the built-in Metal source.

The deterministic commands are:

swift run --package-path Utilities main boilerplate-generator "$PWD"
swift run --package-path Utilities main umbrella-header-generator "$PWD"
swift run --package-path Utilities main swift-package-generator "$PWD"

utilities.sh is the interactive wrapper for local use, while CI and release scripts call the deterministic commands.

The embedded library

The package still has a historical source-embedding path for the built-in Metal library. The Swift package generator concatenates MTIShaderLib.h, function constants, and every sorted .metal source file, strips local include directives, and writes the concatenated result into MTISwiftPMBuiltinLibrarySupport.mm. At runtime the context registers that source and compiles a device library with fast math enabled. A shader change can pass a framework project build and still fail for a SwiftPM consumer, because the checked-in embedded source may still be yesterday's file.

Custom blend arity

Built-in wrappers call headroom-aware overloads. Custom formula wrappers keep calling the consumer's two-argument blend(backdrop, source) function. The generator makes that split. Hand-editing the generated .metal output repairs one checkout and loses the fix on the next pass.

Idempotence

When checked-in outputs are already current, a clean generator pass produces no diff, and a second complete pass is byte-identical to the first, including symlink destinations and generated source. The release gate checks tracked changes and untracked outputs, because git diff alone cannot see a newly generated missing file.

Source

Frameworks/Raster/Shaders/MTIShaderLib.h                   Canonical shader interface
Frameworks/Raster/Shaders/*.metal                         Canonical shader implementations
Utilities/Sources/BoilerplateGenerator/                       Repetitive shader and encoder output
Utilities/Sources/UmbrellaHeaderGenerator/                    Public header aggregation
Utilities/Sources/SwiftPackageGenerator/                      Package layout and embedded library
Sources/RasterObjectiveC/MTISwiftPMBuiltinLibrarySupport.mm Generated SwiftPM source blob
test.sh                                                       Two-pass drift gate