Unity UI framework FUI shifts object graph composition from runtime to compile time

FUI, a Unity UI framework, has evolved its code generation pipeline by moving UI composition steps from runtime to compile time using C# Roslyn Source Generators. Rather than scanning assemblies and resolving type relationships at runtime, the generator now emits binding factories and strongly typed routes so the Player runtime executes a pre-validated object graph. The approach eliminates a class of hard-to-detect bugs — such as missing unsubscribes or mismatched binding targets — that previously only surfaced when a specific screen was opened. An earlier prototype used an external FUICompiler executable, but it was discarded the same day it was created in favor of integrating directly into the Roslyn compilation pipeline. The shift to in-compilation generation allows SemanticModel and typed symbols to validate relationships at build time, surfacing errors as ordinary C# compiler messages rather than runtime failures.