Architecture Overview

Architecture Overview

Two native codebases share one design: a dependency-ordered core of pure geometry/IO logic with zero UI knowledge, wrapped by a platform-native UI. This keeps the unfold algorithm identical across platforms and independently testable.

For build commands and the project table, see the README; this page explains the shape of the code.

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Windows — layered .NET

Five projects in a strict one-way dependency chain. Domain has zero external dependencies.

flowchart LR
    Domain --> Geometry --> Application --> Infrastructure --> App

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Layer	Project	Responsibility	Key types
Domain	FourHUnfolder.Domain	Pure data model, no deps	Mesh, Face, Edge, UnfoldResult, AppSettings, FlapMode, FlapOverride
Geometry	FourHUnfolder.Geometry	The unfold pipeline	UnfoldEngine, KruskalMstBuilder, DualGraphBuilder, GlueTabGenerator
Application	FourHUnfolder.Application	Use-case services	MeshService, UnfoldService, ProjectSerializer, SettingsService
Infrastructure	FourHUnfolder.Infrastructure	File IO / export	ObjMeshLoader, PdoMeshLoader, AssimpMeshLoader, SvgExporter, PdfExporter
App (WPF)	FourHUnfolder.App	MVVM UI	MainViewModel, PatternCanvasControl, AssemblyViewModel, EditFlapsViewModel

No circular dependencies. UI (App) never reaches past Application into Geometry directly.

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macOS — shared core + SwiftUI app

Two Swift Package targets. The heavy lifting lives in a UI-free library that mirrors the Windows Domain+Geometry+Application+Infrastructure layers; the app target is thin SwiftUI.

flowchart LR
    Core["FourHUnfolderCore<br/>(pure Swift, no UI)"] --> App["FourHUnfolder<br/>(SwiftUI app)"]

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Target	Folder	Contents
FourHUnfolderCore	Core/	Algorithms, Graph, Math, Models
	IO/	Loaders (OBJ, PDO), Exporters (SVG, PDF)
	Services/	UnfoldService, ProjectSerializer
FourHUnfolder (app)	Models/, State/	AppState (ObservableObject), view models
	Views/	MainView, SceneKitView, PatternCanvasView, SidebarView

Keeping algorithms in FourHUnfolderCore means they're covered by XCTest without spinning up any UI — the same discipline as the Windows Geometry project.

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Why the split matters

• Testability — the unfold pipeline and IO are pure functions of their inputs; both platforms unit-test them directly (Windows xUnit, macOS XCTest).
• Parity — the unfold algorithm is implemented once per language against the same design, so results match.
• Portability of data — because state and serialization live in the core, the .4hu bundle is cross-platform.

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Rendering differs by platform

The only deliberately platform-specific area is rendering, mapped to each OS's native stack:

Concern	Windows	macOS
3D viewport	WPF 3D / DirectX	SceneKit (Metal)
2D canvas	WPF Canvas (PatternCanvasControl)	SwiftUI Canvas (PatternCanvasView)
PDF export	PdfExporter	Core Graphics
Extra mesh formats	Assimp (assimp.dll)	—