create/docs/ARCHITECTURE.md

Architecture

Bootstrap flow

FreeCAD startup
  └─ src/Mod/Create/Init.py
       └─ addon_loader.load_addons(gui=False)
            ├─ scan_addons("mods/")         — find package.xml manifests
            ├─ parse_manifest()             — extract <kindred> extensions
            ├─ validate_manifest()          — check min/max_create_version
            ├─ resolve_load_order()         — topological sort by <dependency>
            └─ for each addon in order:
                 ├─ add addon dir to sys.path
                 ├─ exec(Init.py)
                 └─ register in AddonRegistry (FreeCAD.KindredAddons)

  └─ src/Mod/Create/InitGui.py
       ├─ addon_loader.load_addons(gui=True)
       │    └─ for each addon in order:
       │         └─ exec(InitGui.py)
       │              ├─ sdk (priority 0):      logs "SDK loaded"
       │              ├─ solver (priority 10):  registers KindredSolverBackend
       │              ├─ gears (priority 40):   registers GearsWorkbench
       │              ├─ datums (priority 45):  registers Create_DatumCreator
       │              └─ silo (priority 60):    registers SiloWorkbench
       │                   └─ schedules deferred Silo setup (overlay, panels, observer)
       ├─ EditingContextResolver singleton created (MainWindow constructor)
       │    ├─ registers built-in contexts (PartDesign, Sketcher, Assembly, Spreadsheet)
       │    ├─ connects to signalInEdit/signalResetEdit/signalActiveDocument/signalActivateView
       │    └─ BreadcrumbToolBar connected to contextChanged signal
       └─ Deferred setup (QTimer):
            Create core (src/Mod/Create/InitGui.py):
            ├─  500ms: _register_kc_format()        → .kc file format
            └─ 10000ms: _check_for_updates()        → update checker (Gitea API)
            Silo addon (mods/silo/InitGui.py):
            ├─  500ms: kindred:// URL handler
            ├─  600ms: document observer (.kc tree building)
            ├─ 2000ms: auth dock panel (via kindred_sdk.register_dock_panel)
            ├─ 2500ms: Silo overlay registration     → "Silo Origin" toolbar overlay
            ├─ 3000ms: first-start settings check
            └─ 4000ms: activity dock panel (via kindred_sdk.register_dock_panel)

Addon lifecycle

Each addon in mods/ provides a package.xml manifest with a <kindred> extension block:

<kindred>
    <min_create_version>0.1.0</min_create_version>
    <load_priority>50</load_priority>
    <pure_python>true</pure_python>
    <dependencies>
        <dependency>sdk</dependency>
    </dependencies>
</kindred>

The loader (addon_loader.py) processes addons in this order:

1. Scan — find all mods/*/package.xml files
2. Parse — extract <kindred> metadata (version bounds, priority, dependencies)
3. Validate — reject addons incompatible with the current Create version
4. Resolve — topological sort by <dependency> declarations, breaking ties by <load_priority>
5. Load — execute Init.py (console) then InitGui.py (GUI) for each addon
6. Register — populate FreeCAD.KindredAddons registry with addon state

Current load order: sdk (0) → solver (10) → gears (40) → datums (45) → silo (60)

Key source layout

src/Mod/Create/              Kindred Create module
  ├── Init.py                Console bootstrap — loads addons via manifest-driven loader
  ├── InitGui.py             GUI bootstrap — loads addons, Silo integration, update checker
  ├── addon_loader.py        Manifest-driven addon loader with dependency resolution
  ├── kc_format.py           .kc file format round-trip preservation
  ├── version.py.in          CMake template → version.py (build-time)
  ├── update_checker.py      Checks Gitea releases API for updates
  ├── CreateGlobal.h         C++ export macros (CreateExport, CreateGuiExport)
  ├── App/                   C++ App library (CreateApp.so)
  │   ├── AppCreate.cpp      Module entry point — PyMOD_INIT_FUNC(CreateApp)
  │   └── AppCreatePy.cpp    Python module object (Py::ExtensionModule)
  └── Gui/                   C++ Gui library (CreateGui.so)
      ├── AppCreateGui.cpp   Module entry point — PyMOD_INIT_FUNC(CreateGui)
      └── AppCreateGuiPy.cpp Python module object (Py::ExtensionModule)

mods/sdk/                    [dir] Kindred addon SDK — stable API contract
  ├── package.xml            Manifest (priority 0, no dependencies)
  ├── kindred_sdk/
  │   ├── __init__.py        Public API re-exports
  │   ├── context.py         Editing context wrappers (register_context, register_overlay, ...)
  │   ├── theme.py           YAML-driven palette system (get_theme_tokens, load_palette, Palette)
  │   ├── origin.py          FileOrigin registration (register_origin, unregister_origin)
  │   ├── dock.py            Deferred dock panel helper (register_dock_panel)
  │   ├── compat.py          Version detection (create_version, freecad_version)
  │   └── palettes/
  │       └── catppuccin-mocha.yaml   26 colors + 14 semantic roles
  └── Init.py / InitGui.py   Minimal log messages

mods/gears/                  [submodule → gears.git] Gears workbench
  ├── package.xml            Manifest (priority 40, depends on sdk)
  └── ...                    Parametric gear generation

mods/solver/                 [submodule → solver.git] Solver addon
  └── ...                    Solver plugin support

mods/datums/                 [submodule → datums.git] Unified datum creator
  ├── package.xml            Manifest (priority 45, depends on sdk)
  ├── Init.py / InitGui.py   Bootstrap
  └── datums/                Python package (command, core, panel, detection, edit_panel)

mods/silo/                   [submodule → silo-mod.git] PLM workbench
  ├── package.xml            Manifest (priority 60, depends on sdk)
  ├── Init.py                sys.path setup for silo-client
  ├── InitGui.py             Consolidated GUI bootstrap (workbench, panels, observer, overlay)
  ├── silo-client/           [submodule → silo-client.git] shared API client
  │   └── silo_client/       SiloClient, SiloSettings, CATEGORY_NAMES
  └── freecad/               FreeCAD workbench (Python)
      ├── silo_commands.py   Commands + FreeCADSiloSettings adapter
      └── silo_origin.py     FileOrigin backend for Silo (via SDK)

src/Gui/SDK/                         KCSDK C++ shared library (libKCSDK.so)
  ├── KCSDKGlobal.h                  DLL export macros
  ├── Types.h                        Plain C++ types (ContextDef, DockArea, PanelPersistence)
  ├── IPanelProvider.h               Abstract dock panel interface
  ├── WidgetBridge.h/.cpp            PySide QWidget <-> C++ QWidget* (via Gui::PythonWrapper)
  ├── SDKRegistry.h/.cpp             Singleton registry — contexts, panels, providers
  └── bindings/                      pybind11 module (kcsdk.so)
      ├── kcsdk_py.cpp               Module definition — enums, functions, classes
      ├── PyIPanelProvider.h          Trampoline for Python subclassing
      └── PyProviderHolder.h         GIL-safe forwarding wrapper

src/Gui/EditingContext.h/.cpp        EditingContextResolver singleton + context registry
src/Gui/BreadcrumbToolBar.h/.cpp     Color-coded breadcrumb toolbar (Catppuccin Mocha)
src/Gui/FileOrigin.h/.cpp           FileOrigin base class + LocalFileOrigin
src/Gui/CommandOrigin.cpp            Origin_Commit/Pull/Push/Info/BOM commands
src/Gui/OriginManager.h/.cpp        Origin lifecycle management
src/Gui/OriginSelectorWidget.h/.cpp  UI for origin selection

src/Gui/Stylesheets/         QSS themes and SVG assets
src/Gui/PreferencePacks/     KindredCreate preference pack (cfg + build-time QSS)

See INTEGRATION_PLAN.md for architecture layers and phase status.