Glue Project Codegen

Glue Project JSON → Generated Code

File formats

.glux→.gluj and the later per-element split into .glsj/.glej are both GluxVersions-gated migrations — see the gluj-versions skill for the version enum and gating workflow; don't duplicate that history here.

Load entry point: GlueProjectSaveExtensions.Load in FRBDK/Glue/Glue/SaveClasses/GlueProjectSaveExtensions.cs — prefers .gluj over .glux if both exist, falls back to .glux if no .gluj (mid-migration tolerance), then loads per-element .glsj/.glej files individually if FileVersion >= SeparateJsonFilesForElements. Save entry point: SaveMainAndElementsToFile (same file) → RemoveAndSaveElements for per-element files. Both driven from FRBDK/Glue/Glue/IO/ProjectLoader.cs and GluxCommands.SaveProjectAndElements*.

Schema is a plain POCO graph, not a .schema.json — the canonical source is FRBDK/Glue/GlueCommon/SaveClasses/ (GlueProjectSave.cs, ScreenSave.cs, EntitySave.cs, GlueElement.cs, NamedObjectSave.cs, CustomVariable.cs, StateSave.cs, ReferencedFileSave.cs, PropertySave.cs, VariableDefinition.cs). A second, trimmed copy of GlueProjectSave/GluxVersions lives at FRBDK/Glue/GameCommunicationPlugin/GlueControl/Embedded/Models/GlueProjectSave.cs, compiled as source into the user's game for live in-editor editing — it's frozen at an old version and drifts from the editor's own enum; don't assume version parity between the two when touching live-edit/hot-reload code.

Serialization gotchas (landmines)

• PropertySave.Value boxes as long/double, not int/float. Newtonsoft deserializes bare JSON numbers that way. Always read through PropertySaveListExtensions.GetValue<T> (PropertySave.cs), which special-cases the conversions — reading .Value directly and casting will throw or silently misbehave.
• Enums serialize as raw ints — no StringEnumConverter anywhere in the save classes. Hand-editing a .gluj requires knowing the enum's underlying int value.
• NullValueHandling/DefaultValueHandling differ between the main file and per-element files. Main .gluj: NullValueHandling.Ignore + DefaultValueHandling.IgnoreAndPopulate. Per-element .glsj/.glej: DefaultValueHandling.Ignore only. Both live in GlueProjectSaveExtensions.cs.
• New properties on save classes must default to the type's own default value, never a custom default — a comment at GlueProjectSave.cs states this explicitly, since IgnoreAndPopulate means the JSON omits anything at default and repopulates it on load. Giving a property a non-standard default silently breaks backward compatibility for every existing project file.
• Per-element load tolerates a corrupt file: a null/failed ScreenSave/EntitySave deserialize is skipped rather than aborting the whole project load, so a single bad .glsj/.glej merge doesn't brick the project.
• GlueSettingsSave (user app settings, not project data) intentionally never finished migrating to JSON — still XML, with a commented-out JsonConvert call and a note that build tool associations broke under JSON (suspected TypeConverter interaction). Don't "fix" this without digging into that history first.
• Saves call FileWatchManager.IgnoreNextChangeOnFile(...) before writing to suppress self-triggered reload — general mechanism covered by the glue-file-watch skill.

JSON → generated code pipeline

Entry points: CodeWriter.GenerateCode(GlueElement element) (FRBDK/Glue/Glue/CodeGeneration/CodeWriter.cs) builds one Screen/Entity's <ElementName>.Generated.cs; CodeGeneratorIElement.cs wraps it (GenerateElementAndDerivedCode also regenerates inheriting elements); GenerateCodeCommands (Glue/Plugins/ExportedImplementations/CommandInterfaces/GenerateCodeCommands.cs) is the public command surface, including GenerateAllCode for full-project regen.

Generation is a plugin pipeline, not one big method: each contributor subclasses ElementComponentCodeGenerator (CodeGeneration/ElementComponentCodeGenerator.cs), overriding phase methods (GenerateFields, GenerateConstructor, GenerateInitialize, GenerateAddToManagers, GenerateActivity, GenerateDestroy, GenerateEvent, HandlesVariable, …). CodeWriter's static ctor lists the built-ins in order (fields → static ctor → ctor → Initialize → AddToManagers → Activity → Destroy → additional methods): ErrorCheckingCodeGenerator, ScrollableListCodeGenerator, StateCodeGenerator, FactoryElementGeneratorEarly, FactoryElementCodeGenerator, ReferencedFileSaveCodeGenerator, NamedObjectSaveCodeGenerator, CustomVariableCodeGenerator, EventCodeGenerator, PooledCodeGenerator, IVisibleCodeGenerator, IWindowCodeGenerator, ITiledTileMetadataCodeGenerator, PauseCodeGenerator, LoadingScreenCodeGenerator. External plugins (Gum, TopDown, Platformer, RedGrin, …) contribute their own generators via ICodeGeneratorPlugin (Glue/Plugins/Interfaces/ICodeGeneratorPlugin.cs) — currently only its GenerateActivity/GenerateAdditionalMethods hooks are wired up (there's a //TODO: Add more generation types here marking the gap).

The two save-class types that map most directly to generated members:

• NamedObjectSave (instance placed in a Screen/Entity) → NamedObjectSaveCodeGenerator.cs: field + constructor/Initialize instantiation + AddToManagers wiring. CodeGenerationType (Full vs OnlyContainedObjects vs Nothing) controls whether a field is generated fresh or the object is assumed already declared by an inherited base — get this wrong in a custom generator and you get duplicate-field build errors.
• CustomVariable (exposed/tunneled variable) → CustomVariableCodeGenerator.cs: either a new C# property or a tunneled property forwarding to a NamedObjectSave member. Base-class variables are not regenerated in derived elements unless tunneling, shared, or creating an event — overriding that precedence incorrectly silently drops the override.

Regeneration is synchronous-on-edit, not file-watch or debounce driven: nearly every mutating Glue command (add/remove/rename object, variable, screen, entity, event) calls GlueCommands.Self.GenerateCodeCommands.GenerateElementCode(element) directly, queued onto TaskManager.Self to run off the UI thread in order. GenerateAllCode additionally fires on project load and via an explicit "Regenerate All Code" command.

Other gotchas:

• EntireClassCodeGenerator is [Obsolete] — use FullFileCodeGenerator (Glue/Plugins/CodeGenerators/FullFileCodeGenerator.cs) for new standalone-file generators.
• Generators never emit using statements — deliberate, since multiple plugins' generators could pick conflicting types for the same short name. Use fully-qualified names in generated code.
• The hand-written half of a Screen/Entity (CustomInitialize, CustomActivity, CustomDestroy, CustomLoadStaticContent) lives in a sibling non-.Generated.cs partial seeded from CodeWriter.ScreenTemplateCode/EntityTemplateCode — the .Generated.cs partial calls into these at fixed points.

Runtime-testing generated code

Compiling generated code proves it resolves against the engine, not that its logic is correct. To pin runtime behavior, build a gold project, Assembly.LoadFrom its output DLL, and reflect into the generated type — see GoldProjectCompileTests.FormsSampleProject_WithAddedPlatformerEntity_LoadInGlue_ThenBuild_ShouldSucceed.

Landmines: constructing an entity needs FlatRedBall.FlatRedBallServices.InitializeCommandLine() first (reflectively) or LoadStaticContent NREs; the parameterless ctor reads ScreenManager.CurrentScreen (null headless) — use the (contentManagerName, addToManagers: false) overload; a CSV-generated custom class emits public fields, not properties.

A tile map's data needs no GraphicsDevice: TiledMapSave.FromFile plus ReducedTileMapInfo.FromTiledMapSave yield layer names, map dimensions, per-layer tileset image paths and every tile position headlessly. Only LayeredTileMap's per-layer texture load (TextureContentLoader.LoadTexture2D, which throws when Renderer.Graphics is null) needs one — assert on the reduced info when a test cares which map loaded rather than how it rasterizes.

Related skills

• gluj-versions — the GluxVersions enum, FileVersion gating, and the version-bump checklist. This skill assumes that context; don't restate it here.
• gum-codegen — Gum standard-runtime (NineSlice/Text/Container/…) property and state codegen specifically. Separate pipeline from the general ElementComponentCodeGenerator list above.
• glue-file-watch — the general external-change-detection and self-save-suppression mechanism referenced above.
• glue-project-types — everything above is FRB1's mandatory pipeline. FRB2 projects generate nothing by default and, when opted in, use a separate generator that never goes through CodeWriter.