Launch

Design Intuition is a 3D editor. Launch creates the Graph component, which sets up a 3D canvas and populates it with Smart Objects (SO).

Launch details

Graph.svelte mounts, sizes the canvas, calls engine.setup(canvas). Setup has three phases:

1. Core — clear stale singletons (scene, hits_3d, animation), init renderer, camera, input events
2. Scene — this.load_scene(scenes.load()) — Scenes reads localStorage (or falls back to the bundled default), migrates, restores constants, returns a Portable_Scene. Engine tears down any existing scene and rebuilds from the portable data.
3. Input + render — wire the handlers for drag/rotate/scroll, start the animation loop

setup runs once. After that, scene switches happen through load_scene directly (library click, new-scene button, file import) — no page reload needed.

Engine construction

Runs at module init (before setup). Wires two reactive hooks:

• Edge color sync — keeps all O_Scene.color values in sync with the user's color preference
• post_propagate_hook — after any propagate or propagate_all, iterates all SOs and calls sync_repeater on any SO with a repeater config. This is how repeater clone counts stay current after dimension changes.

Scene construction

Scene construction happens at launch (phase 2 of setup calls load_scene) and again whenever the user switches scenes — clicking a library entry, importing a file, or hitting new-scene. All three go through load_scene, which tears down the current scene and rebuilds from a Portable_Scene. Two other entry points add SOs to an existing scene without replacing it: insert_child_from_text (option-click in the library) and duplicate_selected.

All five paths share the same trap, and the same rule prevents it.

The two phases

Creating SOs in bulk (load, insert, duplicate) always has two phases:

1. Build — deserialize, wire into scene tree, rebind_formulas on each SO
2. Cascade — call propagate_all() once

Never interleave them. rebind_formulas evaluates formulas immediately (sets attr.value), and propagate cascades through the entire scene — including SOs that haven't been bound yet. If you propagate clone[0] before clone[1] is bound, propagate sees clone[1] in the scene tree with value = 0 and enforces invariants on garbage. Worse, each propagate fires post_propagate_hook (sync_repeater), which adds/removes SOs mid-loop.

The pattern

// Phase 1: build
for (const so of new_sos) {
    const parent_id = so.scene?.parent?.so.id;
    if (parent_id) constraints.rebind_formulas(so, parent_id);
}

// Phase 2: cascade
constraints.propagate_all();

Three call sites follow this pattern: load_scene, insert_child_from_text, duplicate_selected. All three had bugs before adopting it.

Single-SO edits are different

propagate(so) is fine when one SO changed (drag, dimension edit, formula commit, rotation). The scene is fully bound — propagate just cascades from the changed SO outward. The rule only applies to bulk creation where new SOs coexist in a half-bound state.