Invisible Root

turn root into a pure container — invisible by default, non-interactive in 3D, selectable via panel or background click.

decisions

• no auto-sizing. tried it, hated it. root keeps its user-set dimensions.
• manual "fit" button in the actions row. shrink_to_fit: snapshot children's absolute bounds, resize parent to their bounding box, normalize children so offsets stay non-negative.
• fit-normalize on startup if any SO has negative start/end/length (unless root is a repeater).
• root is selectable via the parts hierarchy and via background click. attributes table shows, angles table hidden.
• root visibility persists. serialize always writes visible. Engine only forces visible = false for brand new scenes.
• background click selects root. second background click deselects.

implemented

phase 1: root invisible (rendering)

• Engine.ts — if (!saved) root_so.visible = false (new scenes only)
• Engine.ts — startup fit-normalize when negatives detected (skip if root is repeater)
• R_Dimensions.ts — skip root: if (!obj.parent) continue
• Smart_Object.ts — serialize always writes visible (not just when false)

phase 2: root non-interactive in 3D (hit testing)

• Hits_3D.ts — face hit loop skips root: if (!so.scene.parent) continue
• Events_3D.ts — background click selects root (or deselects if root already selected)

phase 3: back face guidance

• Hits_3D.ts — back_most_face(so): front_most_face(so) ^ 1
• Drag.ts — when parent is root, use back_most_face instead of front_most_face

phase 4: fit button

• Engine.ts — shrink_to_fit(): snapshot children's absolute bounds, compute bounding box, resize parent, normalize children offsets. disabled for repeaters.
• D_Selected_Part.svelte — "fit" button in actions row, disabled when no children or is repeater.

phase 5: details panel

• D_Attributes.svelte — angles table wrapped in {#if !is_root} (hidden for root)
• D_Selected_Part.svelte — deselected root shows empty panel; disabled buttons use {#if} not disabled; needs_fit derived state for fit button visibility

phase 6: root_so source of truth

• Scenes.ts — root_so: Smart_Object | null = null (plain property, SOT)
• Stores.ts — removed w_root_so writable store and root_so getter entirely
• Engine.ts, Render.ts, R_Grid.ts, Events_3D.ts, Graph.svelte — all read scenes.root_so

phase 7: HMR fix

• Events.ts — private wired = false guard prevents double document listener registration on HMR re-mount

contextual selectability

when a saved file is inserted, its root becomes a child. insert_child_from_text sets parent, so !so.scene.parent checks already treat it as non-root. SO stays invisible in both contexts. no code changes needed.