Edit Mode

The editor has one edit-mode slot: at most one nested editing context is active, it owns the canvas's meaning while it lives — chrome, tools, and keys re-resolve against it (routing capture layer) — and Enter is the front door while Escape is the way out. The production editor models this slot as a flat union of six "content edit modes." This document specifies the slot's mechanics, and — because two of the six members are legacy or mislabeled — replaces the flat union with a taxonomy that says honestly what each mode edits.

The slot

• Exclusive: at most one mode at a time. Entering a mode ends the previous one through its normal exit (cleanup runs; nothing is abandoned).
• Domain: the active mode is authoring context (golden state model) — undoable, never persisted to file, replicated at most as presence. Undo that crosses the mode's entry ends the mode.
• Subject-pinned: a mode addresses one subject — a node, or one paint of a node — fixed at entry. If the subject is deleted (or undone away), the mode ends without residue.
• Capture: while a mode is active it sits above the binding table in the routing ladder; keys mean what the mode says first.

The taxonomy

Classify by the subject of editing, not by how the mode happens to be entered:

Content modes — the node's material

Text and vector edit the node's content — the very thing the node is. They are what the name "content edit" honestly describes:

• Entered by the enter idiom — Enter on a single selected node or the double-click descent (traversal TRAV-1, targeting TGT-4).
• Exited by the Escape ladder; content modes may have internal rungs (vector's disconnect → tool → exit; text exits in one). Pointing outside the subject also exits — the enter idiom's inverse (vector: double-click on empty canvas, VEC-13; text: the session's outside-click commit).
• Carry the cleanup doctrine: empty authoring leaves no trace — an empty text node is deleted at exit, a degenerate vector network is deleted at exit, and an untouched subject is restored exactly (vector-edit VEC-1/2; the text twin is contract-bound below).
• May host their own tools (vector: pen, bend, lasso, width) and their own nested undo (text's session undo drains before document undo).

Facets — a lens inside a content mode

The production union carries a width mode as a peer of text and vector. It is not a peer. Every fact about it says nested: it can only be entered from vector editing (its tool is illegal anywhere else), it operates on the same node and carries the vector context across, and — uniquely in the union — exiting it returns to vector mode rather than to selection. The flat union cannot express nesting, so production fakes it with a tool-revert side channel.

This spec models it structurally: the vector content mode has a facet — geometry (the default: vertices, segments, tangents) or width (the variable-width profile: stops at parametric positions along the curve, each with a radius). The width tool switches the facet; leaving the facet lands on geometry of the same mode, same node. A facet is not a second slot entry: Escape from the width facet steps to the geometry facet, then the ordinary vector ladder continues. Future lenses over the same material (e.g. a paint-points facet) join as facets, not as new union members.

Paint sessions — a property's value

Gradient and image editing operate on a paint — one entry of a fill/stroke paint list — not on the node's content. Calling them "content edit modes" is the squat this review removes. They are paint sessions:

• Subject: (node, fill|stroke, paint index) — a property address.
• Entered from the paint's own control: expanding a gradient or image paint in the properties panel opens the session; the panel control and the canvas chrome are two views of one state. One canvas entry exists by user-intent dispatch: double-clicking a shape whose fill is an image means "edit the image" and opens the image session (see the dispatch table). Enter never opens a paint session.
• Exited by Escape (one press — sessions have no internal rungs), by collapsing the panel control, or structurally: re-typing the paint away (gradient → solid) or removing it ends the session.
• No cleanup doctrine: edits commit against the paint as they happen; there is no "empty paint" to delete.
• Session chrome: gradient — the transform control points and the color-stop track (drag stops, double-click to insert, arrows step the selected stop, delete removes it); image — the transformed image quad with side handles (scale), corner handles (rotate), and body drag (translate).

Excluded: the production union's bitmap member is legacy and is not part of this spec; raster editing, if it returns, would be a content mode (it edits a node's material) and must re-enter through this taxonomy.

The dispatch table

The enter idiom resolves by the subject, in this order:

Selected subject	Result
text node	text content mode
shape/vector with an image fill	image paint session (user intent: "edit the image")
vector node	vector content mode
path-reducible primitive (rectangle, ellipse, polygon, star, line)	flatten, then vector content mode (entry is a commitment — vector-edit)
container / anything else	not enterable — Enter falls through to select-children (TRAV-1)

Gradient sessions have no row: they are reachable only from the paint control, because a gradient has no canvas-hit identity apart from the node that carries it.

Tools and modes

Each mode declares its legal tool set; the slot and the tool system compose, never race:

Mode	Legal tools
text	(none — the session owns input)
vector / geometry facet	cursor, pen, bend, lasso
vector / width facet	width (the facet is the tool)
paint sessions	cursor only

Arming a tool outside its mode's legal set is refused (tool reserved-key discipline); arming a mode-scoped tool (lasso, bend, width) outside its mode is a no-op. Exiting a mode reverts mode-scoped tools to cursor.

Escape, end to end

One press, one rung, across the whole system (routing ROUTE-5):

width facet      → geometry facet
vector: sub-selection or pen projection → clear (disconnect)
vector: non-cursor tool → cursor
any active mode  → exit the mode
non-cursor tool  → cursor
selection        → deselect

Contracts

• MODE-1 Exclusivity: entering any mode while another is active runs the previous mode's full exit (cleanup included) before the new mode exists; no observable state ever holds two modes.
• MODE-2 Dispatch: the enter idiom resolves exactly per the dispatch table; Enter never opens a paint session; a gradient session is unreachable from the canvas alone.
• MODE-3 Text cleanup twin: exiting text mode with empty content deletes the node; exiting with unchanged content leaves document and history untouched (binds VEC-1/2's doctrine to text).
• MODE-4 Facet nesting: the width facet is enterable only from vector mode, addresses the same node, and Escape from it lands on the geometry facet of the same mode — never on plain selection.
• MODE-5 Panel–session agreement: a paint session is active iff its paint control is open; expanding enters, collapsing exits, and re-typing or removing the paint ends the session in the same dispatch.
• MODE-6 Subject pinning: deleting the subject node, or undoing past the mode's entry, ends the mode with no residue (no orphan chrome, no dangling session state).
• MODE-7 Domain: the active mode round-trips through undo/redo as authoring context and never appears in a saved document.
• MODE-8 Tool legality: no input sequence arms a tool outside the active mode's legal set; mode-scoped tools are no-ops outside their mode.
• MODE-9 Session undo drains first: inside text mode, undo consumes the session's own steps before touching document history; the committed result is one document entry.
• MODE-10 Escape is total and single-stepped: from any state in this document, repeated Escape reaches plain no-selection in finitely many presses, one rung per press, through the ladder above.