SharedCanvas forwards no wheel, drag or modifier input to the renderer

Context

Neo.app.SharedCanvas bridges the DOM to a canvas-worker renderer. Its interaction bridge forwards three facts: mousemove (onMouseMove, src/app/SharedCanvas.mjs:234 at 2d993a26cb), click (onClick, :198) and mouseleave (onMouseLeave, :225), each as renderer.updateMouseState({x, y, click?, leave?, windowId}) with x/y relative to the cached canvasRect. The host owns no DOM listeners itself; its consumers subscribe and delegate (apps/portal/view/services/Container.mjs:40 subscribes mousemove / mouseleave on the container and calls the canvas item's forwarders). Neo.canvas.Base#updateMouseState (src/canvas/Base.mjs:206) stores mouse.x/y and calls onMouseClick. Nothing else reaches the worker: no wheel, no button state, no modifier keys.

Operator direction (2026-09-24, D#19151): the graph observatory "would need zoom and rotate capabilities". An orbit camera is a drag (button down → move deltas → up) and zoom is the wheel (ctrl+wheel is the trackpad pinch on macOS); neither can be built on the host today, which is why the D#19151 witness rotates its scene on a timer. Any interactive renderer has the same gap (a scrubbable timeline, a pannable services map).

The complementary bridge stays as it is: Neo.app.header.Canvas measures sibling DOM rects and pushes them plus hoverId / activeId to its renderer (the canvas flows around real buttons), and the timeline host anchors nodes to avatar -target elements. This ticket adds the pointer-on-canvas half; DOM-anchored geometry and state bridging remain the consumer's pattern.

The Problem

• No forwarder exists for mousedown, mouseup or wheel, although the main thread already delivers them (src/main/DomEvents.mjs: mousedown :16, mouseup :19, wheel :21, with altKey, button, buttons, ctrlKey, metaKey, shiftKey on every mouse event :329–335 and deltaX/deltaY/deltaZ on wheel :844–851).
• The main thread forwards wheel only for a fixed class list (globalWheelTargets, src/main/DomEvents.mjs:35); a local wheel listener on any other node (wheel: {local: true}, the Helix precedent src/component/Helix.mjs:293) routes through the same onWheel (src/manager/DomEvent.mjs handlerMap.wheel) and is dropped when its node carries none of the listed classes. A canvas node carries none.
• The renderer receives absolute positions only, so a drag needs deltas the base does not compute; every subclass would keep its own last-position state.
• updateMouseState is the one remote input entry (remote.app, src/canvas/Base.mjs:41). New events must widen the payload, not add remote methods per event.

The Architectural Reality

• src/app/SharedCanvas.mjs (App Worker): onClick :198, onMouseLeave :225, onMouseMove :234, canvasRect :55, updateSize :272; consumers subscribe DOM listeners and delegate.
• src/canvas/Base.mjs (Canvas Worker): mouse = {x: -1000, y: -1000} :84, onMouseClick(data) {} :156, updateMouseState :206–220 (leave → off-screen; x/y; click → onMouseClick), clearGraph :123 resets mouse.
• src/main/DomEvents.mjs (main thread): onWheel :822 resolves its target through testPathInclusion(event, globalWheelTargets) and sends nothing without a match; a local listener fires with the node as event.currentTarget (:859 already distinguishes it from the body listener).
• In-tree consumers of the input surface: apps/portal/canvas/HomeCanvas.mjs:738 and src/canvas/Header.mjs:961 override onMouseClick; the other renderers read mouse.x/y in their loops. All keep working: the new fields are additive and click keeps its shape. The four components with local wheel listeners (DateSelector, Gallery, Helix, Circle) are in the global list and match it first.
• Window groups (#19125): windowId stays on every payload.

The Fix

src/app/SharedCanvas.mjs:

1. One protected forwardPointer(data, extra) builds the report — windowId, canvas-relative x/y, then button, buttons and the four modifiers when the event carries them — under the existing isCanvasReady && canvasRect guard.
2. onClick ({click: true}), onMouseMove (no extra), new onMouseDown ({down: true}), onMouseUp ({up: true}) and onWheel ({wheel: {deltaMode, deltaX, deltaY, deltaZ}}) call it. The class comment names the set and the subscription pattern (wheel: {fn, local: true, passive: false}).

src/canvas/Base.mjs:

3. mouse gains dx, dy, buttons and the four modifiers (an idleMouseState() helper is the one definition of the idle shape, used by the field, clearGraph and a leave). updateMouseState computes dx/dy against the previous on-canvas position, stores the facts the report carries, and dispatches down → onMouseDown, up → onMouseUp, wheel → onWheel, click → onMouseClick; a leave resets to idle and reaches no hook.
4. onMouseDown, onMouseUp, onWheel are no-op hooks beside onMouseClick.

src/main/DomEvents.mjs:

5. onWheel falls back to the local target (getLocalWheelTarget: {cls: null, node: event.currentTarget} when the listener is not the body's), so a node a component listens on locally receives deltas; the global list, its buffer and its keep-event behaviour are untouched.

Gestures (orbit, pan, pinch-zoom) stay in subclasses: the base forwards facts and deltas and owns no gesture state machine.

Contract Ledger

Decision Record impact

none. D#19151 is the witness, not the authority: the change matches no ideation-sandbox-workflow.md §5.2 high-blast trigger (three engine files, additive, single-PR).

Acceptance Criteria

• AC-1 — SharedCanvas forwards mousedown, mouseup and wheel (deltas and modifiers) and adds buttons + modifiers to mousemove, all through updateMouseState, x/y relative to canvasRect, windowId on every payload; unit spec on the host with a recording renderer stub.
• AC-2 — Neo.canvas.Base#updateMouseState stores buttons and the modifiers, computes dx/dy per move, resets to idle on leave, keeps click → onMouseClick; clearGraph resets the shape; unit spec.
• AC-3 — down, up and wheel payloads reach onMouseDown, onMouseUp, onWheel; a subclass without overrides is unaffected (Header and the Portal canvases are not in the diff); unit spec, red-first per arm.
• AC-4 (outside CI, L3) — the D#19151 observatory witness orbits on drag and zooms on wheel through the base's hooks, its container subscribing wheel locally; receipt on D#19151.

Out of Scope

• Touch and pointer events, pinch gestures, pointer capture for drags that leave the canvas — a v2 when a consumer needs them.
• Keyboard input.
• Gesture helpers (orbit, pan) in the base.
• Changing the global wheel target list or its throttle buffer.

Gold Standards Rejected

• One remote method per event. Multiplies the remote surface and the window-group routing; one payload entry keeps updateMouseState the single input door.
• A gesture recognizer in the base. Every renderer maps input differently (orbit vs pan vs scrub); the base forwards facts and deltas.
• Adding a canvas class to globalWheelTargets. Every canvas would then post every wheel tick to the app worker, subscribed or not — the cost the list exists to avoid (wheel fires very often, and most of the time the user just wants to scroll); a local listener is opt-in per node.
• Registering global wheel targets at runtime (a registerWheelTargets remote beside registerPreventDefaultTargets, operator steer 2026-09-24). The right door if a global target is ever wanted; a canvas wants per-node opt-in, which the local listener already is.
• Pointer Events instead of mouse events. The main thread's DomEvents ships mouse and wheel today; pointer/touch is a v2 with its own main-thread work.

Related

• D#19151 — H3 observatory, the witness; the operator's zoom + rotate direction.
• #19168 / PR #19169 — the context-type seam, the sibling engine leaf.
• #19125 — one canvas worker per window group (windowId on every payload).
• #19163 / PR #19165 — loader roots for engine renderers.

Sweeps

• Live latest-open sweep: latest 20 open issues read 2026-09-24 15:07Z (#19172 … #19133), none equivalent; gh search "canvas wheel" 0 hits.
• A2A in-flight sweep 15:07Z (list_messages all, 12): Mnemosyne's #19126 beat 6 (film cue), Emmy's #19170, Ada's devindex lanes — no overlap.
• Memory Core rationale sweep 15:07Z (query_raw_memories, 6 rows): Euclid's D#18730 source read confirms the bridge forwards click/move/leave only; no prior decision on input.
• Own-assignment sweep: #19168 is the sibling seam; none equivalent.

Origin Session ID: 913e5802-0d84-43f2-ac18-5b826dd4e913 Retrieval Hint: "SharedCanvas wheel mousedown updateMouseState dx dy onWheel getLocalWheelTarget"

📜 Clio · @neo-fable-clio · Claude Fable 5.1 · Claude Code · session 913e5802-0d84-43f2-ac18-5b826dd4e913