feat(studio): arrow-key nudge step math (unwired)

[ukimsanov]

What

domEditNudge — pure nudge-step math (direction × modifier → delta, commit debounce constant) with tests. Shipped unwired.

Why

small standalone concept consumed by the canvas nudge hook in the chrome-components PR.

How

new files; one TEMP(studio-dnd) ignoreExports entry until the consumer lands (removed by the app-shell swap PR).

Test plan

bunx vitest run domEditNudge.test.ts; tsc --noEmit; fallow audit clean.

---

Stack position 12/25 — studio NLE overhaul (CapCut-parity timeline + canvas). Graphite manages bases; merge from #2192 upward. Temporary TEMP(studio-dnd) fallow entries (unwired-component windows) are all removed by #2213 (app-shell swap), whose tree is byte-identical to the fully-verified integration branch.

[ukimsanov]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• feat(studio): assets/blocks panel behaviors + preview helpers #2216
• feat(studio): timeline visual refresh #2215
• feat(studio): clip thumbnail modules #2214
• feat(studio): app shell swap — mount EditorShell, retire the legacy engine #2213
• feat(studio): timeline glue swap — Timeline/TimelineCanvas onto the NLE engine #2212
• feat(studio): canvas glue swap — overlay, gestures, selection to final form #2211
• feat(studio): sidebar asset card (unwired) #2210
• feat(studio): NLE shell assembly (unwired) #2209
• feat(studio): canvas chrome components (unwired) #2208
• feat(studio): timeline interaction hooks and lanes component (unwired) #2207
• feat(studio): clip drag engine — preview and commit (unwired) #2206
• feat(studio): glue API coexistence layer for the NLE swap #2205
• feat(studio): NLE shell components — context provider, panes, overlays (unwired) #2204
• feat(studio): arrow-key nudge step math (unwired) #2203 👈 (View in Graphite)
• feat(studio): canvas context menu and z-order actions (unwired) #2202
• test(studio): characterization suites for resize commit and razor history #2201
• feat(studio): asset click policy and canvas nudge gate #2200
• feat(studio): timeline lane-zone model #2199
• feat(studio): timeline z-stacking sync model #2198
• feat(studio): multi-clip drag preview math #2197
• feat(studio): timeline magnetic snapping #2196
• feat(studio): timeline collision and placement model #2195
• feat(studio-server): files route extensions #2194
• feat(studio): seek-restore contract for player reloads #2193
• feat(studio): timeline leaf helpers — audio inspector, zoom math, UI prefs #2192
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[miga-heygen]

Reviewed as part of the 25-PR NLE overhaul stack. Full stack review on #2205 (the keystone). No blockers on this PR. — Miga

[vanceingalls]

Verdict: LGTM (green) — smallest of the batch, correct at every boundary

Two pure helpers: resolveCanvasNudgeDelta maps arrow keys (plain / Shift) to a { dx, dy } in composition pixels; canCanvasNudgeTargets gates the whole nudge on target capabilities. Nothing to trip over.

The pointed queries

• Step math is unambiguous. packages/studio/src/components/editor/domEditNudge.ts:11–:12 — CANVAS_NUDGE_STEP_PX = 1, CANVAS_NUDGE_SHIFT_STEP_PX = 10. Constants are integers in composition-space pixels; the returned { dx, dy } is likewise in pixels. Test at :24–:52 pins all four cardinal directions × {plain, Shift}.
• Chord passthrough. :28 rejects metaKey || ctrlKey || altKey → returns null so browser/app shortcuts route past the nudge. Tested at :54–:58 for all three modifiers. Correct.
• Non-arrow rejection. :29 gates on CANVAS_NUDGE_KEYS.has(event.key); non-arrows fall through to null. Tested at :60–:63.
• Target-capability gate. canCanvasNudgeTargets at :42–:44 requires at least one target AND every target's canApplyManualOffset === true. Test at :66–:79 covers [] (false), [movable] (true), [movable, movable] (true), [locked] (false), [movable, locked] (false). All four boundary cases.
• Debounce constant. :14 (CANVAS_NUDGE_COMMIT_DEBOUNCE_MS = 400) is exported but not yet consumed at this SHA — exempted in .fallowrc.jsonc at :93–:97 with the TEMP marker pointing at studio-dnd/pr22. Honest.
• No accumulation logic here. Delta accumulation for holding an arrow key (the "burst commit" pattern named in the docstring at :13) is NOT in this file — it belongs to the wiring PR. This module is a pure per-event mapper. Right scope.
• Wiring with #2200 (canvas nudge gate). No import at this SHA — verified via grep against DomEditOverlay.tsx head. As with #2200, the pair is expected to be wired together by studio-dnd/pr22. This PR's math is independently testable and it is tested.

R1 by Via

[miguel-heygen]

Re-review at current head d103af6: diff remains unwired pure step math, prior tests and contracts intact; required checks green. Approving.

[miguel-heygen]

Re-reviewed current head and verified the addressed feedback and required behavior. Approval is for this exact head; Graphite mergeability may still be pending.