feat(studio): automation selection slice

packages/studio/src/player/store/automationSelectionSlice.test.ts

@@ -0,0 +1,14 @@
+import { describe, expect, it } from "vitest";
+import { usePlayerStore } from "./playerStore";
+
+describe("automationSelectionSlice", () => {
+  it("stores one ordered selection and clears it", () => {
+    const store = usePlayerStore.getState();
+    store.setAutomationSelection({ elementKey: "bgm", target: "volume", t0: 2, t1: 1 });
+    const sel = usePlayerStore.getState().automationSelection;
+    // Ordered on write, so every consumer can assume t0 < t1.
+    expect(sel).toEqual({ elementKey: "bgm", target: "volume", t0: 1, t1: 2 });
+    usePlayerStore.getState().clearAutomationSelection();
+    expect(usePlayerStore.getState().automationSelection).toBeNull();
+  });
+});

packages/studio/src/player/store/automationSelectionSlice.ts

@@ -0,0 +1,38 @@
+/**
+ * The active time selection on one automation lane.
+ *
+ * A store slice, not lane-local state, for the same reason keyframe selection
+ * is one: Delete/copy/paste handlers and the shape menu live outside the lane
+ * component and need to read it. Ephemeral by construction — nothing
+ * serializes store state, and the selection must never survive into a render.
+ */
+import type { StoreApi } from "zustand";
+
+export interface AutomationSelection {
+  /** TimelineElement key (key ?? id) of the clip that owns the lane. */
+  elementKey: string;
+  /** Lane target: "volume" or "fx.<nodeId>.<param>". */
+  target: string;
+  /** Clip-local seconds; always t0 < t1 (ordered on write). */
+  t0: number;
+  t1: number;
+}
+
+export interface AutomationSelectionSlice {
+  automationSelection: AutomationSelection | null;
+  setAutomationSelection: (sel: AutomationSelection) => void;
+  clearAutomationSelection: () => void;
+}
+
+export function createAutomationSelectionSlice(
+  set: StoreApi<AutomationSelectionSlice>["setState"],
+): AutomationSelectionSlice {
+  return {
+    automationSelection: null,
+    setAutomationSelection: (sel) =>
+      set({
+        automationSelection: sel.t0 <= sel.t1 ? sel : { ...sel, t0: sel.t1, t1: sel.t0 },
+      }),
+    clearAutomationSelection: () => set({ automationSelection: null }),
+  };
+}

packages/studio/src/player/store/playerStore.ts

@@ -10,6 +10,10 @@ import {
 } from "../../utils/studioUiPreferences";
 import { clampTimelineZoomPercent, computePinnedZoomPercent } from "../components/timelineZoom";
 import { createKeyframeSlice, type KeyframeCacheEntry, type KeyframeSlice } from "./keyframeSlice";
+import {
+  createAutomationSelectionSlice,
+  type AutomationSelectionSlice,
+} from "./automationSelectionSlice";
 
 export type { KeyframeCacheEntry } from "./keyframeSlice";
 
@@ -40,7 +44,7 @@ function resolveElementSelection(
   };
 }
 
-interface PlayerState extends KeyframeSlice {
+interface PlayerState extends KeyframeSlice, AutomationSelectionSlice {
   isPlaying: boolean;
   currentTime: number;
   duration: number;
@@ -296,6 +300,8 @@ export const usePlayerStore = create<PlayerState>((set, get) => ({
     timelineSessionEpoch: get().timelineSessionEpoch,
   })),
 
+  ...createAutomationSelectionSlice(set),
+
   activeKeyframePct: null,
   setActiveKeyframePct: (pct) => set({ activeKeyframePct: pct }),
   motionPathArmed: false,