feat(studio): support preview panning with mouse and trackpad (#888)

* feat(studio): support middle-mouse panning in preview

* feat(studio): support trackpad panning in preview

* chore(core): remove stray compositionRoot helper

Author: func25

packages/studio/src/components/nle/NLELayout.tsx

@@ -310,7 +310,7 @@ export const NLELayout = memo(function NLELayout({
     >
       {/* Preview + player controls */}
       <div className="flex-1 min-h-0 flex flex-col">
-        <div className="flex-1 min-h-0 relative">
+        <div className="flex-1 min-h-0 relative" data-preview-pan-surface="true">
           <NLEPreview
             projectId={projectId}
             iframeRef={iframeRef}

packages/studio/src/components/nle/NLEPreview.test.ts

@@ -1,5 +1,101 @@
-import { describe, expect, it } from "vitest";
-import { getPreviewPlayerKey } from "./NLEPreview";
+// @vitest-environment happy-dom
+
+import React, { act, createRef } from "react";
+import { createRoot } from "react-dom/client";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import { NLEPreview, getPreviewPlayerKey } from "./NLEPreview";
+
+globalThis.IS_REACT_ACT_ENVIRONMENT = true;
+
+vi.mock("../../player", async () => {
+  const React = await import("react");
+
+  return {
+    Player: React.forwardRef(function MockPlayer(
+      props: {
+        onLoad?: () => void;
+        style?: React.CSSProperties;
+      },
+      ref: React.ForwardedRef<HTMLIFrameElement>,
+    ) {
+      React.useEffect(() => {
+        props.onLoad?.();
+      }, [props]);
+
+      return React.createElement("div", {
+        ref: ref as React.ForwardedRef<HTMLDivElement>,
+        "data-testid": "mock-player",
+        style: props.style,
+      });
+    }),
+  };
+});
+
+vi.mock("../../utils/studioUiPreferences", () => ({
+  readStudioUiPreferences: () => ({}),
+  writeStudioUiPreferences: () => {},
+}));
+
+class MockResizeObserver {
+  observe() {}
+  disconnect() {}
+}
+
+const originalResizeObserver = globalThis.ResizeObserver;
+
+function setRect(node: Element, rect: { width: number; height: number }) {
+  Object.defineProperty(node, "getBoundingClientRect", {
+    configurable: true,
+    value: () => ({
+      x: 0,
+      y: 0,
+      left: 0,
+      top: 0,
+      right: rect.width,
+      bottom: rect.height,
+      width: rect.width,
+      height: rect.height,
+      toJSON: () => ({}),
+    }),
+  });
+}
+
+function renderPreview() {
+  const host = document.createElement("div");
+  document.body.append(host);
+  const root = createRoot(host);
+  const iframeRef = createRef<HTMLIFrameElement>();
+
+  act(() => {
+    root.render(
+      React.createElement(NLEPreview, {
+        projectId: "timeline-edit-playground",
+        iframeRef,
+        onIframeLoad: () => {},
+      }),
+    );
+  });
+
+  const viewport = host.querySelector('[aria-label="Composition preview"]') as HTMLDivElement;
+  const stage = host.querySelector('[data-testid="preview-zoom-stage"]') as HTMLDivElement;
+  expect(viewport).toBeTruthy();
+  expect(stage).toBeTruthy();
+
+  setRect(viewport, { width: 800, height: 600 });
+
+  return {
+    host,
+    root,
+    viewport,
+    stage,
+    cleanup() {
+      act(() => {
+        root.unmount();
+      });
+      host.remove();
+    },
+  };
+}
 
 describe("getPreviewPlayerKey", () => {
   it("keeps the same player identity when only refreshKey changes", () => {
@@ -30,3 +126,70 @@ describe("getPreviewPlayerKey", () => {
     );
   });
 });
+
+describe("NLEPreview", () => {
+  beforeEach(() => {
+    globalThis.ResizeObserver = MockResizeObserver as typeof ResizeObserver;
+  });
+
+  afterEach(() => {
+    globalThis.ResizeObserver = originalResizeObserver;
+  });
+
+  it("pans the preview with middle mouse drag", () => {
+    const view = renderPreview();
+    const target = document.createElement("div");
+    view.stage.appendChild(target);
+
+    act(() => {
+      target.dispatchEvent(
+        new PointerEvent("pointerdown", {
+          bubbles: true,
+          pointerId: 1,
+          button: 1,
+          clientX: 240,
+          clientY: 180,
+        }),
+      );
+      document.dispatchEvent(
+        new PointerEvent("pointermove", {
+          bubbles: true,
+          pointerId: 1,
+          clientX: 300,
+          clientY: 220,
+        }),
+      );
+      document.dispatchEvent(
+        new PointerEvent("pointerup", {
+          bubbles: true,
+          pointerId: 1,
+        }),
+      );
+    });
+
+    expect(view.stage.style.transform).toContain("translate(48px, 40px)");
+    view.cleanup();
+  });
+
+  it("pans the preview with a two-finger wheel gesture", () => {
+    const view = renderPreview();
+    const target = document.createElement("div");
+    view.stage.appendChild(target);
+
+    act(() => {
+      target.dispatchEvent(
+        new WheelEvent("wheel", {
+          bubbles: true,
+          cancelable: true,
+          clientX: 240,
+          clientY: 180,
+          deltaX: -30,
+          deltaY: 24,
+        }),
+      );
+    });
+
+    expect(view.stage.style.transform).toContain("translate(30px, -24px)");
+    view.cleanup();
+  });
+});