fix: smooth advanced focus entrance

apps/nextjs/src/components/board/advanced-focus/advanced-focus.module.css

@@ -16,9 +16,15 @@
   box-shadow: var(--mantine-shadow-md);
   overscroll-behavior: contain;
   animation: focus-surface-in 180ms cubic-bezier(0.16, 1, 0.3, 1);
+  animation-fill-mode: backwards;
+  animation-play-state: paused;
   transform-origin: top left;
 }
 
+.surfaceReady {
+  animation-play-state: running;
+}
+
 .manualSurface {
   position: fixed;
   max-width: none;

apps/nextjs/src/components/board/advanced-focus/entrance.spec.ts

@@ -0,0 +1,62 @@
+// @vitest-environment jsdom
+
+import { afterEach, describe, expect, test, vi } from "vitest";
+
+import { startAdvancedFocusEntrance } from "./entrance";
+
+describe("startAdvancedFocusEntrance", () => {
+  afterEach(() => {
+    document.body.replaceChildren();
+    vi.unstubAllGlobals();
+  });
+
+  test("moves the persistent portal before releasing its source-frame animation", () => {
+    let releaseFrame: FrameRequestCallback | undefined;
+    vi.stubGlobal(
+      "requestAnimationFrame",
+      vi.fn((callback: FrameRequestCallback) => {
+        releaseFrame = callback;
+        return 7;
+      }),
+    );
+
+    const compactHost = document.createElement("div");
+    const previewHost = document.createElement("div");
+    const portalTarget = document.createElement("div");
+    const surface = document.createElement("div");
+    surface.classList.add("surface-ready");
+    portalTarget.append(surface);
+    compactHost.append(portalTarget);
+    document.body.append(compactHost, previewHost);
+
+    expect(startAdvancedFocusEntrance(portalTarget, previewHost, surface, "surface-ready")).toBe(7);
+    expect(portalTarget.parentElement).toBe(previewHost);
+    expect(surface.classList.contains("surface-ready")).toBe(false);
+
+    releaseFrame?.(0);
+    expect(surface.classList.contains("surface-ready")).toBe(true);
+  });
+
+  test("does not release a detached surface", () => {
+    let releaseFrame: FrameRequestCallback | undefined;
+    vi.stubGlobal(
+      "requestAnimationFrame",
+      vi.fn((callback: FrameRequestCallback) => {
+        releaseFrame = callback;
+        return 8;
+      }),
+    );
+
+    const previewHost = document.createElement("div");
+    const portalTarget = document.createElement("div");
+    const surface = document.createElement("div");
+    portalTarget.append(surface);
+    document.body.append(previewHost);
+
+    startAdvancedFocusEntrance(portalTarget, previewHost, surface, "surface-ready");
+    portalTarget.remove();
+    releaseFrame?.(0);
+
+    expect(surface.classList.contains("surface-ready")).toBe(false);
+  });
+});

apps/nextjs/src/components/board/advanced-focus/entrance.ts

@@ -0,0 +1,13 @@
+export const startAdvancedFocusEntrance = (
+  portalTarget: HTMLElement,
+  host: HTMLElement,
+  surface: HTMLElement,
+  readyClass: string,
+) => {
+  host.append(portalTarget);
+  surface.classList.remove(readyClass);
+
+  return requestAnimationFrame(() => {
+    if (surface.isConnected) surface.classList.add(readyClass);
+  });
+};