Prevent stale live snapshots from flickering sorted packages

tests/visual/sort-regression.tsx

@@ -0,0 +1,85 @@
+import { createRoot } from "react-dom/client";
+import { App } from "../../src/renderer/App";
+import type { ElectronApi } from "../../src/shared/preload-api";
+import { sortPackageOrderByAvailability } from "../../src/renderer/package-order";
+import { createVisualFixture } from "./fixtures";
+import { createVisualElectronApi } from "./mock-electron-api";
+import "../../src/renderer/theme.css";
+import "../../src/renderer/styles.css";
+
+const fixture = createVisualFixture("dense");
+fixture.snapshot.settings.animatePackageDisclosure = true;
+const listeners = new Set<Parameters<ElectronApi["onStateUpdate"]>[0]>();
+const emit = (): void => {
+  fixture.snapshot.snapshotRevision = (fixture.snapshot.snapshotRevision ?? 0) + 1;
+  for (const listener of listeners) listener(structuredClone(fixture.snapshot));
+};
+window.rd = {
+  ...createVisualElectronApi(fixture),
+  onStateUpdate: (listener) => {
+    listeners.add(listener);
+    return () => listeners.delete(listener);
+  },
+  reorderPackages: async (order) => {
+    emit();
+    await new Promise((resolve) => setTimeout(resolve, 750));
+    fixture.snapshot.session.packageOrder = [...order];
+    emit();
+  }
+};
+
+const report = document.createElement("output");
+report.style.cssText = "position:fixed;bottom:0;left:0;z-index:9999;background:#fff;color:#111;font-size:12px;padding:8px";
+report.textContent = "Prüfung wird vorbereitet";
+document.body.append(report);
+createRoot(document.getElementById("root")!).render(<App />);
+
+async function verify(): Promise<void> {
+  const frame = (): Promise<void> => new Promise((resolve) => requestAnimationFrame(() => resolve()));
+  const findSortButton = (): HTMLButtonElement | undefined => [...document.querySelectorAll<HTMLButtonElement>("button")]
+    .find((button) => /^Verfügbarkeit(?: [↑↓])?$/.test(button.textContent?.trim() ?? ""));
+  for (let attempt = 0; attempt < 180 && !findSortButton(); attempt++) await frame();
+  const sortButton = findSortButton();
+  if (!sortButton) throw new Error("Verfügbarkeitsspalte fehlt");
+  const results = [];
+  for (let turn = 0; turn < 4; turn++) {
+    const expected = sortPackageOrderByAvailability(
+      fixture.snapshot.session.packageOrder,
+      fixture.snapshot.session.packages,
+      fixture.snapshot.session.items,
+      turn % 2 === 1
+    ).map((id) => fixture.snapshot.session.packages[id].name);
+    let wrongOrderUpdates = 0;
+    const orderChanges: string[][] = [];
+    const body = document.querySelector<HTMLElement>(".downloads-table-body")!;
+    const observer = new MutationObserver(() => {
+      const actual = [...body.querySelectorAll("article strong")].map((element) => element.textContent ?? "");
+      if (JSON.stringify(actual) !== JSON.stringify(orderChanges.at(-1))) orderChanges.push(actual);
+      if (JSON.stringify(actual) !== JSON.stringify(expected)) wrongOrderUpdates++;
+    });
+    observer.observe(body, { childList: true, subtree: true });
+    sortButton.click();
+    const deadline = performance.now() + 1600;
+    let frames = 0;
+    let wrongOrderFrames = 0;
+    let movingFrames = 0;
+    while (performance.now() < deadline) {
+      await frame();
+      frames++;
+      const body = document.querySelector<HTMLElement>(".downloads-table-body")!;
+      const actual = [...body.querySelectorAll("article strong")].map((element) => element.textContent);
+      if (JSON.stringify(actual) !== JSON.stringify(expected)) wrongOrderFrames++;
+      const rows = [...body.querySelectorAll<HTMLElement>(".downloads-virtual-row")];
+      if (rows.some((row) => {
+        const target = Number.parseFloat(row.style.getPropertyValue("--downloads-virtual-row-top"));
+        const transform = new DOMMatrixReadOnly(getComputedStyle(row).transform);
+        return Math.abs(transform.m42 - target) > 0.5;
+      })) movingFrames++;
+    }
+    observer.disconnect();
+    results.push({ direction: turn % 2 === 1 ? "offline-first" : "online-first", frames, wrongOrderFrames, wrongOrderUpdates, movingFrames, orderChanges });
+  }
+  report.textContent = JSON.stringify({ passed: results.every((result) => result.wrongOrderFrames === 0 && result.wrongOrderUpdates === 0 && result.movingFrames === 0), results });
+}
+
+void verify().catch((error) => { report.textContent = String(error); });