feat: 实现 Chromium PDF 导出与精确预览

apps/web/tests/pdf-render-queue.test.ts

@@ -0,0 +1,85 @@
+import { describe, expect, it, vi } from "vitest";
+import { PdfPageRenderQueue } from "../src/pdf-render-queue";
+
+async function flushPromises() {
+  await new Promise((resolve) => setTimeout(resolve, 0));
+}
+
+describe("PdfPageRenderQueue", () => {
+  it("限制并发并优先渲染可见页", async () => {
+    const queue = new PdfPageRenderQueue(1);
+    const order: number[] = [];
+    let releaseFirst: (() => void) | undefined;
+
+    queue.schedule(
+      1,
+      () =>
+        new Promise<void>((resolve) => {
+          order.push(1);
+          releaseFirst = resolve;
+        })
+    );
+    queue.schedule(2, async () => {
+      order.push(2);
+    });
+    queue.schedule(8, async () => {
+      order.push(8);
+    });
+    queue.setVisible(8, true);
+
+    expect(order).toEqual([1]);
+    releaseFirst?.();
+    await flushPromises();
+    expect(order).toEqual([1, 8, 2]);
+  });
+
+  it("优先预渲染滚动方向上的相邻页面", async () => {
+    const queue = new PdfPageRenderQueue(1);
+    const order: number[] = [];
+    let releaseFirst: (() => void) | undefined;
+
+    queue.schedule(
+      5,
+      () =>
+        new Promise<void>((resolve) => {
+          order.push(5);
+          releaseFirst = resolve;
+        })
+    );
+    queue.setVisible(5, true);
+    queue.setVisible(5, false);
+    queue.setVisible(6, true);
+    queue.schedule(4, async () => {
+      order.push(4);
+    });
+    queue.schedule(7, async () => {
+      order.push(7);
+    });
+
+    releaseFirst?.();
+    await flushPromises();
+    expect(order).toEqual([5, 7, 4]);
+  });
+
+  it("取消尚未开始的任务", async () => {
+    const queue = new PdfPageRenderQueue(1);
+    let releaseFirst: (() => void) | undefined;
+    const cancelledTask = vi.fn();
+
+    queue.schedule(
+      1,
+      () =>
+        new Promise<void>((resolve) => {
+          releaseFirst = resolve;
+        })
+    );
+    const cancel = queue.schedule(2, async () => {
+      cancelledTask();
+    });
+    cancel();
+
+    releaseFirst?.();
+    await flushPromises();
+    expect(cancelledTask).not.toHaveBeenCalled();
+  });
+});