feat: 实现 Chromium PDF 导出与精确预览

apps/web/tests/pdf-page-geometry.test.ts

@@ -0,0 +1,25 @@
+import { describe, expect, it } from "vitest";
+import {
+  getPdfCanvasRenderScale,
+  getPdfPageCssDimensions,
+  PDF_PAGE_CSS_SCALE
+} from "../src/pdf-page-geometry";
+
+describe("精确 PDF 页面尺寸", () => {
+  it("按 96 CSS PPI 映射 PDF 点尺寸", () => {
+    expect(PDF_PAGE_CSS_SCALE).toBeCloseTo(4 / 3);
+    expect(
+      getPdfPageCssDimensions(595.275591, 841.889764)
+    ).toEqual({
+      width: expect.closeTo(793.700788, 5),
+      height: expect.closeTo(1122.519685, 5)
+    });
+  });
+
+  it("结合显示宽度和设备像素比计算 Canvas 比例", () => {
+    expect(getPdfCanvasRenderScale(600, 800, 2)).toBeCloseTo(
+      8 / 3
+    );
+    expect(getPdfCanvasRenderScale(0, 800, 2)).toBe(0);
+  });
+});