fix: 修复预览与 PDF 渲染边界问题

apps/web/src/paged-document-runtime.ts

@@ -2,10 +2,14 @@ import highlightCss from "highlight.js/styles/github.css?inline";
 import katexCss from "katex/dist/katex.min.css?inline";
 import { Previewer } from "pagedjs";
 import { createMermaidSiteConfig } from "./mermaid-config";
-import { fitOversizedMermaidToPage } from "./mermaid-page-fit";
+import {
+  fitOversizedMermaidToPage,
+  getPageContentDimensions
+} from "./mermaid-page-fit";
 import { renderMermaidDefinitions } from "./mermaid-renderer";
 import { replaceMermaidSvgWithImages } from "./mermaid-static-image";
 import type { MermaidOutputMode } from "./mermaid-static-image";
+import { enablePrintMediaForPreview } from "./preview-styles";
 import "./paged-table-handler";
 import {
   buildPagedMediaCss,
@@ -70,6 +74,54 @@ function stylesheet(
   };
 }
 
+function mountMeasurementContainer(
+  documentRef: Document,
+  content: DocumentFragment,
+  payload: PagedPreviewPayload,
+  target: PagedRenderTarget
+) {
+  const pageContent = getPageContentDimensions(payload.exportConfig);
+  const style = documentRef.createElement("style");
+  const themeCss =
+    target === "preview"
+      ? enablePrintMediaForPreview(payload.themeCss)
+      : payload.themeCss;
+  style.dataset.pagedMeasurementStyle = "true";
+  style.textContent = [
+    documentBaseCss,
+    highlightCss,
+    katexCss,
+    themeCss,
+    documentGeometryCss
+  ].join("\n");
+
+  const host = documentRef.createElement("div");
+  host.dataset.pagedMeasurementHost = "true";
+  host.style.cssText = [
+    "position: fixed",
+    "left: -100000px",
+    "top: 0",
+    `width: ${pageContent.width}px`,
+    "height: auto",
+    "opacity: 0",
+    "pointer-events: none",
+    "contain: layout style paint"
+  ].join(";");
+
+  documentRef.head.append(style);
+  host.append(content);
+  documentRef.body.append(host);
+
+  return {
+    host,
+    restore() {
+      content.append(...Array.from(host.childNodes));
+      host.remove();
+      style.remove();
+    }
+  };
+}
+
 function applyPageNumbers(
   container: ParentNode,
   payload: PagedPreviewPayload,
@@ -233,16 +285,37 @@ export class PagedDocumentRuntime {
     const mermaidErrors = await this.renderMermaid(content, payload);
     const mermaidMs = performance.now() - mermaidStartedAt;
 
-    const mermaidFitStartedAt = performance.now();
-    fitOversizedMermaidToPage(content, payload.exportConfig);
-    const mermaidFitMs = performance.now() - mermaidFitStartedAt;
+    let mermaidFitMs = 0;
+    let mermaidConversionMs = 0;
+    if (content.querySelector(".mermaid svg")) {
+      const measurement = mountMeasurementContainer(
+        documentRef,
+        content,
+        payload,
+        options.target
+      );
+      try {
+        await documentRef.fonts.ready;
+        await waitForImages(measurement.host);
 
-    const mermaidConversionStartedAt = performance.now();
-    if (options.mermaidOutput === "svg-image") {
-      replaceMermaidSvgWithImages(content);
+        const mermaidFitStartedAt = performance.now();
+        fitOversizedMermaidToPage(
+          measurement.host,
+          payload.exportConfig
+        );
+        mermaidFitMs = performance.now() - mermaidFitStartedAt;
+
+        const mermaidConversionStartedAt = performance.now();
+        if (options.mermaidOutput === "svg-image") {
+          replaceMermaidSvgWithImages(measurement.host);
+          await waitForImages(measurement.host);
+        }
+        mermaidConversionMs =
+          performance.now() - mermaidConversionStartedAt;
+      } finally {
+        measurement.restore();
+      }
     }
-    const mermaidConversionMs =
-      performance.now() - mermaidConversionStartedAt;
 
     if (!shouldContinue()) {
       return undefined;