[api-minor] Move the page reference/number caching into the API

Rather than having to handle this *manually* throughout the viewer, this functionality can instead be moved into the API which simplifies the code slightly.

web/pdf_link_service.js

@@ -49,8 +49,6 @@ const LinkTarget = {
 class PDFLinkService {
   externalLinkEnabled = true;
 
-  #pagesRefCache = new Map();
-
   /**
    * @param {PDFLinkServiceOptions} options
    */
@@ -74,7 +72,6 @@ class PDFLinkService {
   setDocument(pdfDocument, baseUrl = null) {
     this.baseUrl = baseUrl;
     this.pdfDocument = pdfDocument;
-    this.#pagesRefCache.clear();
   }
 
   setViewer(pdfViewer) {
@@ -157,15 +154,14 @@ class PDFLinkService {
     // Dest array looks like that: <page-ref> </XYZ|/FitXXX> <args..>
     const [destRef] = explicitDest;
 
-    if (typeof destRef === "object" && destRef !== null) {
-      pageNumber = this._cachedPageNumber(destRef);
+    if (destRef && typeof destRef === "object") {
+      pageNumber = this.pdfDocument.cachedPageNumber(destRef);
 
       if (!pageNumber) {
         // Fetch the page reference if it's not yet available. This could
         // only occur during loading, before all pages have been resolved.
         try {
           pageNumber = (await this.pdfDocument.getPageIndex(destRef)) + 1;
-          this.cachePageRef(pageNumber, destRef);
         } catch {
           console.error(
             `goToDestination: "${destRef}" is not a valid page reference, for dest="${dest}".`
@@ -496,31 +492,6 @@ class PDFLinkService {
     );
   }
 
-  /**
-   * @param {number} pageNum - page number.
-   * @param {Object} pageRef - reference to the page.
-   */
-  cachePageRef(pageNum, pageRef) {
-    if (!pageRef) {
-      return;
-    }
-    const refStr =
-      pageRef.gen === 0 ? `${pageRef.num}R` : `${pageRef.num}R${pageRef.gen}`;
-    this.#pagesRefCache.set(refStr, pageNum);
-  }
-
-  /**
-   * @ignore
-   */
-  _cachedPageNumber(pageRef) {
-    if (!pageRef) {
-      return null;
-    }
-    const refStr =
-      pageRef.gen === 0 ? `${pageRef.num}R` : `${pageRef.num}R${pageRef.gen}`;
-    return this.#pagesRefCache.get(refStr) || null;
-  }
-
   static #isValidExplicitDest(dest) {
     if (!Array.isArray(dest) || dest.length < 2) {
       return false;
@@ -580,12 +551,6 @@ class PDFLinkService {
  */
 class SimpleLinkService extends PDFLinkService {
   setDocument(pdfDocument, baseUrl = null) {}
-
-  /**
-   * @param {number} pageNum - page number.
-   * @param {Object} pageRef - reference to the page.
-   */
-  cachePageRef(pageNum, pageRef) {}
 }
 
 export { LinkTarget, PDFLinkService, SimpleLinkService };