Improve and simplify the PdfTextExtractor implementation

Working on PR 20784, I couldn't help noticing that this code can be improved a little bit.

 - Only initialize `PdfTextExtractor` in development mode and MOZCENTRAL builds, since it's unused elsewhere.

 - Re-factor how `PdfTextExtractor` waits for the viewer to be available/ready, by using existing (internal) events.
   This simplifies the `PdfTextExtractor` class and removes its `setViewer` method, which improves general consistency since normally the viewer-components don't use such a method in that way (here it was effectively used as a stand-in for a `setDocument` method).

 - Finally, while slightly unrelated, rename the `#getAllTextInProgress` field in the `PDFViewer` class to `#copyAllInProgress` to clearly indicate what it's for since the `getAllText` method is used more generally now.

web/app.js

@@ -264,8 +264,6 @@ const PDFViewerApplication = {
     }
     await this._initializeViewerComponents();
 
-    this.pdfTextExtractor = new PdfTextExtractor(this.externalServices);
-
     // Bind the various event handlers *after* the viewer has been
     // initialized, to prevent errors if an event arrives too soon.
     this.bindEvents();
@@ -779,6 +777,17 @@ const PDFViewerApplication = {
         );
       };
     }
+
+    if (
+      typeof PDFJSDev === "undefined" ||
+      PDFJSDev.test("TESTING || MOZCENTRAL")
+    ) {
+      this.pdfTextExtractor = new PdfTextExtractor(
+        externalServices,
+        pdfViewer,
+        eventBus
+      );
+    }
   },
 
   async run(config) {
@@ -1151,7 +1160,6 @@ const PDFViewerApplication = {
       this.pdfViewer.setDocument(null);
       this.pdfLinkService.setDocument(null);
       this.pdfDocumentProperties?.setDocument(null);
-      this.pdfTextExtractor?.setViewer(null);
     }
     this.pdfLinkService.externalLinkEnabled = true;
     this.store = null;
@@ -1455,7 +1463,6 @@ const PDFViewerApplication = {
 
     const pdfViewer = this.pdfViewer;
     pdfViewer.setDocument(pdfDocument);
-    this.pdfTextExtractor.setViewer(pdfViewer);
     const { firstPagePromise, onePageRendered, pagesPromise } = pdfViewer;
 
     this.pdfThumbnailViewer?.setDocument(pdfDocument);

web/pdf_text_extractor.js

@@ -18,55 +18,42 @@
  * and passing it back to the external service.
  */
 class PdfTextExtractor {
-  /** @type {PDFViewer} */
-  #pdfViewer;
-
+  /** @type {BaseExternalServices} */
   #externalServices;
 
-  /**
-   * @type {?Promise<string>}
-   */
+  /** @type {?Promise<string>} */
   #textPromise;
 
-  #pendingRequests = new Set();
+  #capability = Promise.withResolvers();
 
-  constructor(externalServices) {
+  constructor(externalServices, pdfViewer, eventBus) {
     this.#externalServices = externalServices;
 
+    eventBus._on("pagesinit", () => {
+      this.#capability.resolve(pdfViewer);
+    });
+    eventBus._on("pagesdestroy", () => {
+      this.#capability.reject(new Error("pagesdestroy"));
+      this.#textPromise = null;
+
+      this.#capability = Promise.withResolvers();
+    });
+
     window.addEventListener("requestTextContent", ({ detail }) => {
       this.extractTextContent(detail.requestId);
     });
   }
 
-  /**
-   * The PDF viewer is required to get the page text.
-   *
-   * @param {PDFViewer | null}
-   */
-  setViewer(pdfViewer) {
-    this.#pdfViewer = pdfViewer;
-    if (this.#pdfViewer && this.#pendingRequests.size) {
-      // Handle any pending requests that came in while things were loading.
-      for (const pendingRequest of this.#pendingRequests) {
-        this.extractTextContent(pendingRequest);
-      }
-      this.#pendingRequests.clear();
-    }
-  }
-
   /**
    * Builds up all of the text from a PDF.
    *
    * @param {number} requestId
    */
   async extractTextContent(requestId) {
-    if (!this.#pdfViewer) {
-      this.#pendingRequests.add(requestId);
-      return;
-    }
-
     if (!this.#textPromise) {
-      const textPromise = (this.#textPromise = this.#pdfViewer.getAllText());
+      const textPromise = (this.#textPromise = this.#capability.promise.then(
+        pdfViewer => pdfViewer.getAllText()
+      ));
 
       // After the text resolves, cache the text for a little bit in case
       // multiple consumers call it.

web/pdf_viewer.js

@@ -268,7 +268,7 @@ class PDFViewer {
 
   #switchAnnotationEditorModeTimeoutId = null;
 
-  #getAllTextInProgress = false;
+  #copyAllInProgress = false;
 
   #hiddenCopyElement = null;
 
@@ -816,13 +816,13 @@ class PDFViewer {
       //    has been selected.
 
       if (
-        this.#getAllTextInProgress ||
+        this.#copyAllInProgress ||
         textLayerMode === TextLayerMode.ENABLE_PERMISSIONS
       ) {
         stopEvent(event);
         return;
       }
-      this.#getAllTextInProgress = true;
+      this.#copyAllInProgress = true;
 
       // TODO: if all the pages are rendered we don't need to wait for
       // getAllText and we could just get text from the Selection object.
@@ -855,7 +855,7 @@ class PDFViewer {
           );
         })
         .finally(() => {
-          this.#getAllTextInProgress = false;
+          this.#copyAllInProgress = false;
           keydownAC.abort();
           classList.remove("copyAll");
         });