Provide the position of some elements when the dimensions of the viewport are updated (bug 1907890)

web/app.js

@@ -178,6 +178,7 @@ const PDFViewerApplication = {
   _nimbusDataPromise: null,
   _caretBrowsing: null,
   _isScrolling: false,
+  _idsToWatchOutPromise: null,
 
   // Called once when the document is loaded.
   async initialize(appConfig) {
@@ -187,6 +188,7 @@ const PDFViewerApplication = {
     if (typeof PDFJSDev !== "undefined" && !PDFJSDev.test("GENERIC")) {
       l10nPromise = this.externalServices.createL10n();
       if (PDFJSDev.test("MOZCENTRAL")) {
+        this._idsToWatchOutPromise = this.externalServices.getIdsToWatchOut();
         this._allowedGlobalEventsPromise =
           this.externalServices.getGlobalEventNames();
       }
@@ -486,6 +488,7 @@ const PDFViewerApplication = {
       mlManager: this.mlManager,
       abortSignal: this._globalAbortController.signal,
       enableHWA,
+      idsToWatchOutPromise: this._idsToWatchOutPromise,
     });
     this.pdfViewer = pdfViewer;
 

web/external_services.js

@@ -52,6 +52,8 @@ class BaseExternalServices {
   }
 
   dispatchGlobalEvent(_event) {}
+
+  async getIdsToWatchOut() {}
 }
 
 export { BaseExternalServices };

web/firefoxcom.js

@@ -425,6 +425,10 @@ class ExternalServices extends BaseExternalServices {
   dispatchGlobalEvent(event) {
     FirefoxCom.request("dispatchGlobalEvent", event);
   }
+
+  async getIdsToWatchOut() {
+    return FirefoxCom.requestAsync("getIdsToWatchOut", null);
+  }
 }
 
 export { DownloadManager, ExternalServices, initCom, MLManager, Preferences };

web/pdf_viewer.js

@@ -68,6 +68,7 @@ import { PDFRenderingQueue } from "./pdf_rendering_queue.js";
 import { SimpleLinkService } from "./pdf_link_service.js";
 
 const DEFAULT_CACHE_SIZE = 10;
+const UPDATE_ELEMENTS_RECT_DELAY = 100;
 
 const PagesCountLimit = {
   FORCE_SCROLL_MODE_PAGE: 10000,
@@ -233,6 +234,10 @@ class PDFViewer {
 
   #hiddenCopyElement = null;
 
+  #idsToWatchOutPromise = null;
+
+  #updateElementsRectTimeoutId = null;
+
   #interruptCopyCondition = false;
 
   #previousContainerHeight = 0;
@@ -308,6 +313,7 @@ class PDFViewer {
     this.pageColors = options.pageColors || null;
     this.#mlManager = options.mlManager || null;
     this.#enableHWA = options.enableHWA || false;
+    this.#idsToWatchOutPromise = options.idsToWatchOutPromise || null;
 
     this.defaultRenderingQueue = !options.renderingQueue;
     if (
@@ -2246,12 +2252,32 @@ class PDFViewer {
     }
   }
 
+  #updateElementsRect() {
+    this.#idsToWatchOutPromise?.then(ids => {
+      if (!ids?.length) {
+        this.#idsToWatchOutPromise = null;
+        return;
+      }
+      clearTimeout(this.#updateElementsRectTimeoutId);
+      this.#updateElementsRectTimeoutId = setTimeout(() => {
+        const detail = Object.create(null);
+        for (const id of ids) {
+          detail[id] = document.getElementById(id).getBoundingClientRect();
+        }
+        this.eventBus.dispatch("updateelementsposition", {
+          detail,
+        });
+      }, UPDATE_ELEMENTS_RECT_DELAY);
+    });
+  }
+
   #resizeObserverCallback(entries) {
     for (const entry of entries) {
       if (entry.target === this.container) {
         this.#updateContainerHeightCss(
           Math.floor(entry.borderBoxSize[0].blockSize)
         );
+        this.#updateElementsRect();
         this.#containerTopLeft = null;
         break;
       }