Introduce a "thumbnailrendered" event to simplify cleanup after thumbnail rendering (PR 12613 follow-up)

The way that the cleanup was implemented in PR 12613 has always bothered me slightly, since the `isPageCached`-method that I introduced there always felt quite out-of-place in the `IPDFLinkService`-implementations.
By introducing a new "thumbnailrendered" event, similar to the existing "pagerendered" one, we're able to move the cleanup handling into the `PDFViewer`-class instead.

web/app.js

@@ -533,6 +533,7 @@ const PDFViewerApplication = {
     if (appConfig.sidebar?.thumbnailView) {
       this.pdfThumbnailViewer = new PDFThumbnailViewer({
         container: appConfig.sidebar.thumbnailView,
+        eventBus,
         renderingQueue: pdfRenderingQueue,
         linkService: pdfLinkService,
         l10n: this.l10n,

web/interfaces.js

@@ -112,11 +112,6 @@ class IPDFLinkService {
    * @param {Object} pageRef - reference to the page.
    */
   cachePageRef(pageNum, pageRef) {}
-
-  /**
-   * @param {number} pageNumber
-   */
-  isPageCached(pageNumber) {}
 }
 
 /**

web/pdf_link_service.js

@@ -569,13 +569,6 @@ class PDFLinkService {
     return this.#pagesRefCache.get(refStr) || null;
   }
 
-  /**
-   * @param {number} pageNumber
-   */
-  isPageCached(pageNumber) {
-    return this.pdfViewer.isPageCached(pageNumber);
-  }
-
   static #isValidExplicitDestination(dest) {
     if (!Array.isArray(dest)) {
       return false;
@@ -737,13 +730,6 @@ class SimpleLinkService {
    * @param {Object} pageRef - reference to the page.
    */
   cachePageRef(pageNum, pageRef) {}
-
-  /**
-   * @param {number} pageNumber
-   */
-  isPageCached(pageNumber) {
-    return true;
-  }
 }
 
 export { LinkTarget, PDFLinkService, SimpleLinkService };

web/pdf_thumbnail_view.js

@@ -13,6 +13,7 @@
  * limitations under the License.
  */
 
+/** @typedef {import("./event_utils").EventBus} EventBus */
 /** @typedef {import("./interfaces").IL10n} IL10n */
 /** @typedef {import("./interfaces").IPDFLinkService} IPDFLinkService */
 /** @typedef {import("./interfaces").IRenderableView} IRenderableView */
@@ -29,6 +30,7 @@ const THUMBNAIL_WIDTH = 98; // px
 /**
  * @typedef {Object} PDFThumbnailViewOptions
  * @property {HTMLDivElement} container - The viewer element.
+ * @property {EventBus} eventBus - The application event bus.
  * @property {number} id - The thumbnail's unique ID (normally its number).
  * @property {PageViewport} defaultViewport - The page viewport.
  * @property {Promise<OptionalContentConfig>} [optionalContentConfigPromise] -
@@ -81,6 +83,7 @@ class PDFThumbnailView {
    */
   constructor({
     container,
+    eventBus,
     id,
     defaultViewport,
     optionalContentConfigPromise,
@@ -100,6 +103,7 @@ class PDFThumbnailView {
     this._optionalContentConfigPromise = optionalContentConfigPromise || null;
     this.pageColors = pageColors || null;
 
+    this.eventBus = eventBus;
     this.linkService = linkService;
     this.renderingQueue = renderingQueue;
 
@@ -314,12 +318,11 @@ class PDFThumbnailView {
       canvas.width = 0;
       canvas.height = 0;
 
-      // Only trigger cleanup, once rendering has finished, when the current
-      // pageView is *not* cached on the `BaseViewer`-instance.
-      const pageCached = this.linkService.isPageCached(this.id);
-      if (!pageCached) {
-        this.pdfPage?.cleanup();
-      }
+      this.eventBus.dispatch("thumbnailrendered", {
+        source: this,
+        pageNumber: this.id,
+        pdfPage: this.pdfPage,
+      });
     });
 
     return resultPromise;

web/pdf_thumbnail_viewer.js

@@ -14,6 +14,7 @@
  */
 
 /** @typedef {import("../src/display/api").PDFDocumentProxy} PDFDocumentProxy */
+/** @typedef {import("./event_utils").EventBus} EventBus */
 /** @typedef {import("./interfaces").IL10n} IL10n */
 /** @typedef {import("./interfaces").IPDFLinkService} IPDFLinkService */
 // eslint-disable-next-line max-len
@@ -35,6 +36,7 @@ const THUMBNAIL_SELECTED_CLASS = "selected";
  * @typedef {Object} PDFThumbnailViewerOptions
  * @property {HTMLDivElement} container - The container for the thumbnail
  *   elements.
+ * @property {EventBus} eventBus - The application event bus.
  * @property {IPDFLinkService} linkService - The navigation/linking service.
  * @property {PDFRenderingQueue} renderingQueue - The rendering queue object.
  * @property {IL10n} l10n - Localization service.
@@ -50,8 +52,16 @@ class PDFThumbnailViewer {
   /**
    * @param {PDFThumbnailViewerOptions} options
    */
-  constructor({ container, linkService, renderingQueue, l10n, pageColors }) {
+  constructor({
+    container,
+    eventBus,
+    linkService,
+    renderingQueue,
+    l10n,
+    pageColors,
+  }) {
     this.container = container;
+    this.eventBus = eventBus;
     this.linkService = linkService;
     this.renderingQueue = renderingQueue;
     this.l10n = l10n;
@@ -209,6 +219,7 @@ class PDFThumbnailViewer {
         for (let pageNum = 1; pageNum <= pagesCount; ++pageNum) {
           const thumbnail = new PDFThumbnailView({
             container: this.container,
+            eventBus: this.eventBus,
             id: pageNum,
             defaultViewport: viewport.clone(),
             optionalContentConfigPromise,

web/pdf_viewer.js

@@ -322,6 +322,15 @@ class PDFViewer {
     }
 
     this.#updateContainerHeightCss();
+
+    // Trigger API-cleanup, once thumbnail rendering has finished,
+    // if the relevant pageView is *not* cached in the buffer.
+    this.eventBus._on("thumbnailrendered", ({ pageNumber, pdfPage }) => {
+      const pageView = this._pages[pageNumber - 1];
+      if (!this.#buffer.has(pageView)) {
+        pdfPage?.cleanup();
+      }
+    });
   }
 
   get pagesCount() {
@@ -1645,27 +1654,6 @@ class PDFViewer {
     });
   }
 
-  /**
-   * @param {number} pageNumber
-   */
-  isPageCached(pageNumber) {
-    if (!this.pdfDocument) {
-      return false;
-    }
-    if (
-      !(
-        Number.isInteger(pageNumber) &&
-        pageNumber > 0 &&
-        pageNumber <= this.pagesCount
-      )
-    ) {
-      console.error(`isPageCached: "${pageNumber}" is not a valid page.`);
-      return false;
-    }
-    const pageView = this._pages[pageNumber - 1];
-    return this.#buffer.has(pageView);
-  }
-
   cleanup() {
     for (const pageView of this._pages) {
       if (pageView.renderingState !== RenderingStates.FINISHED) {