Convert the thumbnail view(er) code to use proper private methods

This allows us to get rid of the `@private` JSDoc comments, which were
used to convey intent back when proper private methods could not be used
yet in JavaScript. This improves code readability/maintenance and enables
better usage validation by tooling such as ESlint.

web/pdf_thumbnail_view.js

@@ -55,7 +55,7 @@ class TempImageFactory {
     tempCanvas.height = height;
 
     // Since this is a temporary canvas, we need to fill it with a white
-    // background ourselves. `_getPageDrawContext` uses CSS rules for this.
+    // background ourselves. `#getPageDrawContext` uses CSS rules for this.
     const ctx = tempCanvas.getContext("2d", { alpha: false });
     ctx.save();
     ctx.fillStyle = "rgb(255, 255, 255)";
@@ -196,10 +196,7 @@ class PDFThumbnailView {
     this.resume = null;
   }
 
-  /**
+  #getPageDrawContext(upscaleFactor = 1) {
-   * @private
-   */
-  _getPageDrawContext(upscaleFactor = 1) {
     // Keep the no-thumbnail outline visible, i.e. `data-loaded === false`,
     // until rendering/image conversion is complete, to avoid display issues.
     const canvas = document.createElement("canvas");
@@ -216,14 +213,11 @@ class PDFThumbnailView {
     return { ctx, canvas, transform };
   }
 
-  /**
+  #convertCanvasToImage(canvas) {
-   * @private
-   */
-  _convertCanvasToImage(canvas) {
     if (this.renderingState !== RenderingStates.FINISHED) {
-      throw new Error("_convertCanvasToImage: Rendering has not finished.");
+      throw new Error("#convertCanvasToImage: Rendering has not finished.");
     }
-    const reducedCanvas = this._reduceImage(canvas);
+    const reducedCanvas = this.#reduceImage(canvas);
 
     const image = document.createElement("img");
     image.className = "thumbnailImage";
@@ -253,7 +247,7 @@ class PDFThumbnailView {
       return;
     }
     this.renderingState = RenderingStates.FINISHED;
-    this._convertCanvasToImage(canvas);
+    this.#convertCanvasToImage(canvas);
 
     if (error) {
       throw error;
@@ -280,7 +274,7 @@ class PDFThumbnailView {
     // NOTE: To primarily avoid increasing memory usage too much, but also to
     //   reduce downsizing overhead, we purposely limit the up-scaling factor.
     const { ctx, canvas, transform } =
-      this._getPageDrawContext(DRAW_UPSCALE_FACTOR);
+      this.#getPageDrawContext(DRAW_UPSCALE_FACTOR);
     const drawViewport = this.viewport.clone({
       scale: DRAW_UPSCALE_FACTOR * this.scale,
     });
@@ -342,14 +336,11 @@ class PDFThumbnailView {
       return;
     }
     this.renderingState = RenderingStates.FINISHED;
-    this._convertCanvasToImage(canvas);
+    this.#convertCanvasToImage(canvas);
   }
 
-  /**
+  #reduceImage(img) {
-   * @private
+    const { ctx, canvas } = this.#getPageDrawContext();
-   */
-  _reduceImage(img) {
-    const { ctx, canvas } = this._getPageDrawContext();
 
     if (img.width <= 2 * canvas.width) {
       ctx.drawImage(

web/pdf_thumbnail_viewer.js

@@ -64,14 +64,11 @@ class PDFThumbnailViewer {
     this.renderingQueue = renderingQueue;
     this.pageColors = pageColors || null;
 
-    this.scroll = watchScroll(this.container, this._scrollUpdated.bind(this));
+    this.scroll = watchScroll(this.container, this.#scrollUpdated.bind(this));
-    this._resetView();
+    this.#resetView();
   }
 
-  /**
+  #scrollUpdated() {
-   * @private
-   */
-  _scrollUpdated() {
     this.renderingQueue.renderHighestPriority();
   }
 
@@ -79,10 +76,7 @@ class PDFThumbnailViewer {
     return this._thumbnails[index];
   }
 
-  /**
+  #getVisibleThumbs() {
-   * @private
-   */
-  _getVisibleThumbs() {
     return getVisibleElements({
       scrollEl: this.container,
       views: this._thumbnails,
@@ -107,7 +101,7 @@ class PDFThumbnailViewer {
       // ... and add the highlight to the new thumbnail.
       thumbnailView.div.classList.add(THUMBNAIL_SELECTED_CLASS);
     }
-    const { first, last, views } = this._getVisibleThumbs();
+    const { first, last, views } = this.#getVisibleThumbs();
 
     // If the thumbnail isn't currently visible, scroll it into view.
     if (views.length > 0) {
@@ -162,10 +156,7 @@ class PDFThumbnailViewer {
     TempImageFactory.destroyCanvas();
   }
 
-  /**
+  #resetView() {
-   * @private
-   */
-  _resetView() {
     this._thumbnails = [];
     this._currentPageNumber = 1;
     this._pageLabels = null;
@@ -180,8 +171,8 @@ class PDFThumbnailViewer {
    */
   setDocument(pdfDocument) {
     if (this.pdfDocument) {
-      this._cancelRendering();
+      this.#cancelRendering();
-      this._resetView();
+      this.#resetView();
     }
 
     this.pdfDocument = pdfDocument;
@@ -225,10 +216,7 @@ class PDFThumbnailViewer {
       });
   }
 
-  /**
+  #cancelRendering() {
-   * @private
-   */
-  _cancelRendering() {
     for (const thumbnail of this._thumbnails) {
       thumbnail.cancelRendering();
     }
@@ -287,7 +275,7 @@ class PDFThumbnailViewer {
   }
 
   forceRendering() {
-    const visibleThumbs = this._getVisibleThumbs();
+    const visibleThumbs = this.#getVisibleThumbs();
     const scrollAhead = this.#getScrollAhead(visibleThumbs);
     const thumbView = this.renderingQueue.getHighestPriority(
       visibleThumbs,