Merge pull request #16507 from Snuffleupagus/zooming-regressions-2

Fix more regressions from PR 15812

web/pdf_page_view.js

@@ -125,6 +125,7 @@ class PDFPageView {
   #textLayerMode = TextLayerMode.ENABLE;
 
   #useThumbnailCanvas = {
+    directDrawing: true,
     initialOptionalContent: true,
     regularAnnotations: true,
   };
@@ -552,6 +553,7 @@ class PDFPageView {
           optionalContentConfig.hasInitialVisibility;
       });
     }
+    this.#useThumbnailCanvas.directDrawing = true;
 
     const totalRotation = (this.rotation + this.pdfPageRotate) % 360;
     this.viewport = this.viewport.clone({
@@ -605,6 +607,9 @@ class PDFPageView {
           // the rendering state to INITIAL, hence the next call to
           // PDFViewer.update() will trigger a redraw (if it's mandatory).
           this.renderingState = RenderingStates.FINISHED;
+          // Ensure that the thumbnails won't become partially (or fully) blank,
+          // if the sidebar is opened before the actual rendering is done.
+          this.#useThumbnailCanvas.directDrawing = false;
         }
 
         this.cssTransform({
@@ -616,6 +621,11 @@ class PDFPageView {
           hideTextLayer: postponeDrawing,
         });
 
+        if (postponeDrawing) {
+          // The "pagerendered"-event will be dispatched once the actual
+          // rendering is done, hence don't dispatch it here as well.
+          return;
+        }
         this.eventBus.dispatch("pagerendered", {
           source: this,
           pageNumber: this.id,
@@ -1028,9 +1038,11 @@ class PDFPageView {
    * @ignore
    */
   get thumbnailCanvas() {
-    const { initialOptionalContent, regularAnnotations } =
+    const { directDrawing, initialOptionalContent, regularAnnotations } =
       this.#useThumbnailCanvas;
-    return initialOptionalContent && regularAnnotations ? this.canvas : null;
+    return directDrawing && initialOptionalContent && regularAnnotations
+      ? this.canvas
+      : null;
   }
 }