Make sure the focus moves on the first page of the added pdf after a merge (bug 2034827)

test/integration/reorganize_pages_spec.mjs

@@ -3084,6 +3084,12 @@ describe("Reorganize Pages View", () => {
             () => parseInt(document.getElementById("pageNumber").max, 10) === 6
           );
 
+          // Focus must move to the first newly inserted page (page 3, since
+          // we merged after page 2).
+          await page.waitForFunction(
+            () => window.PDFViewerApplication.page === 3
+          );
+
           // Pages 1–2 come from the original document, then all 3 pages of
           // the merged PDF, then pages 4–6 of the original shifted to the end.
           await waitForHavingContents(page, [1, 2, 1, 2, 3, 3]);

web/app.js

@@ -1874,7 +1874,8 @@ const PDFViewerApplication = {
     }
     this.pdfHistory.initialize({
       fingerprint,
-      resetHistory: viewOnLoad === ViewOnLoad.INITIAL,
+      resetHistory:
+        viewOnLoad === ViewOnLoad.INITIAL || !!this._mergedDocumentNeedsSaving,
       updateUrl: AppOptions.get("historyUpdateUrl"),
     });
 
@@ -2440,6 +2441,7 @@ const PDFViewerApplication = {
       return;
     }
     this._mergedDocumentNeedsSaving = true;
+
     this.open({
       data: modifiedPdfBytes,
       filename: this._docFilename,

web/pdf_thumbnail_viewer.js

@@ -338,7 +338,7 @@ class PDFThumbnailViewer {
             insertAfter: currentPageIndex ?? -1,
           });
           this.eventBus._on(
-            "thumbnailsloaded",
+            "pagesloaded",
             () => {
               // Clear any pre-merge selection: thumbnails are rebuilt fresh
               // (all unchecked), so the old set would cause a label/visual
@@ -358,7 +358,10 @@ class PDFThumbnailViewer {
                 this.#selectPage(i + 1, true);
               }
               if (insertedPagesCount) {
-                this.#updateCurrentPage(currentPageIndex + 2);
+                this.#updateCurrentPage(
+                  currentPageIndex + 2,
+                  /* force = */ true
+                );
               }
             },
             { once: true }