BL-15421 placeholders in thumbnails adding pages from template starter

src/BloomBrowserUI/placeHolderImages.less

@@ -37,9 +37,11 @@
     background-size: contain;
 }
 
-// When previewing in the Collection Tab, and also when in Change Layout mode in the Edit tab,
+// When previewing in the Collection Tab, and also when in Change Layout mode in the Edit tab, or when dealing with
+// freshly added pages that have not yet been touched by the Canvas Element Manager,
 // img elements may not always be wrapped in canvas-element divs (see BL-15514 and BL-15763). Also below.
 .preview,
+.bloom-templateThumbnail,
 .origami-layout-mode {
     .bloom-canvas:not(:has(.bloom-imageContainer)):has(
             img[src*="placeHolder.png"]

src/BloomExe/Book/Book.cs

@@ -645,26 +645,7 @@ public HtmlDom GetHtmlDomForPageList(HtmlDom inputDom)
             return result;
         }
 
-        public HtmlDom GetPreviewXmlDocumentForPage(IPage page)
-        {
-            if (HasFatalError)
-            {
-                return GetErrorDom();
-            }
-            var pageDom = GetHtmlDomWithJustOnePage(page);
-            pageDom.RemoveModeStyleSheets();
-            pageDom.EnsureStylesheetLinks(this.Storage.GetCssFilesToLinkForPreview());
-            // Note: it would be a fine enhancement here to first check for "branding-{flavor}.css",
-            // but we'll leave that until we need it.
-            AddPreviewJavascript(pageDom); //review: this is just for thumbnails... should we be having the javascript run?
-            return pageDom;
-        }
-
-        // Differs from GetPreviewXmlDocumentForPage() by not adding the three stylesheets
-        // adding them will full paths seems to be diastrous. I think cross-domain rules
-        // prevent them from being loaded, and so we lose the page size information, and the
-        // thumbs come out random sizes. Not sure why this isn't a problem in GetPreviewXmlDocumentForPage.
-        // Also, since this is used for thumbnails of template pages, we insert some arbitrary text
+        // Since this is used for thumbnails of template pages, we insert text placeholders (grey bars)
         // into empty editable divs to give a better idea of what a typical page will look like.
         internal HtmlDom GetThumbnailXmlDocumentForPage(IPage page)
         {
@@ -674,6 +655,7 @@ internal HtmlDom GetThumbnailXmlDocumentForPage(IPage page)
             }
             var pageDom = GetHtmlDomWithJustOnePage(page);
             AddPreviewJavascript(pageDom);
+            pageDom.EnsureStylesheetLinks(this.Storage.GetCssFilesToLinkForPreview());
             pageDom.Body.AddClass("bloom-templateThumbnail");
             return pageDom;
         }
@@ -2163,7 +2145,9 @@ private void CreateOrUpdateDefaultLangStyles()
                         {
                             var lang = line.Substring(kLangTag.Length, idxQuote - kLangTag.Length);
                             // Don't let empty language tag creep in (or stay in). (BL-15784)
-                            copyCurrentRule = !String.IsNullOrEmpty(lang) && !languagesWeAlreadyHave.Contains(lang);
+                            copyCurrentRule =
+                                !String.IsNullOrEmpty(lang)
+                                && !languagesWeAlreadyHave.Contains(lang);
                             languagesWeAlreadyHave.Add(lang); // don't copy if another css block has crept in.
                         }
                     }

src/BloomExe/BookThumbNailer.cs

@@ -383,7 +383,7 @@ Guid requestId
         ///   Currently used by the image server
         ///   to get thumbnails that are used in the add page dialog. Since this dialog can show
         ///   an enlarged version of the page, we generate these at a higher resolution than usual.
-        ///   Also, to make more realistic views of template pages we insert fake text wherever
+        ///   Also, to make more realistic views of template pages we insert text placeholders (grey bars) wherever
         ///   there is an empty edit block.
         ///
         ///   The result is cached for possible future use so the caller should not dispose of it.

src/BloomExe/Publish/PublishModel.cs

@@ -831,63 +831,6 @@ public void UpdateModelUponActivation()
                 _currentlyLoadedBook.EnsureUpToDate();
         }
 
-        public IEnumerable<HtmlDom> GetPageDoms()
-        {
-            if (BookSelection.CurrentSelection.IsFolio)
-            {
-                foreach (var bi in _currentBookCollectionSelection.CurrentSelection.GetBookInfos())
-                {
-                    var book = _bookServer.GetBookFromBookInfo(bi);
-                    //need to hide the "notes for illustrators" on SHRP, which is controlled by the layout
-                    book.SetLayout(
-                        new Layout()
-                        {
-                            SizeAndOrientation = SizeAndOrientation.FromString("B5Portrait"),
-                            Style = "HideProductionNotes",
-                        }
-                    );
-                    foreach (var page in book.GetPages())
-                    {
-                        //yield return book.GetPreviewXmlDocumentForPage(page);
-
-                        var previewXmlDocumentForPage = book.GetPreviewXmlDocumentForPage(page);
-                        BookStorage.SetBaseForRelativePaths(
-                            previewXmlDocumentForPage,
-                            book.FolderPath
-                        );
-
-                        AddStylesheetClasses(previewXmlDocumentForPage.RawDom);
-
-                        yield return previewXmlDocumentForPage;
-                    }
-                }
-            }
-            else //this one is just for testing, it's not especially fruitful to export for a single book
-            {
-                //need to hide the "notes for illustrators" on SHRP, which is controlled by the layout
-                BookSelection.CurrentSelection.SetLayout(
-                    new Layout()
-                    {
-                        SizeAndOrientation = SizeAndOrientation.FromString("B5Portrait"),
-                        Style = "HideProductionNotes",
-                    }
-                );
-
-                foreach (var page in BookSelection.CurrentSelection.GetPages())
-                {
-                    var previewXmlDocumentForPage =
-                        BookSelection.CurrentSelection.GetPreviewXmlDocumentForPage(page);
-                    //get the original images, not compressed ones (just in case the thumbnails are, like, full-size & they want quality)
-                    BookStorage.SetBaseForRelativePaths(
-                        previewXmlDocumentForPage,
-                        BookSelection.CurrentSelection.FolderPath
-                    );
-                    AddStylesheetClasses(previewXmlDocumentForPage.RawDom);
-                    yield return previewXmlDocumentForPage;
-                }
-            }
-        }
-
         /// <summary>
         /// Remove all text data that is not in a desired language.
         /// Keeps all xmatter data if shouldPruneXmatter is false; if it is true, keeps xmatter data in xmatterLangsToKeep.

src/content/bookLayout/basePage.less

@@ -114,6 +114,19 @@ div.bloomPlayer-page {
         display: none;
     }
 
+    // bloom-canvas-elements may have their height and width specified in a style attribute, and this size may not be
+    // right if we use a different paper size when making thumbnails for the add page dialog.
+    // And ReplaceAnyVideoElementsWithPlaceholder adds video placeholders without making them the right size.
+    // We want to override any such sizing and just blow all the placeholders up big so that the resulting thumbnail
+    // will show the user the layout of the page. We don't need precision here.
+    .bloom-imageContainer:has(img[src*="video-placeholder.svg"]),
+    .bloom-canvas-element.bloom-backgroundImage:has(
+            img[src*="placeHolder.png"]
+        ) {
+        height: 100% !important;
+        width: 100% !important;
+    }
+
     .bloom-translationGroup {
         // Height in ems so it is sensitive to font size. The '1 transparent/3 grey' here is not necessarily
         // ideal, and was just arrived at through experimentation, balancing accuracy