readium · mickael-menu · Jan 15, 2026 · Jan 14, 2026 · Jan 15, 2026 · Jan 15, 2026
diff --git a/.github/workflows/checks.yml b/.github/workflows/checks.yml
@@ -7,9 +7,9 @@ on:
 
 env:
   platform: ${{ 'iOS Simulator' }}
-  device: ${{ 'iPhone SE (3rd generation)' }}
+  device: ${{ 'iPhone 17' }}
   commit_sha: ${{ github.sha }}
-  DEVELOPER_DIR: /Applications/Xcode_16.3.app/Contents/Developer
+  DEVELOPER_DIR: /Applications/Xcode_16.4.app/Contents/Developer
 
 jobs:
   build:

diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -9,10 +9,26 @@ All notable changes to this project will be documented in this file. Take a look
 #### Navigator
 
 * Support for displaying Divina (image-based publications like CBZ) in the fixed-layout EPUB navigator.
+* Bitmap images in the EPUB reading order are now supported as a fixed layout resource.
 
 #### Streamer
 
 * The `ImageParser` now extracts metadata from `ComicInfo.xml` files in CBZ archives.
+* EPUB manifest item fallbacks are now exposed as `alternates` in the corresponding `Link`.
+* EPUBs with only bitmap images in the spine are now treated as Divina publications with fixed layout.
+    * When an EPUB spine item is HTML with a bitmap image fallback (or vice versa), the image is preferred as the primary link.
+
+### Deprecated
+
+#### Streamer
+
+* The EPUB manifest item `id` attribute is no longer exposed in `Link.properties`.
+
+### Fixed
+
+#### Navigator
+
+* PDF documents are now opened off the main thread, preventing UI freezes with large files.
 
 
 ## [3.6.0]

diff --git a/Sources/Navigator/EPUB/Assets/Static/scripts/readium-fixed-wrapper-one.js b/Sources/Navigator/EPUB/Assets/Static/scripts/readium-fixed-wrapper-one.js
diff --git a/Sources/Navigator/EPUB/Assets/Static/scripts/readium-fixed-wrapper-two.js b/Sources/Navigator/EPUB/Assets/Static/scripts/readium-fixed-wrapper-two.js
diff --git a/Sources/Navigator/EPUB/Scripts/src/fixed-page.js b/Sources/Navigator/EPUB/Scripts/src/fixed-page.js
@@ -156,6 +156,15 @@ export function FixedPage(iframeId, pageType) {
     viewport.content = "initial-scale=" + scale + ", minimum-scale=" + scale;
   }
 
+  // Sets the iframe source URL.
+  function setIframeSrc(url) {
+    // Release the memory of a previously created blob URL, if needed.
+    if (_iframe.src.startsWith("blob:")) {
+      URL.revokeObjectURL(_iframe.src);
+    }
+    _iframe.src = url;
+  }
+
   return {
     // Returns whether the page is currently loading its contents.
     isLoading: false,
@@ -194,17 +203,20 @@ export function FixedPage(iframeId, pageType) {
       }
 
       _iframe.addEventListener("load", loaded);
-      _iframe.src = resource.url;
+
+      var url = resourceUrl(resource);
+      setIframeSrc(url);
     },
 
-    // Resets the page and empty its contents.
+    // Resets the page and empties its contents.
     reset: function () {
       if (!this.link) {
         return;
       }
       this.link = null;
       _pageSize = null;
-      _iframe.src = "about:blank";
+
+      setIframeSrc("about:blank");
     },
 
     // Evaluates a script in the context of the page.
@@ -236,3 +248,46 @@ export function FixedPage(iframeId, pageType) {
     },
   };
 }
+
+// Returns the URL to load for the given resource.
+// Bitmap images are wrapped in an HTML document with alt text for accessibility.
+function resourceUrl(resource) {
+  if (isBitmapMediaType(resource.link.type)) {
+    let html = generateImageWrapper(resource.url, resource.link.title);
+    let blob = new Blob([html], { type: "text/html" });
+    return URL.createObjectURL(blob);
+  } else {
+    return resource.url;
+  }
+}
+
+// Helper to detect bitmap media types.
+function isBitmapMediaType(type) {
+  if (!type) return false;
+  return type.startsWith("image/") && !type.includes("svg");
+}
+
+// Generate an HTML wrapper with alt text for the bitmap at `imageUrl`.
+function generateImageWrapper(imageUrl, altText) {
+  let doc = document.implementation.createHTMLDocument("");
+
+  let meta = doc.createElement("meta");
+  meta.name = "viewport";
+  meta.content = "width=device-width, height=device-height";
+  doc.head.appendChild(meta);
+
+  let style = doc.createElement("style");
+  style.textContent =
+    "body { margin: 0; }\n" +
+    "img { display: block; width: 100%; height: 100%; object-fit: contain; }";
+  doc.head.appendChild(style);
+
+  let img = doc.createElement("img");
+  img.src = imageUrl;
+  if (altText) {
+    img.alt = altText;
+  }
+  doc.body.appendChild(img);
+
+  return "<!DOCTYPE html>\n" + doc.documentElement.outerHTML;
+}
diff --git a/Sources/Navigator/PDF/PDFNavigatorViewController.swift b/Sources/Navigator/PDF/PDFNavigatorViewController.swift
@@ -455,7 +455,7 @@ open class PDFNavigatorViewController:
         }
 
         if currentResourceIndex != index {
-            guard let document = PDFDocument(url: url.url) else {
+            guard let document = await makeDocument(at: url) else {
                 log(.error, "Can't open PDF document at \(url)")
                 return false
             }
@@ -483,6 +483,13 @@ open class PDFNavigatorViewController:
         return true
     }
 
+    private func makeDocument(at url: AbsoluteURL) async -> PDFKit.PDFDocument? {
+        let task = Task.detached(priority: .userInitiated) {
+            PDFDocument(url: url.url)
+        }
+        return await task.value
+    }
+
     /// Updates the scale factors to match the currently visible pages.
     ///
     /// - Parameter zoomToFit: When true, the document will be zoomed to fit the

diff --git a/Sources/Shared/Publication/Manifest.swift b/Sources/Shared/Publication/Manifest.swift
@@ -120,7 +120,7 @@ public struct Manifest: JSONEquatable, Hashable, Sendable {
         case .epub:
             // EPUB needs to be explicitly indicated in `conformsTo`, otherwise
             // it could be a regular Web Publication.
-            return readingOrder.allAreHTML && metadata.conformsTo.contains(.epub)
+            return metadata.conformsTo.contains(.epub)
         case .pdf:
             return readingOrder.allMatchingMediaType(.pdf)
         default:

diff --git a/Sources/Streamer/Parser/EPUB/EPUBManifestParser.swift b/Sources/Streamer/Parser/EPUB/EPUBManifestParser.swift
@@ -21,11 +21,10 @@ final class EPUBManifestParser {
 
         // Extracts metadata and links from the OPF.
         let opfPackage = try await OPFParser(container: container, opfHREF: opfHREF, encryptions: encryptions).parsePublication()
-        let metadata = opfPackage.metadata
         let links = opfPackage.readingOrder + opfPackage.resources
 
         var manifest = await Manifest(
-            metadata: metadata,
+            metadata: opfPackage.metadata,
             readingOrder: opfPackage.readingOrder,
             resources: opfPackage.resources,
             subcollections: parseCollections(in: container, package: opfPackage, links: links)