Fix issue loading fixed-layout EPUBs (#493)

CHANGELOG.md

@@ -11,6 +11,7 @@ All notable changes to this project will be documented in this file. Take a look
 #### Navigator
 
 * [#459](https://github.com/readium/swift-toolkit/issues/459) Fixed the stack overflow issue that occurred when running the text-to-speech on an EPUB file with many empty resources.
+* [#490](https://github.com/readium/swift-toolkit/issues/490) Fixed issue loading fixed-layout EPUBs.
 
 
 ## [3.0.0-alpha.2]

Sources/Navigator/EPUB/EPUBFixedSpreadView.swift

@@ -108,6 +108,7 @@ final class EPUBFixedSpreadView: EPUBSpreadView {
     }
 
     override func evaluateScript(_ script: String, inHREF href: AnyURL? = nil) async -> Result<Any, any Error> {
+        await spreadLoaded()
         let href = href?.string ?? ""
         let script = "spread.eval('\(href)', `\(script.replacingOccurrences(of: "\\", with: "\\\\").replacingOccurrences(of: "`", with: "\\`"))`);"
         return await super.evaluateScript(script)

Sources/Navigator/EPUB/EPUBNavigatorViewController.swift

@@ -347,7 +347,7 @@ open class EPUBNavigatorViewController: UIViewController,
 
         applySettings()
 
-        await reloadSpreads(at: currentLocation, force: false)
+        await _reloadSpreads(at: currentLocation, force: false)
 
         onInitializedCallbacks.complete()
     }
@@ -536,11 +536,11 @@ open class EPUBNavigatorViewController: UIViewController,
     private var reloadSpreadsContinuations = [CheckedContinuation<Void, Never>]()
     private var needsReloadSpreads = false
 
-    @MainActor
     private func reloadSpreads(at locator: Locator? = nil, force: Bool) async {
-        guard isViewLoaded else {
+        guard state != .initializing, isViewLoaded else {
             return
         }
+
         guard !needsReloadSpreads else {
             await withCheckedContinuation { continuation in
                 reloadSpreadsContinuations.append(continuation)

Sources/Navigator/EPUB/EPUBSpreadView.swift

@@ -234,13 +234,33 @@ class EPUBSpreadView: UIView, Loggable, PageView {
         applySettings()
         spreadDidLoad()
         delegate?.spreadViewDidLoad(self)
+        onSpreadLoadedCallbacks.complete()
     }
 
     /// To be overriden to customize the behavior after the spread is loaded.
     func spreadDidLoad() {
         showSpread()
     }
 
+    private let onSpreadLoadedCallbacks = CompletionList()
+
+    /// Awaits for the spread to be fully loaded.
+    func spreadLoaded() async {
+        await withCheckedContinuation { continuation in
+            whenSpreadLoaded {
+                continuation.resume()
+            }
+        }
+    }
+
+    /// Executes the given `callback` when the spread is fully loaded.
+    func whenSpreadLoaded(_ callback: @escaping () -> Void) {
+        let callback = onSpreadLoadedCallbacks.add(callback)
+        if spreadLoaded {
+            callback()
+        }
+    }
+
     func showSpread() {
         trace()
         activityIndicatorView?.stopAnimating()

Sources/Navigator/EPUB/Scripts/src/utils.js

@@ -83,6 +83,10 @@ function update(position) {
 window.addEventListener("scroll", onScroll);
 
 function onScroll() {
+  if (readium.isFixedLayout) {
+    return;
+  }
+
   last_known_scrollY_position =
     window.scrollY / document.scrollingElement.scrollHeight;
   // Using Math.abs because for RTL books, the value will be negative.