Fix memory leak when closing the EPUB navigator before the content is loaded

Author: mickael-menu

Sources/Navigator/EPUB/EPUBReflowableSpreadView.swift

@@ -33,6 +33,16 @@ final class EPUBReflowableSpreadView: EPUBSpreadView {
         )
     }
 
+    override func clear() {
+        super.clear()
+
+        // Clean up go to continuations.
+        for continuation in goToContinuations {
+            continuation.resume()
+        }
+        goToContinuations.removeAll()
+    }
+
     override func setupWebView() {
         super.setupWebView()
 
@@ -193,7 +203,6 @@ final class EPUBReflowableSpreadView: EPUBSpreadView {
     // Location to scroll to in the resource once the page is loaded.
     private var pendingLocation: PageLocation = .start
 
-    @MainActor
     override func go(to location: PageLocation) async {
         guard isSpreadLoaded else {
             // Delays moving to the location until the document is loaded.
@@ -215,22 +224,19 @@ final class EPUBReflowableSpreadView: EPUBSpreadView {
         didCompleteGoTo()
     }
 
-    @MainActor
     private func waitGoToCompletion() async {
         await withCheckedContinuation { continuation in
             goToContinuations.append(continuation)
         }
     }
 
-    @MainActor
     private func didCompleteGoTo() {
         for cont in goToContinuations {
             cont.resume()
         }
         goToContinuations.removeAll()
     }
 
-    @MainActor
     private var goToContinuations: [CheckedContinuation<Void, Never>] = []
 
     @discardableResult

Sources/Navigator/EPUB/EPUBSpreadView.swift

@@ -95,6 +95,13 @@ class EPUBSpreadView: UIView, Loggable, PageView {
 
     deinit {
         NotificationCenter.default.removeObserver(self)
+        clear()
+    }
+
+    /// Called when the spread view is removed from the view hierarchy, to
+    /// clear pending operations and retain cycles.
+    func clear() {
+        // Disable JS messages to break WKUserContentController reference.
         disableJSMessages()
     }
 
@@ -126,14 +133,18 @@ class EPUBSpreadView: UIView, Loggable, PageView {
         webView.scrollView
     }
 
+    override func willMove(toSuperview newSuperview: UIView?) {
+        super.willMove(toSuperview: newSuperview)
+
+        if newSuperview == nil {
+            clear()
+        }
+    }
+
     override func didMoveToSuperview() {
         super.didMoveToSuperview()
 
-        if superview == nil {
-            disableJSMessages()
-            // Fixing an iOS 9 bug by explicitly clearing scrollView.delegate before deinitialization
-            scrollView.delegate = nil
-        } else {
+        if superview != nil {
             enableJSMessages()
             scrollView.delegate = self
         }

Sources/Navigator/Toolkit/PaginationView.swift

@@ -150,6 +150,18 @@ final class PaginationView: UIView, Loggable {
         scrollView.contentOffset.x = xOffsetForIndex(currentIndex)
     }
 
+    override func willMove(toSuperview newSuperview: UIView?) {
+        super.willMove(toSuperview: newSuperview)
+
+        if newSuperview == nil {
+            // Remove all spread views to break retain cycles
+            for (_, view) in loadedViews {
+                view.removeFromSuperview()
+            }
+            loadedViews.removeAll()
+        }
+    }
+
     override func didMoveToWindow() {
         super.didMoveToWindow()