Swizzle WKWebView to fix scroll indicator in dark mode

Reader/AppDelegate.swift

@@ -6,15 +6,15 @@
 //
 
 import UIKit
-import CoreData
+import WebKit
+import OSLog
 
 @main
 class AppDelegate: UIResponder, UIApplicationDelegate {
 
-
-
     func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
-        // Override point for customization after application launch.
+        swizzleWKWebView()
+        
         return true
     }
 
@@ -31,6 +31,23 @@ class AppDelegate: UIResponder, UIApplicationDelegate {
         // If any sessions were discarded while the application was not running, this will be called shortly after application:didFinishLaunchingWithOptions.
         // Use this method to release any resources that were specific to the discarded scenes, as they will not return.
     }
+    
+    private func swizzleWKWebView() {
+        let selector = Selector(("_updateScrollViewBackground"))
+        var originalIMP: IMP?
+        let imp = imp_implementationWithBlock({ (self: WKWebView) in
+            if let originalIMP = originalIMP {
+                let original = unsafeBitCast(originalIMP, to: (@convention(c) (WKWebView, Selector) -> Void).self)
+                original(self, selector)
+            } else {
+                os_log(.error, "Missing originalIMP for -[WKWebView _updateScrollViewBackground], did WebKit change?")
+            }
+            
+            self.scrollView.indicatorStyle = .default
+            
+        } as (@convention(block) (WKWebView) -> Void))
+        originalIMP = class_replaceMethod(WKWebView.self, selector, imp, "v@:")
+    }
 
 }