Ensure that the dom is fully loaded on *all* web views before being made available to process JavaScript. Issue #1756 & Issue #1808

iOS/Article/PreloadedWebView.swift

@@ -0,0 +1,81 @@
+//
+//  PreloadedWebView.swift
+//  NetNewsWire-iOS
+//
+//  Created by Maurice Parker on 2/25/20.
+//  Copyright © 2020 Ranchero Software. All rights reserved.
+//
+
+import Foundation
+import WebKit
+
+class PreloadedWebView: WKWebView {
+	
+	private struct MessageName {
+		static let domContentLoaded = "domContentLoaded"
+	}
+	
+	private var isReady: Bool = false
+	private var readyCompletion: ((PreloadedWebView) -> Void)?
+	
+	init(articleIconSchemeHandler: ArticleIconSchemeHandler) {
+		let preferences = WKPreferences()
+		preferences.javaScriptCanOpenWindowsAutomatically = false
+		preferences.javaScriptEnabled = true
+
+		let configuration = WKWebViewConfiguration()
+		configuration.preferences = preferences
+		configuration.setValue(true, forKey: "allowUniversalAccessFromFileURLs")
+		configuration.allowsInlineMediaPlayback = true
+		configuration.mediaTypesRequiringUserActionForPlayback = .video
+		configuration.setURLSchemeHandler(articleIconSchemeHandler, forURLScheme: ArticleRenderer.imageIconScheme)
+		
+		super.init(frame: .zero, configuration: configuration)
+	}
+	
+	required init?(coder: NSCoder) {
+		super.init(coder: coder)
+	}
+	
+	func preload() {
+		configuration.userContentController.add(WrapperScriptMessageHandler(self), name: MessageName.domContentLoaded)
+		loadFileURL(ArticleRenderer.page.url, allowingReadAccessTo: ArticleRenderer.page.baseURL)
+	}
+	
+	func ready(completion: @escaping (PreloadedWebView) -> Void) {
+		if isReady {
+			completeRequest(completion: completion)
+		} else {
+			readyCompletion = completion
+		}
+	}
+	
+}
+
+// MARK: WKScriptMessageHandler
+
+extension PreloadedWebView: WKScriptMessageHandler {
+
+	func userContentController(_ userContentController: WKUserContentController, didReceive message: WKScriptMessage) {
+		if message.name == MessageName.domContentLoaded {
+			isReady = true
+			if let completion = readyCompletion {
+				completeRequest(completion: completion)
+				readyCompletion = nil
+			}
+		}
+	}
+	
+}
+
+// MARK: Private
+
+private extension PreloadedWebView {
+	
+	func completeRequest(completion: @escaping (PreloadedWebView) -> Void) {
+		isReady = false
+		configuration.userContentController.removeScriptMessageHandler(forName: MessageName.domContentLoaded)
+		completion(self)
+	}
+	
+}