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WKWebView: Fix Blank Screen and Prevent Memory Leaks #16

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WKWebView: Fix Blank Screen and Prevent Memory Leaks #16

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136 changes: 128 additions & 8 deletions Sources/MarkdownWebView/MarkdownWebView.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -32,9 +32,9 @@ import WebKit
public func makeCoordinator() -> Coordinator { .init(parent: self) }

#if os(macOS)
public func makeNSView(context: Context) -> CustomWebView { context.coordinator.platformView }
public func makeNSView(context: Context) -> UIView { context.coordinator.containerView }
#elseif os(iOS)
public func makeUIView(context: Context) -> CustomWebView { context.coordinator.platformView }
public func makeUIView(context: Context) -> UIView { context.coordinator.containerView }
#endif

func updatePlatformView(_ platformView: CustomWebView, context _: Context) {
Expand All @@ -43,9 +43,9 @@ import WebKit
}

#if os(macOS)
public func updateNSView(_ nsView: CustomWebView, context: Context) { updatePlatformView(nsView, context: context) }
public func updateNSView(_ nsView: UIView, context: Context) { updatePlatformView(context.coordinator.platformView, context: context) }
#elseif os(iOS)
public func updateUIView(_ uiView: CustomWebView, context: Context) { updatePlatformView(uiView, context: context) }
public func updateUIView(_ uiView: UIView, context: Context) { updatePlatformView(context.coordinator.platformView, context: context) }
#endif

public func onLinkActivation(_ linkActivationHandler: @escaping (URL) -> Void) -> Self {
Expand All @@ -56,15 +56,86 @@ import WebKit
.init(markdownContent, customStylesheet: customStylesheet, linkActivationHandler: linkActivationHandler, renderedContentHandler: renderedContentHandler)
}

public class Coordinator: NSObject, WKNavigationDelegate, WKScriptMessageHandler {
let parent: MarkdownWebView
let platformView: CustomWebView
final class ContainerView: UIView {
weak var webView: CustomWebView?

override var intrinsicContentSize: CGSize {
// delegate intrinsic size to the web view
return webView?.intrinsicContentSize ?? .zero
}
}

public class Coordinator: NSObject, WKNavigationDelegate, WKScriptMessageHandler {
let containerView = ContainerView()

private let parent: MarkdownWebView
var platformView: CustomWebView!

deinit {
removeScriptMessageHandlers()
deinitWillEnterForegroundNotification()
}

init(parent: MarkdownWebView) {
self.parent = parent
platformView = .init()

super.init()

self.initPlatformView()

self.initWillEnterForegroundNotification()
}

private func deinitWillEnterForegroundNotification() {
NotificationCenter.default.removeObserver(self, name: UIScene.willEnterForegroundNotification, object: nil)
}

private func initWillEnterForegroundNotification() {
NotificationCenter.default.addObserver(
self,
selector: #selector(willEnterForeground),
name: UIScene.willEnterForegroundNotification,
object: nil
)
}

@objc func willEnterForeground(_ notification: Notification) {
performBlankCheck()
}

private func performBlankCheck() {
// Avoid checking while page is still loading to reduce false positives
guard let webView = platformView, !webView.isLoading else { return }

// Quick JS returning body text length (fast)
webView.evaluateJavaScript("document && document.body ? document.body.innerText.length : 0") { [weak self] result, error in
guard let self else { return }
if let error = error {
// JS errored — print debug (page might be blank / bad state)
//print("⚠️ MarkdownWebView blank-check JS error: \(error.localizedDescription)")
recreatePlatformViewAsync()
return
}

if let len = result as? Int {
if len == 0 {
//print("⚠️ MarkdownWebView appears blank (body text length == 0).")
recreatePlatformViewAsync()
} else {
// optional: for debug you can print length
//print("✅ MarkdownWebView content length: \(len)")
}
} else {
// unexpected type, print for debugging
//print("⚠️ MarkdownWebView blank-check unexpected result: \(String(describing: result))")
recreatePlatformViewAsync()
}
}
}

private func initPlatformView() {
platformView = .init()

platformView.navigationDelegate = self

#if DEBUG && os(iOS)
Expand Down Expand Up @@ -114,6 +185,52 @@ import WebKit
.replacingOccurrences(of: "PLACEHOLDER_SCRIPT", with: script)
.replacingOccurrences(of: "PLACEHOLDER_STYLESHEET", with: self.parent.customStylesheet ?? defaultStylesheet)
platformView.loadHTMLString(htmlString, baseURL: nil)

attach(platformView, to: containerView)
}

private func recreatePlatformViewAsync() {
DispatchQueue.main.async { [weak self] in
guard let self else { return }
guard let platformView else { return }

removeScriptMessageHandlers()

detach(platformView)

initPlatformView()
}
}

private func removeScriptMessageHandlers() {
platformView.configuration.userContentController.removeScriptMessageHandler(
forName: "sizeChangeHandler")
platformView.configuration.userContentController.removeScriptMessageHandler(
forName: "renderedContentHandler")
platformView.configuration.userContentController.removeScriptMessageHandler(
forName: "copyToPasteboard")
}

private func attach(_ webView: CustomWebView, to container: ContainerView) {
webView.translatesAutoresizingMaskIntoConstraints = false
container.addSubview(webView)
NSLayoutConstraint.activate([
webView.leadingAnchor.constraint(equalTo: container.leadingAnchor),
webView.trailingAnchor.constraint(equalTo: container.trailingAnchor),
webView.topAnchor.constraint(equalTo: container.topAnchor),
webView.bottomAnchor.constraint(equalTo: container.bottomAnchor)
])

container.webView = webView
}

private func detach(_ webView: CustomWebView) {
webView.removeFromSuperview()
}

public func webViewWebContentProcessDidTerminate(_ webView: WKWebView) {
//print("⚠️ Process terminated!")
recreatePlatformViewAsync()
}

/// Update the content on first finishing loading.
Expand Down Expand Up @@ -151,6 +268,9 @@ import WebKit
else { return }
platformView.contentHeight = contentHeight
platformView.invalidateIntrinsicContentSize()

containerView.invalidateIntrinsicContentSize()

case "renderedContentHandler":
guard let renderedContentHandler = parent.renderedContentHandler,
let renderedContentBase64Encoded = message.body as? String,
Expand Down