Trait WebViewDelegate 

pub trait WebViewDelegate: Send + Sync {
    // Required methods
    fn on_navigation_event(&self, event: NavigationEvent);
    fn handle_post_message(&self, message: IncomingWebMessage);
    fn log(&self, level: LogLevel, message: &str);

    // Provided methods
    fn on_webview_state_change(&self, _change: WebViewStateChange) { ... }
    fn on_document_committed(
        &self,
        _native_view: NativeWebViewId,
        _generation: DocumentGeneration,
        _navigation_id: NavigationId,
    ) { ... }
    fn on_trusted_document_admitted(&self, _admission: TrustedDocumentAdmission) { ... }
    fn on_web_content_process_terminated(&self, _native_view: NativeWebViewId) { ... }
    fn on_document_restored(&self, _native_view: NativeWebViewId, _url: &str) { ... }
    fn handle_native_component_message(&self, _message_json: String) { ... }
}

WebView delegate: typed navigation lifecycle, observable state, page messaging, and logging for one WebView. Exactly one owner per WebView (an lxapp PageInstance or a browser tab delegate); read-only watchers use crate::events::normalizer::add_observer-registered observers.

Delivery contract (enforced by the event normalizer):

• events arrive by value, serially, synchronously on the submitting thread, flattened FIFO — a callback is never re-entered for the same WebView;
• callbacks may arrive on the WebView’s own UI thread; fire-and-forget commands (exec_js) are safe there, but result-awaiting APIs must not block the callback thread;
• every Started gets exactly one terminal event; success owns a non-empty final URL; cancellation is control flow, never a load error;
• state changes are snapshots, not lifecycle: Location alone is never evidence of a successful visit, and None clears title/favicon.

Fold navigation through crate::events::NavigationProgress and state through crate::events::ObservedWebViewState instead of hand-rolling attempt correlation:

fn on_navigation_event(&self, event: NavigationEvent) {
    let mut progress = self.progress.lock().unwrap();
    progress.apply(&event);
    if let NavigationEvent::Succeeded { id, final_url } = &event
        && progress.is_current(*id)
    {
        self.loaded(final_url);
    }
}

Required Methods

fn on_navigation_event(&self, event: NavigationEvent)

One correlated top-level navigation lifecycle event.

Required: after the typed-event migration every delegate must decide how it handles the lifecycle — a silent default would lose page loads.

fn handle_post_message(&self, message: IncomingWebMessage)

Handles a postMessage from the page View(WebView).

The context is assembled only by the platform adapter and must travel with the payload through any bridge admission decision.

fn log(&self, level: LogLevel, message: &str)

Receive log from WebView

Provided Methods

fn on_webview_state_change(&self, _change: WebViewStateChange)

One observable-state snapshot (location, title, favicon, back/forward availability), coalesced and generation-scoped by the normalizer.

fn on_document_committed( &self, _native_view: NativeWebViewId, _generation: DocumentGeneration, _navigation_id: NavigationId, )

A top-level document binding minted from reliable, non-stale commit evidence. It is never emitted for duplicate or ambiguous commits.

fn on_trusted_document_admitted(&self, _admission: TrustedDocumentAdmission)

A trusted native HTML load that reached a reliably committed document.

This is stricter than Self::on_document_committed: it is emitted only when the platform returned the exact native navigation key for a direct native load and the normalizer bound that key to this accepted navigation. The data and base URL used for the load are not authority.

fn on_web_content_process_terminated(&self, _native_view: NativeWebViewId)

The platform terminated this exact WebView’s content process. Only adapters with native evidence emit it; consumers must revoke any document authority before allowing a replacement to load.

fn on_document_restored(&self, _native_view: NativeWebViewId, _url: &str)

A backend proved that a previously committed document was restored without a fresh native start/commit chain (for example from BFCache). The adapter revokes its generation before invoking this hook.

fn handle_native_component_message(&self, _message_json: String)

Handles a native-component message posted by the page through the embedded-component channel (window.NativeComponentBridge), where the platform routes it in-process (currently Windows/WebView2). message_json is the raw component message (component.mount, component.update, …).

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors