LibWeb: Add a NavigationObserver to be notified of navigable updates

This contains a hook to be notified when a navigable navigation is
complete, to be used by WebDriver.

(cherry picked from commit 74ef9dc3936d678fdf811bb3c1b39a6ffba2b106)

Userland/Libraries/LibWeb/CMakeLists.txt

@@ -410,6 +410,7 @@ set(SOURCES
     HTML/NavigationDestination.cpp
     HTML/NavigationCurrentEntryChangeEvent.cpp
     HTML/NavigationHistoryEntry.cpp
+    HTML/NavigationObserver.cpp
     HTML/NavigationParams.cpp
     HTML/NavigationTransition.cpp
     HTML/Navigator.cpp

Userland/Libraries/LibWeb/Forward.h

@@ -490,6 +490,7 @@ class Navigation;
 class NavigationCurrentEntryChangeEvent;
 class NavigationDestination;
 class NavigationHistoryEntry;
+class NavigationObserver;
 class NavigationTransition;
 class Navigator;
 class PageTransitionEvent;

Userland/Libraries/LibWeb/HTML/Navigable.cpp

@@ -21,6 +21,7 @@
 #include <LibWeb/HTML/HistoryHandlingBehavior.h>
 #include <LibWeb/HTML/Navigable.h>
 #include <LibWeb/HTML/Navigation.h>
+#include <LibWeb/HTML/NavigationObserver.h>
 #include <LibWeb/HTML/NavigationParams.h>
 #include <LibWeb/HTML/POSTResource.h>
 #include <LibWeb/HTML/Parser/HTMLParser.h>
@@ -124,6 +125,7 @@ void Navigable::visit_edges(Cell::Visitor& visitor)
     visitor.visit(m_current_session_history_entry);
     visitor.visit(m_active_session_history_entry);
     visitor.visit(m_container);
+    visitor.visit(m_navigation_observers);
     m_event_handler.visit_edges(visitor);
 }
 
@@ -213,6 +215,13 @@ void Navigable::activate_history_entry(JS::GCPtr<SessionHistoryEntry> entry)
 
     // 5. Make active newDocument.
     new_document->make_active();
+
+    if (m_ongoing_navigation.has<Empty>()) {
+        for (auto navigation_observer : m_navigation_observers) {
+            if (navigation_observer->navigation_complete())
+                navigation_observer->navigation_complete()->function()();
+        }
+    }
 }
 
 // https://html.spec.whatwg.org/multipage/document-sequences.html#nav-document
@@ -2228,4 +2237,16 @@ void Navigable::paste(String const& text)
     m_event_handler.handle_paste(text);
 }
 
+void Navigable::register_navigation_observer(Badge<NavigationObserver>, NavigationObserver& navigation_observer)
+{
+    auto result = m_navigation_observers.set(navigation_observer);
+    VERIFY(result == AK::HashSetResult::InsertedNewEntry);
+}
+
+void Navigable::unregister_navigation_observer(Badge<NavigationObserver>, NavigationObserver& navigation_observer)
+{
+    bool was_removed = m_navigation_observers.remove(navigation_observer);
+    VERIFY(was_removed);
+}
+
 }

Userland/Libraries/LibWeb/HTML/Navigable.h

@@ -57,6 +57,9 @@ public:
 
     ErrorOr<void> initialize_navigable(JS::NonnullGCPtr<DocumentState> document_state, JS::GCPtr<Navigable> parent);
 
+    void register_navigation_observer(Badge<NavigationObserver>, NavigationObserver&);
+    void unregister_navigation_observer(Badge<NavigationObserver>, NavigationObserver&);
+
     Vector<JS::Handle<Navigable>> child_navigables() const;
 
     bool is_traversable() const;
@@ -239,6 +242,8 @@ private:
 
     JS::NonnullGCPtr<Page> m_page;
 
+    HashTable<JS::NonnullGCPtr<NavigationObserver>> m_navigation_observers;
+
     bool m_has_been_destroyed { false };
 
     CSSPixelSize m_size;

Userland/Libraries/LibWeb/HTML/NavigationObserver.cpp

@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2024, Tim Flynn <trflynn89@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibJS/Runtime/Realm.h>
+#include <LibWeb/HTML/Navigable.h>
+#include <LibWeb/HTML/NavigationObserver.h>
+
+namespace Web::HTML {
+
+JS_DEFINE_ALLOCATOR(NavigationObserver);
+
+NavigationObserver::NavigationObserver(JS::Realm& realm, Navigable& navigable)
+    : Bindings::PlatformObject(realm)
+    , m_navigable(navigable)
+{
+    m_navigable->register_navigation_observer({}, *this);
+}
+
+void NavigationObserver::visit_edges(Cell::Visitor& visitor)
+{
+    Base::visit_edges(visitor);
+    visitor.visit(m_navigable);
+    visitor.visit(m_navigation_complete);
+}
+
+void NavigationObserver::finalize()
+{
+    Base::finalize();
+    m_navigable->unregister_navigation_observer({}, *this);
+}
+
+void NavigationObserver::set_navigation_complete(Function<void()> callback)
+{
+    if (callback)
+        m_navigation_complete = JS::create_heap_function(vm().heap(), move(callback));
+    else
+        m_navigation_complete = nullptr;
+}
+
+}

Userland/Libraries/LibWeb/HTML/NavigationObserver.h

@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) 2024, Tim Flynn <trflynn89@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibJS/Heap/GCPtr.h>
+#include <LibJS/Heap/HeapFunction.h>
+#include <LibWeb/Bindings/PlatformObject.h>
+#include <LibWeb/Forward.h>
+
+namespace Web::HTML {
+
+class NavigationObserver final : public Bindings::PlatformObject {
+    WEB_PLATFORM_OBJECT(NavigationObserver, Bindings::PlatformObject);
+    JS_DECLARE_ALLOCATOR(NavigationObserver);
+
+public:
+    [[nodiscard]] JS::GCPtr<JS::HeapFunction<void()>> navigation_complete() const { return m_navigation_complete; }
+    void set_navigation_complete(Function<void()>);
+
+private:
+    NavigationObserver(JS::Realm&, Navigable&);
+
+    virtual void visit_edges(Cell::Visitor&) override;
+    virtual void finalize() override;
+
+    JS::NonnullGCPtr<Navigable> m_navigable;
+    JS::GCPtr<JS::HeapFunction<void()>> m_navigation_complete;
+};
+
+}