LibWeb: Implement PerformanceObserver

Userland/Libraries/LibWeb/PerformanceTimeline/PerformanceObserver.h

@@ -0,0 +1,77 @@
+/*
+ * Copyright (c) 2023, Luke Wilde <lukew@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibWeb/Bindings/PlatformObject.h>
+#include <LibWeb/HTML/WindowOrWorkerGlobalScope.h>
+
+namespace Web::PerformanceTimeline {
+
+// https://w3c.github.io/performance-timeline/#dom-performanceobserverinit
+struct PerformanceObserverInit {
+    Optional<Vector<String>> entry_types;
+    Optional<String> type;
+    Optional<bool> buffered;
+};
+
+// https://w3c.github.io/performance-timeline/#dom-performanceobserver
+class PerformanceObserver final : public Bindings::PlatformObject {
+    WEB_PLATFORM_OBJECT(PerformanceObserver, Bindings::PlatformObject);
+
+public:
+    enum class ObserverType {
+        Undefined,
+        Single,
+        Multiple,
+    };
+
+    static WebIDL::ExceptionOr<JS::NonnullGCPtr<PerformanceObserver>> construct_impl(JS::Realm&, JS::GCPtr<WebIDL::CallbackType>);
+    virtual ~PerformanceObserver() override;
+
+    WebIDL::ExceptionOr<void> observe(PerformanceObserverInit& options);
+    void disconnect();
+    Vector<JS::Handle<PerformanceTimeline::PerformanceEntry>> take_records();
+
+    bool requires_dropped_entries() const { return m_requires_dropped_entries; }
+    void unset_requires_dropped_entries(Badge<HTML::WindowOrWorkerGlobalScopeMixin>);
+
+    Vector<PerformanceObserverInit> const& options_list() const { return m_options_list; }
+
+    WebIDL::CallbackType& callback() { return *m_callback; }
+
+    void append_to_observer_buffer(Badge<HTML::WindowOrWorkerGlobalScopeMixin>, JS::NonnullGCPtr<PerformanceTimeline::PerformanceEntry>);
+
+private:
+    PerformanceObserver(JS::Realm&, JS::GCPtr<WebIDL::CallbackType>);
+
+    virtual void initialize(JS::Realm&) override;
+    virtual void visit_edges(Cell::Visitor&) override;
+
+    // https://w3c.github.io/performance-timeline/#dfn-observer-callback
+    // A PerformanceObserverCallback observer callback set on creation.
+    JS::GCPtr<WebIDL::CallbackType> m_callback;
+
+    // https://w3c.github.io/performance-timeline/#dfn-observer-buffer
+    // A PerformanceEntryList object called the observer buffer that is initially empty.
+    Vector<JS::NonnullGCPtr<PerformanceTimeline::PerformanceEntry>> m_observer_buffer;
+
+    // https://w3c.github.io/performance-timeline/#dfn-observer-type
+    // A DOMString observer type which is initially "undefined".
+    ObserverType m_observer_type { ObserverType::Undefined };
+
+    // https://w3c.github.io/performance-timeline/#dfn-requires-dropped-entries
+    // A boolean requires dropped entries which is initially set to false.
+    bool m_requires_dropped_entries { false };
+
+    // https://w3c.github.io/performance-timeline/#dfn-options-list
+    // A registered performance observer is a struct consisting of an observer member (a PerformanceObserver object)
+    // and an options list member (a list of PerformanceObserverInit dictionaries).
+    // NOTE: This doesn't use a separate struct as methods such as disconnect() assume it can access an options list from `this`: a PerformanceObserver.
+    Vector<PerformanceObserverInit> m_options_list;
+};
+
+}