LibWeb: Make event dispatching spec-compliant

Specification: https://dom.spec.whatwg.org/#concept-event-dispatch

This also introduces shadow roots due to it being a requirement of
the event dispatcher.

However, it does not introduce the full shadow DOM, that can be
left for future work.

This changes some event dispatches which require certain attributes
to be initialised to a value.

Libraries/LibWeb/DOM/Event.h

@@ -28,6 +28,7 @@
 
 #include <AK/FlyString.h>
 #include <LibWeb/Bindings/Wrappable.h>
+#include <LibWeb/DOM/EventTarget.h>
 
 namespace Web::DOM {
 
@@ -37,6 +38,28 @@ class Event
 public:
     using WrapperType = Bindings::EventWrapper;
 
+    enum Phase : u16 {
+        None = 0,
+        CapturingPhase = 1,
+        AtTarget = 2,
+        BubblingPhase = 3,
+    };
+
+    using TouchTargetList = Vector<RefPtr<EventTarget>>;
+
+    struct PathEntry {
+        RefPtr<EventTarget> invocation_target;
+        bool invocation_target_in_shadow_tree { false };
+        RefPtr<EventTarget> shadow_adjusted_target;
+        RefPtr<EventTarget> related_target;
+        TouchTargetList touch_target_list;
+        bool root_of_closed_tree { false };
+        bool slot_in_closed_tree { false };
+        size_t index;
+    };
+
+    using Path = Vector<PathEntry>;
+
     static NonnullRefPtr<Event> create(const FlyString& event_name)
     {
         return adopt(*new Event(event_name));
@@ -45,6 +68,86 @@ public:
     virtual ~Event() { }
 
     const FlyString& type() const { return m_type; }
+    void set_type(const StringView& type) { m_type = type; }
+
+    RefPtr<EventTarget> target() const { return m_target; }
+    void set_target(EventTarget* target) { m_target = target; }
+
+    // NOTE: This is intended for the JS bindings.
+    RefPtr<EventTarget> src_target() const { return target(); }
+
+    RefPtr<EventTarget> related_target() const { return m_related_target; }
+    void set_related_target(EventTarget* related_target) { m_related_target = related_target; }
+
+    bool should_stop_propagation() const { return m_stop_propagation; }
+    void set_stop_propagation(bool stop_propagation) { m_stop_propagation = stop_propagation; }
+
+    bool should_stop_immediate_propagation() const { return m_stop_immediate_propagation; }
+    void set_stop_immediate_propagation(bool stop_immediate_propagation) { m_stop_immediate_propagation = stop_immediate_propagation; }
+
+    bool cancelled() const { return m_cancelled; }
+    void set_cancelled(bool cancelled) { m_cancelled = cancelled; }
+
+    bool in_passive_listener() const { return m_in_passive_listener; }
+    void set_in_passive_listener(bool in_passive_listener) { m_in_passive_listener = in_passive_listener; }
+
+    bool composed() const { return m_composed; }
+    void set_composed(bool composed) { m_composed = composed; }
+
+    bool initialized() const { return m_initialized; }
+    void set_initialized(bool initialized) { m_initialized = initialized; }
+
+    bool dispatched() const { return m_dispatch; }
+    void set_dispatched(bool dispatched) { m_dispatch = dispatched; }
+
+    void prevent_default() { set_cancelled_flag(); }
+    bool default_prevented() const { return cancelled(); }
+
+    u16 event_phase() const { return m_phase; }
+    void set_phase(Phase phase) { m_phase = phase; }
+
+    RefPtr<EventTarget> current_target() const { return m_current_target; }
+    void set_current_target(EventTarget* current_target) { m_current_target = current_target; }
+
+    bool return_value() const { return !m_cancelled; }
+    void set_return_value(bool return_value)
+    {
+        if (!return_value)
+            set_cancelled_flag();
+    }
+
+    void append_to_path(EventTarget&, RefPtr<EventTarget>, RefPtr<EventTarget>, TouchTargetList&, bool);
+    Path& path() { return m_path; }
+    const Path& path() const { return m_path; }
+    void clear_path() { m_path.clear(); }
+
+    void set_touch_target_list(TouchTargetList& touch_target_list) { m_touch_target_list = touch_target_list; }
+    TouchTargetList& touch_target_list() { return m_touch_target_list; };
+    void clear_touch_target_list() { m_touch_target_list.clear(); }
+
+    bool bubbles() const { return m_bubbles; }
+    void set_bubbles(bool bubbles) { m_bubbles = bubbles; }
+
+    bool cancelable() const { return m_cancelable; }
+    void set_cancelable(bool cancelable) { m_cancelable = cancelable; }
+
+    bool is_trusted() const { return m_is_trusted; }
+    void set_is_trusted(bool is_trusted) { m_is_trusted = is_trusted; }
+
+    void stop_propagation() { m_stop_propagation = true; }
+
+    bool cancel_bubble() const { return m_stop_propagation; }
+    void set_cancel_bubble(bool cancel_bubble)
+    {
+        if (cancel_bubble)
+            m_stop_propagation = true;
+    }
+
+    void stop_immediate_propagation()
+    {
+        m_stop_propagation = true;
+        m_stop_immediate_propagation = true;
+    }
 
     virtual bool is_ui_event() const { return false; }
     virtual bool is_mouse_event() const { return false; }
@@ -52,11 +155,35 @@ public:
 protected:
     explicit Event(const FlyString& type)
         : m_type(type)
+        , m_initialized(true)
     {
     }
 
 private:
     FlyString m_type;
+    RefPtr<EventTarget> m_target;
+    RefPtr<EventTarget> m_related_target;
+    RefPtr<EventTarget> m_current_target;
+
+    Phase m_phase { None };
+
+    bool m_bubbles { false };
+    bool m_cancelable { false };
+
+    bool m_stop_propagation { false };
+    bool m_stop_immediate_propagation { false };
+    bool m_cancelled { false };
+    bool m_in_passive_listener { false };
+    bool m_composed { false };
+    bool m_initialized { false };
+    bool m_dispatch { false };
+
+    bool m_is_trusted { true };
+
+    Path m_path;
+    TouchTargetList m_touch_target_list;
+
+    void set_cancelled_flag();
 };
 
 }