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LibWeb: Only allocate EventTarget listener/handler storage on demand

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This shaves 40 bytes off of all EventTargets that don't actually get
listeners or handlers attached (which is most of them).
This commit is contained in:
Andreas Kling 2023-11-18 11:15:08 +01:00
parent a71eaefdf6
commit c1fd55ce94
2 changed files with 54 additions and 27 deletions
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68
Userland/Libraries/LibWeb/DOM/EventTarget.cpp
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@ -66,17 +66,21 @@ void EventTarget::visit_edges(Cell::Visitor& visitor)
{
Base::visit_edges(visitor);
for (auto& event_listener : m_event_listener_list)
visitor.visit(event_listener);
if (auto const* data = m_data.ptr()) {
for (auto& event_listener : data->event_listener_list)
visitor.visit(event_listener);
for (auto& it : m_event_handler_map)
visitor.visit(it.value);
for (auto& it : data->event_handler_map)
visitor.visit(it.value);
}
}
Vector<JS::Handle<DOMEventListener>> EventTarget::event_listener_list()
{
Vector<JS::Handle<DOMEventListener>> list;
for (auto& listener : m_event_listener_list)
if (!m_data)
return list;
for (auto& listener : m_data->event_listener_list)
list.append(*listener);
return list;
}
@ -170,6 +174,8 @@ void EventTarget::add_an_event_listener(DOMEventListener& listener)
// and listener’s type matches the type attribute value of any of the service worker events, then report a warning to the console
// that this might not give the expected results. [SERVICE-WORKERS]
auto& event_listener_list = ensure_data().event_listener_list;
// 2. If listener’s signal is not null and is aborted, then return.
if (listener.signal && listener.signal->aborted())
return;
@ -180,13 +186,13 @@ void EventTarget::add_an_event_listener(DOMEventListener& listener)
// 4. If eventTarget’s event listener list does not contain an event listener whose type is listener’s type, callback is listener’s callback,
// and capture is listener’s capture, then append listener to eventTarget’s event listener list.
auto it = m_event_listener_list.find_if([&](auto& entry) {
auto it = event_listener_list.find_if([&](auto& entry) {
return entry->type == listener.type
&& entry->callback->callback().callback == listener.callback->callback().callback
&& entry->capture == listener.capture;
});
if (it == m_event_listener_list.end())
m_event_listener_list.append(listener);
if (it == event_listener_list.end())
event_listener_list.append(listener);
// 5. If listener’s signal is not null, then add the following abort steps to it:
if (listener.signal) {
@ -201,6 +207,8 @@ void EventTarget::add_an_event_listener(DOMEventListener& listener)
// https://dom.spec.whatwg.org/#dom-eventtarget-removeeventlistener
void EventTarget::remove_event_listener(FlyString const& type, IDLEventListener* callback, Variant<EventListenerOptions, bool> const& options)
{
auto& event_listener_list = ensure_data().event_listener_list;
// 1. Let capture be the result of flattening options.
bool capture = flatten_event_listener_options(options);
@ -213,12 +221,12 @@ void EventTarget::remove_event_listener(FlyString const& type, IDLEventListener*
return false;
return entry.callback->callback().callback == callback->callback().callback;
};
auto it = m_event_listener_list.find_if([&](auto& entry) {
auto it = event_listener_list.find_if([&](auto& entry) {
return entry->type == type
&& callbacks_match(*entry)
&& entry->capture == capture;
});
if (it != m_event_listener_list.end())
if (it != event_listener_list.end())
remove_an_event_listener(**it);
}
@ -235,12 +243,15 @@ void EventTarget::remove_an_event_listener(DOMEventListener& listener)
// 2. Set listener’s removed to true and remove listener from eventTarget’s event listener list.
listener.removed = true;
m_event_listener_list.remove_first_matching([&](auto& entry) { return entry.ptr() == &listener; });
VERIFY(m_data);
m_data->event_listener_list.remove_first_matching([&](auto& entry) { return entry.ptr() == &listener; });
}
void EventTarget::remove_from_event_listener_list(DOMEventListener& listener)
{
m_event_listener_list.remove_first_matching([&](auto& entry) { return entry.ptr() == &listener; });
if (!m_data)
return;
m_data->event_listener_list.remove_first_matching([&](auto& entry) { return entry.ptr() == &listener; });
}
// https://dom.spec.whatwg.org/#dom-eventtarget-dispatchevent
@ -337,16 +348,17 @@ WebIDL::CallbackType* EventTarget::event_handler_attribute(FlyString const& name
WebIDL::CallbackType* EventTarget::get_current_value_of_event_handler(FlyString const& name)
{
// 1. Let handlerMap be eventTarget's event handler map. (NOTE: Not necessary)
auto& handler_map = ensure_data().event_handler_map;
// 2. Let eventHandler be handlerMap[name].
auto event_handler_iterator = m_event_handler_map.find(name);
auto event_handler_iterator = handler_map.find(name);
// Optimization: The spec creates all the event handlers exposed on an object up front and has the initial value of the handler set to null.
// If the event handler hasn't been set, null would be returned in step 4.
// However, this would be very allocation heavy. For example, each DOM::Element includes GlobalEventHandlers, which defines 60+(!) event handler attributes.
// Plus, the vast majority of these allocations would be likely wasted, as I imagine web content will only use a handful of these attributes on certain elements, if any at all.
// Thus, we treat the event handler not being in the event handler map as being equivalent to an event handler with an initial null value.
if (event_handler_iterator == m_event_handler_map.end())
if (event_handler_iterator == handler_map.end())
return nullptr;
auto& event_handler = event_handler_iterator->value;
@ -418,7 +430,7 @@ WebIDL::CallbackType* EventTarget::get_current_value_of_event_handler(FlyString
if (parser.has_errors()) {
// 1. Set eventHandler's value to null.
// Note: This does not deactivate the event handler, which additionally removes the event handler's listener (if present).
m_event_handler_map.remove(event_handler_iterator);
handler_map.remove(event_handler_iterator);
// FIXME: 2. Report the error for the appropriate script and with the appropriate position (line number and column number) given by location, using settings object's global object.
// If the error is still not handled after this, then the error may be reported to a developer console.
@ -510,7 +522,7 @@ void EventTarget::set_event_handler_attribute(FlyString const& name, WebIDL::Cal
// 4. Otherwise:
// 1. Let handlerMap be eventTarget's event handler map.
auto& handler_map = event_target->m_event_handler_map;
auto& handler_map = event_target->ensure_data().event_handler_map;
// 2. Let eventHandler be handlerMap[name].
auto event_handler_iterator = handler_map.find(name);
@ -592,13 +604,14 @@ void EventTarget::activate_event_handler(FlyString const& name, HTML::EventHandl
void EventTarget::deactivate_event_handler(FlyString const& name)
{
// 1. Let handlerMap be eventTarget's event handler map. (NOTE: Not necessary)
// 1. Let handlerMap be eventTarget's event handler map.
auto& handler_map = ensure_data().event_handler_map;
// 2. Let eventHandler be handlerMap[name].
auto event_handler_iterator = m_event_handler_map.find(name);
auto event_handler_iterator = handler_map.find(name);
// NOTE: See the optimization comment in get_current_value_of_event_handler about why this is done.
if (event_handler_iterator == m_event_handler_map.end())
if (event_handler_iterator == handler_map.end())
return;
auto& event_handler = event_handler_iterator->value;
@ -616,7 +629,7 @@ void EventTarget::deactivate_event_handler(FlyString const& name)
// 3. Set eventHandler's value to null.
// NOTE: This is done out of order since our equivalent of setting value to null is removing the event handler from the map.
// Given that event_handler is a reference to an entry, this would invalidate event_handler if we did it in order.
m_event_handler_map.remove(event_handler_iterator);
handler_map.remove(event_handler_iterator);
}
// https://html.spec.whatwg.org/multipage/webappapis.html#the-event-handler-processing-algorithm
@ -721,7 +734,7 @@ void EventTarget::element_event_handler_attribute_changed(FlyString const& local
// FIXME: 1. If the Should element's inline behavior be blocked by Content Security Policy? algorithm returns "Blocked" when executed upon element, "script attribute", and value, then return. [CSP]
// 2. Let handlerMap be eventTarget's event handler map.
auto& handler_map = event_target->m_event_handler_map;
auto& handler_map = event_target->ensure_data().event_handler_map;
// 3. Let eventHandler be handlerMap[localName].
auto event_handler_iterator = handler_map.find(local_name);
@ -804,7 +817,9 @@ bool EventTarget::dispatch_event(Event& event)
bool EventTarget::has_event_listener(FlyString const& type) const
{
for (auto& listener : m_event_listener_list) {
if (!m_data)
return false;
for (auto& listener : m_data->event_listener_list) {
if (listener->type == type)
return true;
}
@ -813,7 +828,7 @@ bool EventTarget::has_event_listener(FlyString const& type) const
bool EventTarget::has_event_listeners() const
{
return !m_event_listener_list.is_empty();
return m_data && !m_data->event_listener_list.is_empty();
}
bool EventTarget::has_activation_behavior() const
@ -825,4 +840,11 @@ void EventTarget::activation_behavior(Event const&)
{
}
auto EventTarget::ensure_data() -> Data&
{
if (!m_data)
m_data = make<Data>();
return *m_data;
}
}