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// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "ui/events/event_dispatcher.h"
#include "base/ranges/algorithm.h"
#include "ui/events/event_target.h"
#include "ui/events/event_targeter.h"
namespace ui {
namespace {
class ScopedDispatchHelper : public Event::DispatcherApi {
public:
explicit ScopedDispatchHelper(Event* event)
: Event::DispatcherApi(event) {
set_result(ui::ER_UNHANDLED);
}
ScopedDispatchHelper(const ScopedDispatchHelper&) = delete;
ScopedDispatchHelper& operator=(const ScopedDispatchHelper&) = delete;
virtual ~ScopedDispatchHelper() {
set_phase(EP_POSTDISPATCH);
}
};
} // namespace
EventDispatcherDelegate::EventDispatcherDelegate() : dispatcher_(nullptr) {}
EventDispatcherDelegate::~EventDispatcherDelegate() {
if (dispatcher_)
dispatcher_->OnDispatcherDelegateDestroyed();
}
Event* EventDispatcherDelegate::current_event() {
return dispatcher_ ? dispatcher_->current_event() : NULL;
}
EventDispatchDetails EventDispatcherDelegate::DispatchEvent(EventTarget* target,
Event* event) {
CHECK(target);
Event::DispatcherApi dispatch_helper(event);
dispatch_helper.set_phase(EP_PREDISPATCH);
dispatch_helper.set_result(ER_UNHANDLED);
EventDispatchDetails details = PreDispatchEvent(target, event);
if (!event->handled() &&
!details.dispatcher_destroyed &&
!details.target_destroyed) {
details = DispatchEventToTarget(target, event);
}
bool target_destroyed_during_dispatch = details.target_destroyed;
if (!details.dispatcher_destroyed) {
details = PostDispatchEvent(target_destroyed_during_dispatch ?
NULL : target, *event);
}
details.target_destroyed |= target_destroyed_during_dispatch;
return details;
}
EventDispatchDetails EventDispatcherDelegate::PreDispatchEvent(
EventTarget* target, Event* event) {
return EventDispatchDetails();
}
EventDispatchDetails EventDispatcherDelegate::PostDispatchEvent(
EventTarget* target, const Event& event) {
return EventDispatchDetails();
}
EventDispatchDetails EventDispatcherDelegate::DispatchEventToTarget(
EventTarget* target,
Event* event) {
EventDispatcher* old_dispatcher = dispatcher_;
EventDispatcher dispatcher(this);
dispatcher_ = &dispatcher;
dispatcher.ProcessEvent(target, event);
if (!dispatcher.delegate_destroyed())
dispatcher_ = old_dispatcher;
else if (old_dispatcher)
old_dispatcher->OnDispatcherDelegateDestroyed();
EventDispatchDetails details;
details.dispatcher_destroyed = dispatcher.delegate_destroyed();
details.target_destroyed =
(!details.dispatcher_destroyed && !CanDispatchToTarget(target));
return details;
}
////////////////////////////////////////////////////////////////////////////////
// EventDispatcher:
EventDispatcher::EventDispatcher(EventDispatcherDelegate* delegate)
: delegate_(delegate) {}
EventDispatcher::~EventDispatcher() {
// |handler_list_| must be empty, otherwise this has been added to an
// EventHandler that will callback to this when destroyed.
CHECK(handler_list_.empty());
}
void EventDispatcher::OnHandlerDestroyed(EventHandler* handler) {
handler_list_.erase(base::ranges::find(handler_list_, handler));
}
void EventDispatcher::ProcessEvent(EventTarget* target, Event* event) {
if (!target || !target->CanAcceptEvent(*event))
return;
ScopedDispatchHelper dispatch_helper(event);
dispatch_helper.set_target(target);
handler_list_.clear();
target->GetPreTargetHandlers(&handler_list_);
dispatch_helper.set_phase(EP_PRETARGET);
DispatchEventToEventHandlers(&handler_list_, event);
// All pre-target handler should have been removed.
CHECK(handler_list_.empty());
if (event->handled())
return;
// If the event hasn't been consumed, trigger the default handler. Note that
// even if the event has already been handled (i.e. return result has
// ER_HANDLED set), that means that the event should still be processed at
// this layer, however it should not be processed in the next layer of
// abstraction.
if (delegate_ && delegate_->CanDispatchToTarget(target) &&
target->target_handler()) {
dispatch_helper.set_phase(EP_TARGET);
DispatchEvent(target->target_handler(), event);
if (event->handled())
return;
}
if (!delegate_ || !delegate_->CanDispatchToTarget(target))
return;
target->GetPostTargetHandlers(&handler_list_);
dispatch_helper.set_phase(EP_POSTTARGET);
DispatchEventToEventHandlers(&handler_list_, event);
}
void EventDispatcher::OnDispatcherDelegateDestroyed() {
delegate_ = nullptr;
}
////////////////////////////////////////////////////////////////////////////////
// EventDispatcher, private:
void EventDispatcher::DispatchEventToEventHandlers(EventHandlerList* list,
Event* event) {
// Let each EventHandler know this is about to make use of it. This way, if
// during dispatch the EventHandler is destroyed it is removed from |list|
// (OnHandlerDestroyed() is called, which removes from |list|).
for (EventHandler* handler : *list)
handler->dispatchers_.push(this);
while (!list->empty()) {
EventHandler* handler = (*list->begin());
// |this| no longer needs to know if |handler| is destroyed.
CHECK(handler->dispatchers_.top() == this);
handler->dispatchers_.pop();
list->erase(list->begin());
// A null |delegate| means no more events should be dispatched.
if (delegate_ && !event->stopped_propagation())
DispatchEvent(handler, event);
}
}
void EventDispatcher::DispatchEvent(EventHandler* handler, Event* event) {
// If the target has been invalidated or deleted, don't dispatch the event.
if (!delegate_->CanDispatchToTarget(event->target())) {
if (event->cancelable())
event->StopPropagation();
return;
}
base::AutoReset<Event*> event_reset(¤t_event_, event);
handler->OnEvent(event);
if (!delegate_ && event->cancelable())
event->StopPropagation();
}
} // namespace ui
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