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- // Copyright (c) 2012 The Chromium Authors. All rights reserved.
- // Use of this source code is governed by a BSD-style license that can be
- // found in the LICENSE file.
- #ifndef UI_EVENTS_EVENT_DISPATCHER_H_
- #define UI_EVENTS_EVENT_DISPATCHER_H_
- #include "base/auto_reset.h"
- #include "base/memory/raw_ptr.h"
- #include "ui/events/event.h"
- #include "ui/events/event_constants.h"
- #include "ui/events/event_handler.h"
- #include "ui/events/events_export.h"
- namespace ui {
- class EventDispatcher;
- class EventTarget;
- struct EventDispatchDetails {
- bool dispatcher_destroyed = false;
- bool target_destroyed = false;
- // Set to true if an EventRewriter discards the event.
- bool event_discarded = false;
- };
- class EVENTS_EXPORT EventDispatcherDelegate {
- public:
- EventDispatcherDelegate();
- EventDispatcherDelegate(const EventDispatcherDelegate&) = delete;
- EventDispatcherDelegate& operator=(const EventDispatcherDelegate&) = delete;
- virtual ~EventDispatcherDelegate();
- // Returns whether an event can still be dispatched to a target. (e.g. during
- // event dispatch, one of the handlers may have destroyed the target, in which
- // case the event can no longer be dispatched to the target).
- virtual bool CanDispatchToTarget(EventTarget* target) = 0;
- // Returns the event being dispatched (or NULL if no event is being
- // dispatched).
- Event* current_event();
- // Dispatches |event| to |target|. This calls |PreDispatchEvent()| before
- // dispatching the event, and |PostDispatchEvent()| after the event has been
- // dispatched.
- [[nodiscard]] EventDispatchDetails DispatchEvent(EventTarget* target,
- Event* event);
- protected:
- // This is called once a target has been determined for an event, right before
- // the event is dispatched to the target. This function may modify |event| to
- // prepare it for dispatch (e.g. update event flags, location etc.).
- [[nodiscard]] virtual EventDispatchDetails PreDispatchEvent(
- EventTarget* target,
- Event* event);
- // This is called right after the event dispatch is completed.
- // |target| is NULL if the target was deleted during dispatch.
- [[nodiscard]] virtual EventDispatchDetails PostDispatchEvent(
- EventTarget* target,
- const Event& event);
- private:
- // Dispatches the event to the target.
- [[nodiscard]] EventDispatchDetails DispatchEventToTarget(EventTarget* target,
- Event* event);
- raw_ptr<EventDispatcher> dispatcher_;
- };
- // Dispatches events to appropriate targets.
- class EVENTS_EXPORT EventDispatcher {
- public:
- explicit EventDispatcher(EventDispatcherDelegate* delegate);
- EventDispatcher(const EventDispatcher&) = delete;
- EventDispatcher& operator=(const EventDispatcher&) = delete;
- virtual ~EventDispatcher();
- void ProcessEvent(EventTarget* target, Event* event);
- const Event* current_event() const { return current_event_; }
- Event* current_event() { return current_event_; }
- bool delegate_destroyed() const { return !delegate_; }
- void OnHandlerDestroyed(EventHandler* handler);
- void OnDispatcherDelegateDestroyed();
- private:
- void DispatchEventToEventHandlers(EventHandlerList* list, Event* event);
- // Dispatches an event, and makes sure it sets ER_CONSUMED on the
- // event-handling result if the dispatcher itself has been destroyed during
- // dispatching the event to the event handler.
- void DispatchEvent(EventHandler* handler, Event* event);
- raw_ptr<EventDispatcherDelegate> delegate_;
- Event* current_event_ = nullptr;
- EventHandlerList handler_list_;
- };
- } // namespace ui
- #endif // UI_EVENTS_EVENT_DISPATCHER_H_
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