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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_TARGET_H_
- #define UI_EVENTS_EVENT_TARGET_H_
- #include <memory>
- #include <vector>
- #include "base/memory/raw_ptr.h"
- #include "ui/events/event_handler.h"
- #include "ui/events/events_export.h"
- #include "ui/gfx/geometry/point.h"
- #include "ui/gfx/geometry/point_f.h"
- namespace ui {
- class EventDispatcher;
- class EventTargeter;
- class EventTargetIterator;
- class LocatedEvent;
- class EVENTS_EXPORT EventTarget {
- public:
- class DispatcherApi {
- public:
- explicit DispatcherApi(EventTarget* target) : target_(target) {}
- DispatcherApi(const DispatcherApi&) = delete;
- DispatcherApi& operator=(const DispatcherApi&) = delete;
- private:
- DispatcherApi();
- raw_ptr<EventTarget> target_;
- };
- EventTarget();
- EventTarget(const EventTarget&) = delete;
- EventTarget& operator=(const EventTarget&) = delete;
- virtual ~EventTarget();
- virtual bool CanAcceptEvent(const Event& event) = 0;
- // Returns the parent EventTarget in the event-target tree.
- virtual EventTarget* GetParentTarget() = 0;
- // Returns an iterator an EventTargeter can use to iterate over the list of
- // child EventTargets.
- virtual std::unique_ptr<EventTargetIterator> GetChildIterator() const = 0;
- // Returns the EventTargeter that should be used to find the target for an
- // event in the subtree rooted at this EventTarget.
- virtual EventTargeter* GetEventTargeter() = 0;
- // Updates the states in |event| (e.g. location) to be suitable for |target|,
- // so that |event| can be dispatched to |target|.
- virtual void ConvertEventToTarget(const EventTarget* target,
- LocatedEvent* event) const;
- // Get |event|'s screen location, using the EventTarget's screen location.
- virtual gfx::PointF GetScreenLocationF(const LocatedEvent& event) const;
- gfx::Point GetScreenLocation(const LocatedEvent& event) const;
- // Priority levels for PreTargetHandlers.
- enum class Priority {
- // The Accessibility level is the highest, and gets events before
- // other priority levels. This allows accessibility features to
- // modify events directly from the user.
- kAccessibility,
- // System priority EventHandlers get events before default level, and
- // should be used for drag and drop, menus, etc.
- kSystem,
- // The default level should be used by most EventHandlers.
- kDefault,
- };
- // Adds a handler to receive events before the target. The handler must be
- // explicitly removed from the target before the handler is destroyed. The
- // EventTarget does not take ownership of the handler.
- void AddPreTargetHandler(EventHandler* handler);
- void AddPreTargetHandler(EventHandler* handler, Priority priority);
- void RemovePreTargetHandler(EventHandler* handler);
- // Adds a handler to receive events after the target. The handler must be
- // explicitly removed from the target before the handler is destroyed. The
- // EventTarget does not take ownership of the handler.
- void AddPostTargetHandler(EventHandler* handler);
- void RemovePostTargetHandler(EventHandler* handler);
- // Returns true if the event pre target list is empty.
- bool IsPreTargetListEmpty() const;
- // Sets |target_handler| as |target_handler_| and returns the old handler.
- EventHandler* SetTargetHandler(EventHandler* target_handler);
- bool HasTargetHandler() const { return target_handler_ != nullptr; }
- protected:
- EventHandler* target_handler() { return target_handler_; }
- private:
- friend class EventDispatcher;
- friend class EventTargetTestApi;
- // A handler with a priority.
- struct PrioritizedHandler {
- EventHandler* handler = nullptr;
- Priority priority = Priority::kDefault;
- bool operator<(const PrioritizedHandler& ph) const {
- return priority < ph.priority;
- }
- };
- using EventHandlerPriorityList = std::vector<PrioritizedHandler>;
- // Returns the list of handlers that should receive the event before the
- // target. The handlers from the outermost target are first in the list, and
- // the handlers on |this| are the last in the list.
- void GetPreTargetHandlers(EventHandlerList* list);
- // Returns the list of handlers that should receive the event after the
- // target. The handlers from the outermost target are last in the list, and
- // the handlers on |this| are the first in the list.
- void GetPostTargetHandlers(EventHandlerList* list);
- EventHandlerPriorityList pre_target_list_;
- EventHandlerList post_target_list_;
- // TODO(crbug.com/1298696): Breaks content_unittests.
- raw_ptr<EventHandler, DegradeToNoOpWhenMTE> target_handler_ = nullptr;
- };
- } // namespace ui
- #endif // UI_EVENTS_EVENT_TARGET_H_
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