83 lines
2.4 KiB
C++
83 lines
2.4 KiB
C++
/**
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* Copyright (c) Facebook, Inc. and its affiliates.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*/
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#pragma once
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#include <memory>
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#include <mutex>
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#include <folly/dynamic.h>
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#include <fabric/events/EventDispatcher.h>
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#include <fabric/events/primitives.h>
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namespace facebook {
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namespace react {
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class EventEmitter;
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using SharedEventEmitter = std::shared_ptr<const EventEmitter>;
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/*
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* Base class for all particular typed event handlers.
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* Stores a pointer to `EventTarget` identifying a particular component and
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* a weak pointer to `EventDispatcher` which is responsible for delivering the event.
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*
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* Note: Retaining an `EventTarget` does *not* guarantee that actual event target
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* exists and/or valid in JavaScript realm. The `EventTarget` retains an `EventTargetWrapper`
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* which wraps JavaScript object in `unsafe-unretained` manner. Retaining
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* the `EventTarget` *does* indicate that we can use that to get an actual
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* JavaScript object from that in the future *ensuring safety beforehand somehow*;
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* JSI maintains `WeakObject` object as long as we retain the `EventTarget`.
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* All `EventTarget` instances must be deallocated before stopping JavaScript machine.
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*/
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class EventEmitter {
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/*
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* We have to repeat `Tag` type definition here because `events` module does
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* not depend on `core` module (and should not).
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*/
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using Tag = int32_t;
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public:
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static std::recursive_mutex &DispatchMutex();
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EventEmitter(
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SharedEventTarget eventTarget,
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Tag tag,
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WeakEventDispatcher eventDispatcher
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);
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virtual ~EventEmitter() = default;
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/*
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* Indicates that an event can be delivered to `eventTarget`.
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* Callsite must acquire `DispatchMutex` to access those methods.
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* The `setEnabled` operation is not guaranteed: the `EventEmitter` cannot
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* be re-enabled after disabling; in this case, the method does nothing.
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*/
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void setEnabled(bool enabled) const;
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bool getEnabled() const;
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protected:
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/*
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* Initates an event delivery process.
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* Is used by particular subclasses only.
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*/
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void dispatchEvent(
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const std::string &type,
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const folly::dynamic &payload = folly::dynamic::object(),
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const EventPriority &priority = EventPriority::AsynchronousBatched
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) const;
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private:
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mutable SharedEventTarget eventTarget_;
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Tag tag_;
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WeakEventDispatcher eventDispatcher_;
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};
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} // namespace react
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} // namespace facebook
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