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// Copyright 2014 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 PPAPI_CPP_MESSAGE_HANDLER_H_
#define PPAPI_CPP_MESSAGE_HANDLER_H_
namespace pp {
/// <code>MessageHandler</code> is an abstract base class that the plugin may
/// implement if it wants to receive messages from JavaScript on a background
/// thread when JavaScript invokes postMessage() or
/// postMessageAndAwaitResponse(). See pp::Instance::RegisterMessageHandler()
/// for usage.
class MessageHandler {
public:
virtual ~MessageHandler() {}
/// Invoked as a result of JavaScript invoking postMessage() on the plugin's
/// DOM element.
///
/// @param[in] instance An <code>InstanceHandle</code> identifying one
/// instance of a module.
/// @param[in] message_data A copy of the parameter that JavaScript provided
/// to postMessage().
virtual void HandleMessage(pp::InstanceHandle instance,
const Var& message_data) = 0;
/// Invoked as a result of JavaScript invoking postMessageAndAwaitResponse()
/// on the plugin's DOM element.
///
/// NOTE: JavaScript execution is blocked during the duration of this call.
/// Hence, the plugin should respond as quickly as possible. For this reason,
/// blocking completion callbacks are disallowed while handling a blocking
/// message.
///
/// @param[in] instance An <code>InstanceHandle</code> identifying one
/// instance of a module.
/// @param[in] message_data A copy of the parameter that JavaScript provided
/// to postMessage().
/// @return Returns a pp::Var that is then copied to a JavaScript object
/// which is returned as the result of JavaScript's call of
/// postMessageAndAwaitResponse().
virtual pp::Var HandleBlockingMessage(pp::InstanceHandle instance,
const Var& message_data) = 0;
/// Invoked when this MessageHandler is no longer needed. After this, no more
/// calls will be made to this object.
///
/// @param[in] instance An <code>InstanceHandle</code> identifying one
/// instance of a module.
virtual void WasUnregistered(pp::InstanceHandle instance) = 0;
};
} // namespace pp
#endif // PPAPI_CPP_MESSAGE_HANDLER_H_