[Presentation API] (alternative) 1-UA: send message between controller and receiver page

chrome/browser/media/router/offscreen_presentation_manager.h

+// Copyright 2016 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 CHROME_BROWSER_MEDIA_ROUTER_OFFSCREEN_PRESENTATION_MANAGER_H_
+#define CHROME_BROWSER_MEDIA_ROUTER_OFFSCREEN_PRESENTATION_MANAGER_H_
+
+#include <map>
+#include <memory>
+#include <string>
+
+#include "base/macros.h"
+#include "base/threading/thread_checker.h"
+#include "chrome/browser/media/router/render_frame_host_id.h"
+#include "components/keyed_service/core/keyed_service.h"
+#include "content/public/browser/presentation_service_delegate.h"
+
+class GURL;
+
+namespace media_router {

[mark a. foltz, 2016/10/08 00:33:41]

From a layering point of view I wonder if this belongs in chrome/browser or
content/browser.   It doesn't actually depend on the media router, which is a
good thing.

However content/browser doesn't seem to have the concept of profile-keyed
services, and we need an object that is tied to the browser context and not a
specific frame/renderer client.  I looked briefly for a similar use case and
didn't find anything obvious.  Maybe chrome/browser is the right place, but in a
parallel folder to the media_router?

Derek, do you have any thoughts?

[zhaobin, 2016/10/12 02:27:32]

Leave it in media/router folder for now. We will move it later when necessary.

+
+// Instances of this class manages all offscreen presentations started in the
+// associated Profile and facilitates communication between the controllers and
+// the receiver of an offscreen presentation.
+//
+// Example usage:
+//
+// (PresentationConnectionPtr - blink::mojom::PresentationConnectionPtr, mojo
+//  handler for blink::PresentationConnection object in render process)
+//
+// Receiver is created to host the offscreen presentation and registers itself
+// so that controller frames can connect to it:
+//
+//   OffscreenPresentationManager* manager =
+//       OffscreenPresentationManagerFactory::GetOrCreateForBrowserContext(
+//           Profile::FromBrowserContext(web_contents_->GetBrowserContext())

[mark a. foltz, 2016/10/08 00:33:41]

Where does |web_contents_| come from here?  Is it from the controller's page?

[zhaobin, 2016/10/12 02:27:33]

For controller, it is from controller's page;
For receiver, it is from offscreen tab, but calls GetOriginalProfile() to get
the same profile as controller.

(controller) In PresentationServiceDelegateImpl's contructor:

offscreen_presentation_manager_(
          OffscreenPresentationManagerFactory::GetOrCreateForBrowserContext(
              web_contents_->GetBrowserContext()))


(receiver) In ReceiverPresentationServiceDelegateImpl's constructor:

offscreen_presentation_manager_(
          OffscreenPresentationManagerFactory::GetOrCreateForBrowserContext(
              Profile::FromBrowserContext(web_contents_->GetBrowserContext())
                  ->GetOriginalProfile())) {

+//                  ->GetOriginalProfile());

[mark a. foltz, 2016/10/08 00:33:41]

Nit: the factory should take care of returning the manager for any browser
context, so this would be

OffscreenPresentationManagerFactory::GetOrCreateForBrowserContext(
    web_contents_->GetBrowserContext())

[zhaobin, 2016/10/12 02:27:33]

Done.

+//   manager->RegisterOffscreenPresentationReceiver(presentation_id,
+//       base::Bind(&PresentationServiceImpl::OnReceiverConnectionAvailable));

[mark a. foltz, 2016/10/08 00:33:41]

Should this be bound to the instance of the PSImpl from the receiver's page?
How does the controller get access to this instance?

[zhaobin, 2016/10/12 02:27:32]

Yes.

The object is bind to the function:

delegate_->RegisterReceiverAvailableCallback(
       base::Bind(&PresentationServiceImpl::OnReceiverConnectionAvailable,
                  weak_factory_.GetWeakPtr()));

And callback in invoked in OffscreenPresentationManager, which have access to
controller PresentationConnectionPtr and receiver callback:

OffscreenPresentationManager::OffscreenPresentation::RegisterReceiver()
OffscreenPresentationManager::OffscreenPresentation::RegisterController()

+//   ...

[mark a. foltz, 2016/10/08 00:33:41]

I would add a comment here like, 

// Invoked on receiver's PresentationServiceImpl when controller connection is
established

[zhaobin, 2016/10/12 02:27:33]

Done.

+//   void PresentationServiceImpl::OnReceiverConnectionAvailable(
+//       const content::PresentationSessionInfo& session,
+//       PresentationConnectionPtr&& controller) {
+//     [Create a PresentationConnection on receiver page.
+//      Connect receiver PresentationConnectionPtr with controller
+//      PresenatationConnectionPtr]

[mark a. foltz, 2016/10/08 00:33:41]

Typo

[zhaobin, 2016/10/12 02:27:32]

Done.

+//     client_->OnReceiverConnectionAvailable();
+//   }
+//
+// Controller frame establishes connection with the receiver side, resulting
+// in a connection with the two endpoints being the controller
+// PresentationConnectionPtr and receiver PresentationConnectionPtr.
+// Note calling this will trigger receiver frame's
+// PresentationServiceImpl::OnReceiverConnectionAvailable.
+//
+//   manager->RegisterOffscreenPresentationController(
+//           presentation_id, controller_frame_id, controller_ptr);
+//
+// Send message from controller/receiver to receiver/controller:
+//
+//   In controller's (or receiver's) PresentationConnctionPtr::SendString() {
+//     ...
+//     target_connection_->OnSessionMessageReceived();
+//   }
+//
+// A controller or receiver leaves the offscreen presentation (e.g.,
+// due to navigation) by unregistering themselves from
+// OffscreenPresentationConnection object.
+//
+// When the receiver is no longer associated with an offscreen presentation, it
+// shall remove itself from associated controllers and then unregister itself
+// with OffscreenPresentationManager. Unregistration will prevent additional
+// controllers from establishing a connection with the receiver:
+//
+//   In receiver's PSImpl::Reset() {
+//     for (controller : offscreen_presentation_observers_)
+//       controller->RemoveOffscreenPresentationClient(receiver);
+//   }
+//   manager->UnregisterOffscreenPresentationReceiver(presentation_id);
+//
+// This class is not thread safe. All functions must be invoked on the UI
+// thread. All callbacks passed into this class will also be invoked on UI
+// thread.
+class OffscreenPresentationManager : public KeyedService {
+ public:
+  ~OffscreenPresentationManager() override;
+
+  // Registers controller PresentationConnectionPtr to presentation
+  // with |presentation_id|, |render_frame_id|.
+  // Creates a new presentation if no presentation with |presentation_id|
+  // exists.
+  // |controller| Not owned by this class.
+  void RegisterOffscreenPresentationController(
+      const std::string& presentation_id,
+      const GURL& presentation_url,
+      const RenderFrameHostId& render_frame_id,
+      content::PresentationConnectionPtr controller);
+
+  // Unregisters controller PSImpl to presentation with |presentation_id|,
+  // |render_frame_id|.
+  void UnregisterOffscreenPresentationController(
+      const std::string& presentation_id,
+      const RenderFrameHostId& render_frame_id);
+
+  // Registers receiverConnectionAvailablecallback to presentation
+  // with |presentation_id|.
+  void OnOffscreenPresentationReceiverCreated(
+      const std::string& presentation_id,
+      const GURL& presentation_url,
+      const content::ReceiverConnectionAvailableCallback& receiver_callback);
+
+  void OnOffscreenPresentationReceiverTerminated(
+      const std::string& presentation_id);
+
+ private:
+  // Represents an offscreen presentation registered with
+  // OffscreenPresentationManager.
+  // Contains callback to the receiver to inform it of new connections
+  // established from a controller.
+  // Contains set of controllers registered to OffscreenPresentationManager
+  // before corresponding receiver.
+  class OffscreenPresentation {
+   public:
+    explicit OffscreenPresentation(const std::string& presentation_id,

[mark a. foltz, 2016/10/08 00:33:41]

explicit is not needed for two-arg constructors

[zhaobin, 2016/10/12 02:27:33]

Done.

+                                   const GURL& presentation_url);
+    ~OffscreenPresentation();
+
+    void RegisterController(const RenderFrameHostId& render_frame_id,
+                            content::PresentationConnectionPtr controller);
+
+    void UnregisterController(const RenderFrameHostId& render_frame_id);
+
+    void RegisterReceiver(
+        const content::ReceiverConnectionAvailableCallback& receiver_callback);
+
+   private:
+    friend class OffscreenPresentationManagerTest;
+    friend class OffscreenPresentationManager;
+
+    // presentation_id for current presentation.
+    const std::string presentation_id_;
+
+    // URL for current presentation.
+    const GURL presentation_url_;
+
+    // Bind to receiver frame's
+    // PresentationServiceImpl::OnReceiverConnectionAvailable.
+    content::ReceiverConnectionAvailableCallback receiver_callback_;
+
+    // proxy to controller PSImpl
+    // It only contains controllers registered before receiver_callback_
+    // is set. This map will be cleared in RegisterReceiver().
+    std::unordered_map<RenderFrameHostId,
+                       content::PresentationConnectionPtr,
+                       RenderFrameHostIdHasher>
+        pending_controllers_;
+
+    DISALLOW_COPY_AND_ASSIGN(OffscreenPresentation);
+  };
+
+ private:
+  friend class OffscreenPresentationManagerFactory;
+  friend class OffscreenPresentationManagerTest;
+
+  // Used by OffscreenPresentationManagerFactory::GetOrCreateForBrowserContext.
+  OffscreenPresentationManager();
+
+  // Creates an offscreen presentation with
+  // |presentation_id| and |presentation_url|.
+  OffscreenPresentation* GetOrCreateOffscreenPresentation(
+      const std::string& presentation_id,
+      const GURL& presentation_url);
+
+  // Maps from presentation ID to OffscreenPresentation.
+  std::map<std::string, OffscreenPresentation*> offscreen_presentations_;
+
+  base::ThreadChecker thread_checker_;
+
+  DISALLOW_COPY_AND_ASSIGN(OffscreenPresentationManager);
+};
+
+}  // namespace media_router
+
+#endif  // CHROME_BROWSER_MEDIA_ROUTER_OFFSCREEN_PRESENTATION_MANAGER_H_