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

content/renderer/presentation/presentation_connection_proxy.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 CONTENT_RENDERER_PRESENTATION_PRESENTATION_CONNECTION_PROXY_H_
+#define CONTENT_RENDERER_PRESENTATION_PRESENTATION_CONNECTION_PROXY_H_
+
+#include "base/callback.h"
+#include "mojo/public/cpp/bindings/binding.h"
+#include "third_party/WebKit/public/platform/modules/presentation/WebPresentationConnection.h"
+#include "third_party/WebKit/public/platform/modules/presentation/WebPresentationConnectionProxy.h"
+#include "third_party/WebKit/public/platform/modules/presentation/presentation.mojom.h"
+
+namespace content {
+
+// This class connects PresentationConnection owned by one frame with
+// PresentationConnection owned by a different frame.
+//
+// |SetSourceConnection| sets |source_connection_| to PresentationConnection
+// object owned by current frame.
+// |SetTargetConnection| sets |target_connection_| to mojo handle of
+// PresentationConnection object owned by a different frame.
+//
+// When both |source_connection_| and |target_connection_| are set,
+// we can send message or notify state changes between controller and receiver.
+//
+// To send message from controlling frame to receiver frame:
+// 1. Controlling frame invokes connection.sendMessage();
+// 2. This call is delegated to controller presentation connection proxy's
+//    SendString().
+//      PresentationConnectionProxy::SendString() {
+//         target_connection_->OnConnectionMessageReceived();
+//      }
+// 3. Receiver PresentationConnectionProxy::OnConnectionMessageReceived() is
+//  invoked.
+// 4. connection.onmessage event on receiver frame is fired.
+//
+// Sending message from receiver frame to controlling frame and notifying state
+// changes works the same.
+//
+// Instance of this class is only created for offscreen presentations.
+class PresentationConnectionProxy
+    : public blink::WebPresentationConnectionProxy,
+      public NON_EXPORTED_BASE(blink::mojom::PresentationConnection) {
+ public:
+  PresentationConnectionProxy();
+  ~PresentationConnectionProxy() override;
+
+  blink::mojom::PresentationConnectionPtr Bind();
+
+  // WebPresentationConnectionProxy Implementation
+  void SetSourceConnection(
+      blink::WebPresentationConnection* connection) override;
+  void SendString(const blink::WebString& message) override;
+  void SendArrayBuffer(const uint8_t* data, size_t length) override;
+
+  // blink::mojom::PresentationConnection implementation
+  void SetTargetConnection(
+      blink::mojom::PresentationConnectionPtr connection) override;
+  void OnMessage(blink::mojom::SessionMessagePtr message) override;
+
+ private:
+  mojo::Binding<blink::mojom::PresentationConnection> binding_;
+  blink::mojom::PresentationConnectionPtr target_connection_;
+  blink::WebPresentationConnection* source_connection_;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_RENDERER_PRESENTATION_PRESENTATION_CONNECTION_PROXY_H_