WebAPI/PresentationAPI:CoreService

Introduction

The page explains the implementation detail of core service.

Architecture

PresentationService

A mediator among WebAPI classes, IPC and |PresentationSessionInfo|.

Live in chrome process.

PresentationSessionInfo

Maintain grotty details around session transports, receiver page and connection state.

Session infos use the established control channel to negotiate the SDP of session transport and create a transport builder to do the transport establishment.

Two subclasses, |PresentationControllingInfo| and |PresentationPresentingInfo|, stands for the controller and presenter. Presenting info will establish the transport after the receiver's page ready.

Live in chrome process.

PresentationSessionTransport

Maintain the underlying transport. We have TCP transport now and work on RTCDataChannel transport.

TCP transport lives in Chrome process. RTCDataChannel lives with the DOM. That is, live in content process in e10s mode.

PresentationIPCService

A mediator between IPC and WebAPI. Also manage PresentationIPCSessionInfo if the underlying transport is RTCDataChannel.

Only lives in e10s mode and in content process.

PresentationIPCSessionInfo

Manage PresentationDataChannelSessionTransport.

Only lives in e10s mode and in content process.

Call Flow Example

Establishing OOP RTCDataChannel Transport

Since RTCDataChannel should be accompanied with DOM, we should build our transport in content process in the case. Here's the procedure:

1. Hook handler: |SendRegisterTransportBuilderHandler| in |PresentationIPCService::StartSession| (sender) and |PresentationIPCService::NotifyReceiverReady| (receiver) hook a handler (|PresentationParent|) to |PresentationService| which lives in the chrome process.
2. Create a session transport builder: As chrome process ready (receive control channel|NotifyOpened| for sender; receive control channel |OnOffer| and receiver page ready |NotifyResponderReady| for receiver), |PresentationSessionInfo| create a transport builder to establish a transport.
3. Build a transport in content process: The transport builder is |PresentationParent| hooked by first step. It will triggered an IPC call to |PresentationIPCService| and build the underlying RTCDataChannel in the content process. It will call back to |PresentationService| the result of building.