Friday, January 15, 2016

Architecture of the Web Inspector

Diego Pino García:

The Web Inspector is an important component of the WebKit project. It’s an application structured in 3 layers: a frontend, a backend and a target. This abstraction allows detaching the inspector from the target (inspected WebKit browser).

The frontend is a web application composed of HTML + CSS + JavaScript. It implements a Model-View-Controller pattern and makes heavy use of ECMA2015 features. The backend exposes information of WebKit’s WebCore and JavaScriptCore elements.

Communication between frontend and backend is provided by several dispatchers that communicate both parts through the WebKit Remote Debugging Protocol (a JSON-RPC 2.0 based protocol). The protocol defines several domains. Each domain defines commands and events which are the messages the frontend and the backend exchange with each other. Actual implementation of backend commands is provided by agent classes that live in WebCore and JavaScriptCore side. On the frontend side, several observer classes can listen and respond backend notifications.

Update (2016-01-16): Timothy Hatcher:

As the years progressed, we rapidly added to the tool — exposing more features and evolving the UI to adapt to new developer workflows. To commemorate the past 10 years of Web Inspector, we put together this timeline of major events and past blog posts for posterity.

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