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The Care and Feeding of WebCore Modules


As we add more features to WebCore, the project becomes more complex. Some self-contained features, like IndexedDB and MediaStream, expose DOM interfaces but aren't otherwise involved in the core functionality of the engine, such as layout and rendering. The module system let us reduce the complexity of the project by loosening the coupling of between these features and the rest of WebCore.

This document describes how WebCore's module system works and how to leverage it when building a new feature.

Dependency diagram

The code for a module belongs in a subdirectory of the Modules directory and in a subdirectory of WebCore/platform. For example, the MediaStream module is contained in and

Keeping the code for your feature in a single directory reduces the burden that your feature places on other WebKit contributors as they develop other modules and core functionality of the engine. This dependency diagram shows how the WebAudio, MediaStream, and IndexedDB modules fit into the WebKit's dependency diagram. Notice, in particular, that WebCore proper should not have dependencies on your module.

Associating JavaScript APIs with "core" objects

Associating state with "core" objects

Observing the lifecycle of "core" objects

Adding new events and exceptions