Mercury: A Messaging Framework for Modular UI Components

In recent years, the entity--component--system pattern has become a fundamental feature of the software architectures of game-development environments such as Unity and Unreal, which are used extensively in developing 3D user interfaces. In these systems, UI components typically respond to events, requiring programmers to write application-specific callback functions. In some cases, components are organized in a hierarchy that is used to propagate events among vertically connected components. When components need to communicate horizontally, programmers must connect those components manually and register/unregister events as needed. Moreover, events and callback signatures may be incompatible, making modular UIs cumbersome to build and share within or across applications. To address these problems, we introduce a messaging framework, Mercury, to facilitate communication among components. We provide an overview of Mercury, outline its underlying protocol and how it propagates messages to responders using relay nodes, describe a reference implementation in Unity, and present example systems built using Mercury to explain its advantages.