Obel Statechart

You can think of statechart(SC) as kind of event-driven behavior tree (BT). But actually SC is more powerful and has more benefits than traditional BT.

This impls of SC is ported from well-known statechart JS implementation - XState. For more details on statechart, please refer to the xstate docs.

Statechart implemented by ECS

Statechart Component

A Statechart (SC) is an advanced form of event-driven Behavior Tree (BT) that offers enhanced capabilities and flexibility. This implementation is based on XState, a popular JavaScript statechart library. For comprehensive documentation, visit the XState documentation.

ECS Implementation

Components

The Statechart Component (SCCmpt) is composed of four main components:

1. Context Component

   • Implements a Rust enum-based JSON-like data structure
   • Provides CRUD operations for state management

2. State Node Component

   • Uses a cache-friendly double-linked array list structure
   • Optimized for efficient state transitions between nodes

3. Incoming Mailbox Component

   • Functions as a queue for received events
   • Manages event reception and processing

4. Outgoing Mailbox Component

   • Serves as a queue for events to be sent
   • Handles event distribution

System Architecture

1. Incoming Mailbox System

Functionality:

• Processes events sequentially
• Executes event handler functions
• Manages state node transitions

Concurrency Features:

• Multi-threaded execution utilized with all cpu cores
• Automatic components load balancing to prevent thread starvation
• Dedicated system group for sequential runs of systems

2. Outgoing Mailbox System

• Derived events are stored in the outgoing mailbox component
• System collects and routes events to appropriate incoming mailboxes
• Target entities receive events via their incoming mailbox components
• Incoming mailbox system processes new events