DCS Scratchpad is a Lua-based mod for Eagle Dynamics' DCS World flight simulator that provides an in-game, resizable, and movable scratchpad for taking persistent notes. The mod allows users to create and switch between multiple text pages, insert coordinates from the F10 map interface, and persist all notes to text files in the user's saved games directory. It integrates with DCS World through Lua simulation callbacks to manage the UI state and handle user interactions. The mod features an extension system that enables additional functionality such as virtual keyboards, aircraft-specific startup procedures, message logging, and coordinate formatting tools. Extensions are loaded from Lua files in a designated directory and receive a well-defined API for interacting with the scratchpad UI, including adding buttons, registering coordinate listeners, and manipulating text content. This architecture allows for community-contributed enhancements while maintaining core functionality. Key technical highlights include robust UTF-8-aware text manipulation for proper cursor positioning and text insertion, sophisticated geographic coordinate formatting supporting multiple representations (DMS, DDM, Decimal Degrees), and a sandboxed extension loading mechanism that provides isolation between extensions and the core mod. The implementation demonstrates attention to detail in handling edge cases related to international text, coordinate systems, and user interface interactions.

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