Development Guide

This document explains how to continue development on jrpm. All patterns are based on actual code implemented in this project (cross-reference with commits in git log).

Code Organization Quick Reference

Directory	Responsibility
src/	All C++ source code (top-level named by system: rail_cmd.cpp, group_gui.cpp...)
src/network/	Networking (server/client/UDP/HTTP/content download)
src/script/	Script framework (Squirrel); api/ for AI/GS API classes
src/table/settings/*.ini	Setting definition sources (settingsgen generates code)
src/lang/english.txt	String definitions (strgen generates)
src/sl/saveload_common.h	Save version (SLV) enum
bin/ai/	AI scripts (GlobalAI is an example)

Common Development Patterns

• Adding a Game Command: Command enum + DEF_CMD_TUPLE_NT + handler + GUI/console entry point
• Adding a Script API: script_*.hpp/.cpp (auto-registers Squirrel bindings)
• Adding a Setting: .ini + settings_type.h field + string

Building

cmake -B build ..
cmake --build build -j

Development Notes

1. Encoding: When modifying source code/documentation containing Chinese characters, ensure UTF-8 (the Write/Edit tool on this machine may produce GBK encoding; use jgrpp-features/_fix_utf8.py to fix);
2. Commit messages: Recommended to use English (to avoid terminal encoding issues);
3. Inserting into command enum mid-sequence shifts subsequent command IDs — old binary versions will be inconsistent with new versions in multiplayer; this is normal within a fork, upgrade must be synchronized;
4. Save version: When modifying save structure, add a new SLV_* entry in src/sl/saveload_common.h and update SAVEGAME_VERSION;
5. New files: .cpp must be added to the corresponding CMakeLists.txt source list (src/CMakeLists.txt or subdirectory/script/api/CMakeLists.txt); script_*.hpp is auto-discovered by file(GLOB), no registration needed;
6. New strings: Add to src/lang/english.txt (other languages fall back to English);
7. NewGRF/save compatibility: Changing _openttd_content_version / NewGRF version number needs caution (affects multiplayer and content compatibility).

Regression Testing Suggestions (Important)

The current branch has not been compiled on a real machine. After the first build, it is recommended to test in this order:

1. Basic: openttd-jrpm -v shows jrpm-0.1.0;
2. Save: single-player run for 1-2 game years;
3. Multiplayer: jrpm clients connect to each other; jgrpp/pxp clients join;
4. New features: train decoupling (decouple/couple/reverse), modular airports (modify layout), parallel download, auto-grouping, build tooltip, GlobalAI;
5. Legacy feature regression: signals, tracerestrict, scheduled dispatch, template replacement.