- Add i18n/ module: imgui_i18n.h (Tr() macro + stub when disabled),
imgui_i18n.cpp (lookup table, Meyers singleton, placeholder substitution),
locale/zh_CN.cpp (Simplified Chinese translation table),
tools/extract_strings.py (helper to extract translatable strings)
- Opt-in via IMGUI_DEMO_ENABLE_I18N build flag; without it Tr(s) expands
to (s) at compile time with zero overhead and no extra dependencies
- See i18n/README.md for integration guide and how to add a new language
