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Daniel Nylander edited this page Aug 13, 2026 · 6 revisions

Internationalization

Updated for v1.1.126. The 19-language catalog and compiled message catalogs are synchronized as part of the release preparation.

OpenCaptive supports 19 languages with full UI translation coverage using a gettext-compatible PO file system.

Supported Languages

Code Language
en English
sv Svenska
cs Cestina
da Dansk
de Deutsch
es Espanol
fi Suomi
fr Francais
hu Magyar
it Italiano
ja Japanese
ko Korean
nl Nederlands
no Norsk
pl Polski
pt Portugues
ro Romana
ru Russian
zh Chinese

Architecture

Translation Macro

All translatable strings are wrapped with the _() macro:

#define _(s) i18n_get(s)

This calls i18n_get(), which performs a linear search through the loaded translation table (up to 512 entries of 256 characters each).

Data Structures

#define I18N_MAX_ENTRIES 512
#define I18N_MAX_MSGLEN 256

typedef struct {
    char msgid[I18N_MAX_MSGLEN];
    char msgstr[I18N_MAX_MSGLEN];
} I18nEntry;

typedef struct {
    char lang[16];
    I18nEntry entries[I18N_MAX_ENTRIES];
    int count;
} I18nTable;

API

void        i18n_init(const char *lang_override);
void        i18n_free(void);
const char *i18n_get(const char *msgid);
const char *i18n_get_lang(void);

Language Detection

At startup, i18n_init determines the language in this order:

  1. CLI override: --lang <code> command-line argument (passed as lang_override).
  2. SDL3 auto-detection: SDL_GetPreferredLocales() queries the operating system locale.
  3. Fallback: English (no PO file loaded; i18n_get returns the msgid verbatim).

PO File Format

Translation files use the standard gettext .po format, stored in the po/ directory:

  • Source files: po/<lang>.po (e.g., po/sv.po, po/ja.po)
  • Template: po/messages.pot (POT template for generating new translations)

The runtime loads .po files directly — no .mo compilation step is needed. The loader searches for PO files first relative to the SDL base path, then the current working directory. It handles escape sequences (\n, \t, \\, \") and multi-line msgid/msgstr via continuation strings.

Translation Coverage

All user-facing text is translatable:

  • Start menu labels and descriptions
  • Settings panel items
  • Building interaction dialogue
  • Shop interface
  • NPC dialogue
  • Combat messages
  • All HUD and status text

Font Rendering

Bitmap Font

The built-in bitmap font uses 5-column, 7-row glyphs covering A-Z, a-z, 0-9, and common punctuation. It includes:

  • UTF-8 decoding: multi-byte UTF-8 sequences are decoded to Unicode codepoints.
  • Accented character fallback: Unicode accented characters are mapped to their ASCII base character for rendering (e.g., e with accent maps to plain e).

TTF Font

The start menu uses DejaVu Sans Mono Bold TTF rendering at 36pt, 18pt, and 14pt sizes, which supports the full Unicode range needed for all 19 languages.

Settings Integration

The language selector in the Settings panel cycles through all 19 languages using Left/Right arrow keys. The lang_index field in StartMenu tracks the current selection. Changing the language reloads the translation table.

Adding a New Language

  1. Copy po/messages.pot to po/<code>.po.
  2. Translate all msgstr entries.
  3. Add the language code to the LANG_COUNT array in start_menu.c.

Source Files

  • Header: include/i18n.h
  • Implementation: src/data/i18n.c
  • Translations: po/*.po
  • Template: po/messages.pot

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