Change: treat languages as finished, if translations are 75% completed.

Unfinished translations are not auto-picked from the locale.
In release builds, unfinished translations are not offered in the GUI.
Unfinished translations are available in non-release builds, or by editing openttd.cfg.

src/language.h

@@ -58,6 +58,7 @@ struct LanguagePackHeader {
 	char cases[MAX_NUM_CASES][CASE_GENDER_LEN];     ///< the cases used by this translation
 
 	bool IsValid() const;
+	bool IsReasonablyFinished() const;
 
 	/**
 	 * Get the index for the given gender.

src/settings_gui.cpp

@@ -218,6 +218,7 @@ struct GameOptionsWindow : Window {
 
 			case WID_GO_LANG_DROPDOWN: { // Setup interface language dropdown
 				for (uint i = 0; i < _languages.size(); i++) {
+					if (IsReleasedVersion() && !_languages[i].IsReasonablyFinished()) continue;
 					auto item = new DropDownListParamStringItem(IsReleasedVersion() || _languages[i].missing < _settings_client.gui.missing_strings_threshold ? STR_JUST_RAW_STRING : STR_GAME_OPTIONS_LANGUAGE_PERCENTAGE, i, false);
 					if (&_languages[i] == _current_language) {
 						*selected_index = i;

src/strings.cpp

@@ -1718,6 +1718,15 @@ bool LanguagePackHeader::IsValid() const
 	       StrValid(this->digit_decimal_separator,        lastof(this->digit_decimal_separator));
 }
 
+/**
+ * Check whether a translation is sufficiently finished
+ * to offer it to the public.
+ */
+bool LanguagePackHeader::IsReasonablyFinished() const
+{
+	return 4 * this->missing < LANGUAGE_TOTAL_STRINGS;
+}
+
 /**
  * Read a particular language.
  * @param lang The metadata about the language.
@@ -1972,6 +1981,10 @@ void InitializeLanguagePacks()
 		}
 
 		if (strcmp (lng.isocode, "en_GB") == 0) en_GB_fallback    = &lng;
+
+		/* Only auto-pick finished translations */
+		if (!lng.IsReasonablyFinished()) continue;
+
 		if (strncmp(lng.isocode, lang, 5) == 0) chosen_language   = &lng;
 		if (strncmp(lng.isocode, lang, 2) == 0) language_fallback = &lng;
 	}