Function CheckForMissingGlyphs

src/strings.cpp:2390–2466

* Check whether the currently loaded language pack * uses characters that the currently loaded font * does not support. If this is the case an error * message will be shown in English. The error * message will not be localized because that would * mean it might use characters that are not in the * font, which is the whole reason this check has * been added. * @param searcher The methods t

 *                  If nullptr the loaded language pack searcher is used.
 */
void CheckForMissingGlyphs(MissingGlyphSearcher *searcher)
{
	static LanguagePackGlyphSearcher pack_searcher;
	if (searcher == nullptr) searcher = &pack_searcher;
	bool bad_font = searcher->FindMissingGlyphs();
#if defined(WITH_FREETYPE) || defined(_WIN32) || defined(WITH_COCOA)
	if (bad_font) {
		/* We found an unprintable character... lets try whether we can find
		 * a fallback font that can print the characters in the current language. */
		bool any_font_configured = !_fcsettings.medium.font.empty();
		FontCacheSettings backup = _fcsettings;

		_fcsettings.mono.os_handle = nullptr;
		_fcsettings.medium.os_handle = nullptr;

		bad_font = !FontProviderManager::FindFallbackFont(&_fcsettings, _langpack.langpack->isocode, searcher);

		_fcsettings = std::move(backup);

		if (!bad_font && any_font_configured) {
			/* If the user configured a bad font, and we found a better one,
			 * show that we loaded the better font instead of the configured one.
			 */
			std::string err_str;
			StringBuilder builder(err_str);
			builder.PutUtf8(SCC_YELLOW);
			builder.Put("The current font is missing some of the characters used in the texts for this language. Using system fallback font instead.");
			ShowErrorMessage(GetEncodedString(STR_JUST_RAW_STRING, std::move(err_str)), {}, WL_WARNING);
		}

		if (bad_font) {
			/* Our fallback font does miss characters too, so keep the
			 * user chosen font as that is more likely to be any good than
			 * the wild guess we made */
			FontCache::LoadFontCaches(searcher->Monospace() ? FontSizes{FS_MONO} : FONTSIZES_REQUIRED);
		}
	}
#endif

	if (bad_font) {
		/* All attempts have failed. Display an error. As we do not want the string to be translated by
		 * the translators, we 'force' it into the binary and 'load' it via a BindCString. To do this
		 * properly we have to set the colour of the string, otherwise we end up with a lot of artifacts.
		 */
		std::string err_str;
		StringBuilder builder(err_str);
		builder.PutUtf8(SCC_YELLOW);
		builder.Put("The current font is missing some of the characters used in the texts for this language. Go to Help & Manuals > Fonts, or read the file docs/fonts.md in your OpenTTD directory, to see how to solve this.");
		ShowErrorMessage(GetEncodedString(STR_JUST_RAW_STRING, std::move(err_str)), {}, WL_WARNING);

		/* Reset the font width */
		LoadStringWidthTable(searcher->Monospace() ? FontSizes{FS_MONO} : FONTSIZES_REQUIRED);
		return;
	}

	/* Update the font with cache */
	LoadStringWidthTable(searcher->Monospace() ? FontSizes{FS_MONO} : FONTSIZES_REQUIRED);