One thing you can do is to translate the constant values at your will, but still the language is going to be "English". Κάντο με UTF8 αν δε σε νοιάζει να χρησιμοποιήσεις άλλη γλώσσα. It is not the best solution if you need multilanguage content.
I also tried the above:
I have my content settings with two languages, Greek and English, but currently I need to use only Greek. So I don't want to enable multilanguage content yet, neither two menus nor the URLs to use the "en" or "el" suffixes. Supposing I use only the Greek language, I need to translate Vehicle Manager but not change o loose the English contants, to use them later.
I created a Greek.php as a copy to English.php, with lang_code 'el-GR' and placed it into components/com_vehiclemanager/lang folder. In VehicleManager :: Language Manager it saw the Greek (Ελληνικά) constants, but in back/frontend it still uses the English constant values.
In documentation it says that the site selected language is used, but the values are read from English.
Searching for a solution I tried to add into DB laguage table, Greek as in Joomla content language is set. The whole Vehicle Manager interface changed to constants and not constant values, as it did not read the Greek.php.
Another try was to change vehiclemanager.php (admin and component)
from
if ($languagelocale == ''
$languagelocale = "en-GB";
to
if ($languagelocale == ''
$languagelocale = "el-GR";
so in my site that no language suffixes are used, to make Greek lang_code as default. Nothing happened.
Is there any way to make it use as default my custom contant values?
Thanks in advance,
Johnny