Thank you Klas!

That was excellent input and I managed after few trial&errors to find a recipe that works for me:

- Create language overrides

- Add definitions in template index.php, just above the HEAD

<?php
JText::script('PH_ARTICLE_TITLE');
JText::script('PH_ARTICLE_LABEL1');
JText::script('PH_ARTICLE_LABEL2');
...
?>

</head>

- Add a simple code snippet in Script (JS) of the field

$("#art_title_backend").attr("placeholder", Joomla.JText._('PH_ARTICLE_TITLE'));

Similar code can be placed in other text fields, inserting/substituting just the field name and the override string.

P.S. Of course, since there is no need to duplicate override strings, it is perfectly ok to use COM_CCK_strings. However, as placeholders our labels can contain additional explanations, examples and so on.

Hey webcastor, Hey klas,

there is another trick with a css class and a litte jquery.

Regards,

RaSchDMD

Even though I haven't tested it, I suppose your solution is very nice for automation, but you skipped to say where do you put various language translations for placeholder. I imagine it should be some label (a label one language each) in the same group, that should be language constrained.

Hey webcastor,

the label is the placeholder. For example you put an "test" in it and you have a multilanguage site, the output of the placeholder is "COM_CCK_TEST". 

Then you have to translate it in your desired language files. In the english file en-GB.com_cck_default.ini with a COM_CCK_TEST="English test" and in the german file de-DE.com_cck_default.ini with a COM_CCK_TEST="Deutscher Test".

When you work only with one language, the output of the placeholder is "test" and you don‘t need to translate it.

Is it clear enough?

RaSchDMD