Maybe you have seen this effect already used by Google, espicially in Google Translate, and YouTube. Whenever you change the input language on forms input, for example, to Arabic, and start typing, the direction of the text field changes to match the language natural direction.
Auto Input Text Direction is a little JavaScript function that I wrote, it detects the input language on html forms, and changes the input direction based on the language, i.e., right to left for the Arabic language, Thus, emulating Google's effect.
For more information, please visit the article where I explain its functionality.