I'm designing a form for multiple languages on mobile. in english the prefill text is not too long, but when the translations e.g. russian, what's the best way to handle when it ends up being longer than the width of the screen? Is truncation the only option?
It depends on what the purpose of the pre-fill is. Is it a placeholder ? Does it hold information on how the input should be filled ? What is the supported text length on it ? If it is pre-filled is it editable ?
In my opinion you should remove placeholders all together, have labels and add info text underneath the input if it shows conditions of how the input should be filled ( Eg. Password should have at least 6 characters ).