All three boxes are editable. You can focus them and move the caret around.

I have an overlay in the padding. No matter how much text there is, it's all good, because I'm auto-height. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Etiam molestie, orci eu porttitor euismod, augue odio porttitor velit, sit amet blandit nisi nunc id sem.
The End.
I have an overlay in the padding, and I'm underfilled. All is good if I stay short.
The End.
I have an overlay in the padding, and overfilled. You can reveal the end of the text by scrolling, but not by moving the caret. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Etiam molestie, orci eu porttitor euismod, augue odio porttitor velit, sit amet blandit nisi nunc id sem.
The End. Keep typing here...