像Mail.app回复视图中的UITextView

In the iOS Mail app when you hit reply, you are presented with a text view like this. The vertical blue line keeps growing or shrinking (as the case may be) when you try to edit the previous reply while doing an inline reply or something. The top portion (your main reply) looks normal. Any idea on a really top level on how to pull this kind of text view off?In the iOS Mail app when you hit reply, you are