There is a button that looks like a demister on the dash beside the VDC button that I have no idea what it does. There is already demister buttons else ware in the car so it must be something different.
The Subaru Legacy owner's manual indicates that button is your windshield wiper deicer. Pictured below is part of page 3-38 of the manual. The manual explains how to use the deicer in this picture.