P: Guided transform lines that snap to edges

As an architectural photographer, I am constantly reaching for the fantastic guided transform tool to straighten things out. The one thing I can think of that would make the tool better would be if the lines automatically snapped to edges it sees in the photo. It would make setting the lines much easier using a laptop trackpad in particular, but even a mouse can be jumpy when you’re looking at the loupe view to snap your lines. Of course, I would want a modifier key to temporarily disable the snap feature if for any reason it wasn’t doing what I wanted.