I ran into a Xcode debugging view I hadn't used before.

Instead of focusing on just one file, the main source editor (not just the navigator) showed detailed stack frames. I think the top of the source editor was the current frame and callers extended below, though I might have that backwards. I'm also unsure how much code appeared in each frame. Maybe the whole function?

What's this called and how do I turn it on intentionally? Was it added + removed in the betas? #Xcode