Xcode 4 has a Focus code blocks on hover setting in Preferences > Text Editing.

When you hover the mouse on a Code folding ribbon, the mentioned setting has the effect shown in image below.
Also, the effect stays put when you navigate with the keyboard (even when you move focus to Assistant editor, Navigator, Utilities, ... but not to, say, Organizer or Version editor).
How could you add a key binding for this?
