Today I implemented an oft-requested feature for MonoDevelop: making the code completion and info tooltips transparent when the Control key is held down. This enables you to take a look at the code that the window’s obscuring, without dismissing the popup.
This feature’s in MonoDevelop trunk, and can be tried out right away. You’ll need GTK+ 2.12 or above (GTK# only needs to be 2.8 or above) and Compiz or any other compositing window manager. It’s also available in my MonoDevelop trunk builds on the openSUSE build service.
This behaviour is encapsulated in a class that can be attached to any Gtk.Window, and handles a couple of nasty hacks and workarounds.