So I've added a Cairo Win32 example of capturing MIDI controller changes and painting envelopes on the screen. The data is captured in real-time but the drawing is done based on a timer. The source code is very oddball for sure, but it kinda works, so hey.. :P
A screenshot: http://i.imgur.com/19vKa.png The bars fade in as time progresses, that's some 2011 HD eye candy for you there.