Gnome Canvas vs Cairo
As great as Cairo seems, I just recently learned about a widget in the gnome / GTK+ library that can also be used for drawing: Gnome Canvas. While Cairo seems to be more for drawing static, non-interactive pictures, the Gnome Canvas is more for layering shapes, bitmaps, etc... onto a "canvas", and it keeps track of which shape is clicked on, allows for drag 'n drop, and only re-draws the part of the canvas that is changing.
(Here is an examlpe of the Gnome Canvas being used):
Now I'm not so sure which is the best technology to use for my video editor timeline. Cairo seems more powerful (i.e. supports all sorts of cool vector drawing techniques), the Gnome Canvas seems more practical, since it wraps all the hard work up (such as tracking items). Also, did discover that someone created a Cairo Canvas widget... although I haven't had time to research it yet.