First and most important: Great project! Writing an editor must be a whole lot of work! Especially when source code analysis is included. You said that you're using clang there. I've also been working with clang (for more than two years by now) and I've got to say that it's a great tool when it comes down to source code analysis. It's a little hard to get into, but it's totally worth the effort - especially when templates are involved. You wouldn't wanna analyze such code on your own ;) So I think you don't regret using clang there, do you?

Now some feedback: - I really like how your file search and the file tree interact! - It would be nice to show the definitions of local variables (e.g. inside a function scope). Or even better: Highlight all usages that variable throughout the scope! That would really help keeping track of things.