Editor framework

why not go with something like c#? it only works on windows, but yeah... chances are your development machine is a windows pc. c# comes with a UI framework and setting up a DX/XNA renderer isn't a lot of work.

might be a totally stupid suggestion :)

WPF is also good for making fast UI's it take a little more work that plain winforms tho

honestly you cant go wrong with what wiegje said

The engine is Windows and Linux with OpenGL for rendering. Whichever framework I use, I need a way to have actual engine render windows fit properly within the MDI interface, and still allow the engine to creates its own GL contexts and have its own main event loop and threading. Would be nice that the tools are cross-platform as well, but it's not completely necessary so I would accept going only with Windows-specific tools interface.

Maybe rather than adding a tools UI to the engine, I should allow the engine to remain a separate process and have the tool stuff as another application which itself can be Windows-only, but but then I'm not sure how to make the engine have render windows within the tools application's MDI parent window, and transfer messages and share data structures. I have some experience with Windows event-based IPC, but not sure if this is the best approach.

ah, well then have you taken a look at CEGUI? its a gui framework for opengl. people i know that work with it praise it like the second coming. you could integrate your editor in your engine like that.