SDL Game Engine Integration into Qt Game Editor

Hello,

I have a design problem about Qt+SDL and would be thankful for any help.

Currently, I am developing a game using SDL, pushed its engine to alpha state, and like to create an editor with Qt next. As this is my first serious GUI project, and after poking around with some toolkits, I chose Qt, but are still confused how to tackle the design, and stuck with following problem:

How to integrate the game engine into Qt and use it to edit game object (sprites, tiles, etc.)?

The idea is to reduce/eliminate duplication, and have the same output when editing or playing.

My approach would be something like this (if it's possible, but I don't know):

Game data is saved within an XML file.
The engine parses to renders the game.
The editor plays the game, and parses data to create editing objects around game objects (e.g. boxes to drag & drop sprites).
The game itself needs a player to start (still has to be written).

Hope this rough description is detailed enough to be able to relate the problem.

Your opinion about this problem & solution, as well as alternatives and references, will be a great help to me.

Thanks for your patience
Michael