Memory leaks when read/write to DOM

[jpn]

I first started by not allocate anything on the heap. But it leaked memory.

How did you verify this?

I very much would like to not allocate anything on the heap, but am not sure how & were the objects goes out of scope?

Well, that's something fundamental you just have to know about the programming language you use before you even start working with a toolkit like Qt. I suggest you refer to your favourite C++ book (notice that there are free and online books out there, you might want to search the forums for those).