Hi Arthur,
Sorry you did not get any feedback for your issue after so long, shows there must be a minimal use or understanding of this class. Did you get help or find solution you can share. I'm also trying to find help using this class and lack of doc is still there I'm afraid.

One possibility is to look at KoTextDocumentLayout.h and cpp files, these might help with some information.

https://github.com/JeremiasE/KFormula/blob/gsoc/libs/kotext/KoTextDocumentLayout.h