README

Shared pointers

Do not keep ImageRef or any kind of smart pointer to doc:: entities. As several cmd can persist in parallel with other cmd (due the tree structure of the undo history) these smart pointers can generate conflicts in the logic layer. E.g. If we keep an ImageRef inside a cmd, the image is not removed from the objects hash table, so two or more cmd could try to add/remove the same object in the hash table (there are asserts to check this state, were someone is trying to add the same ObjectId in the hash table).