I'm planning to write the long-awaited Tkinter Internals section of the docs. (https://github.com/python/cpython/blame/master/Doc/library/tk.rst#L48) I've spent too much time at this point to let it all go down the memory hole. Unfortunately, I don't know how ALL of the internals work. Is there someone else we could add to nosy that might be interested in writing some subsections?

Also, should this extended docs contribution be a new issue or rolled in with this one? Much abbreviated documentation of the new methods in this PR could be added to tkinter.rst. The new docs issue would be dependent on this issue since I won't be able to complete the docs until we have finished discussing what the future behavior of threads waiting for `dispatching` will be (error & poll vs Tcl_ConditionWait).