Unfortunately, after lots of testing/experimenting, I cannot find a way to make the correct call/s at the correct time. The methods that call the exit handlers directly or through InvokeExitHandlers are Tcl_Exit, Tcl_Finalize & FinalizeThread (Tcl_FinalizeThread) – Tcl_ExitThread calls Tcl_FinalizeThread.

We want to call the exit handlers (to access TkClipCleanup) with as little else as possible and both Tcl_Exit & Tcl_Finalize call FinalizeThread, so I concluded the method we should call is Tcl_FinalizeThread. Tcl_Finalize also stops the Python interpreter (not quite sure why), so this should only be called when the interpreter is stopping/stopped.

The problem with Tcl_FinalizeThread, is that it also finalises some of the mutexs (most notably asyncMutex - part of the async system). Once the mutexs are finalised, I can't find a way of creating them again (I think they are a global variables created on load), meaning that a new tcl interpreter cannot be created in the same thread (and even if it can, any calls to it cause the Python interpreter to crash).

This means we cannot call the Tcl_FinalizeThread method either when the root is destroyed or when the Tkapp object is deleted, as the user could still request a new tcl interpreter. This leaves us with only one option: call it when the Python interpreter is closing. For this, which call is made doesn’t really matter, and so to test, I commented out the "#if 0", to see if this call fixed the clipboard issue (if it had worked, we could have deleted all bindings before calling Tcl_Finalize). Unfortunately, this did not fix the clipboard issue and so I did not deem it worth developing an "unbinder" (possibly because the GC had already destroyed the interpreter?).

I did not even get onto the issue of multiple, simultaneous interpreters but unless someone has an idea that could solve any of the issues above (or we ask the Tcl team to make TkClipCleanup a public method!), I can’t see how we can patch this issue.