Message handlers are no longer cleared

[alxbilger]

Currently, the following code is not working as expected:

with MessageHandler() as msg_handler:
    SofaRuntime.init()
    # emit a message so it is captured by msg_handler

This is because SofaRuntime.init() removes all the messages handlers, including msg_handler. The consequence is that the emitted messages are not captured by msg_handler.

Instead of removing all the message handlers, I suggest to remove only MainConsoleMessageHandler.

If it's necessary to remove all the message handlers, a binding has been introduced in #588.

[damienmarchal]

You are right the presented code does not work.

Because the dispatcher is a singleton of Sofa, the SofaRuntime.init() is supposed to be called before MessageHandler()... because SofaRuntime is actually the API that manipulates the singleons.

To fix this I would be more in favore or designing the API so it is clear that MessageHandler is actually doing something on the "runtime" singletons. Maybe moving the MessageHandler into SofaRuntime... .

[alxbilger]

the SofaRuntime.init() is supposed to be called before MessageHandler()

I agree but I am in this situation because of unit testing of Python scripts. The Python script calls SofaRuntime.ini() (or not, it's up to the script developer), and I insert a message handler before calling the script.

I am not satisfied by this PR so far. It needs more thinking.