Unfortunately, using the Python object requires a separate installation of Python. While it is true that many users already have Python installed, many others do not and for such users the Python solution will error. In contrast, the solution that I presented above is based on the built-in waitfor function, and therefore works for all users.

I discussed Ctrl-C interrupts here: http://undocumentedmatlab.com/blog/mex-ctrl-c-interrupt

myevent = py.threading.Event();

And then making the object available to all interested parties (through appdata, parameter passing, etc.).
The object’s set(), is_set(), clear(), and wait() functions work quickly and reliably in MATLAB, and the wait() function takes a timeout parameter and returns a Boolean value that is true unless the timeout was reached.

The code that is launched by the button callback runs on a separate thread so waitfor simply blocks execution of that thread, and other callbacks can still process. This is actually documented in waitfor‘s documentation. I suggest to modify the callback code by disabling the button to prevent additional button clicks while one callback is blocked:

function cbf(hButton,~)
  set(hButton,'Enable','off');
  waitfor(msgbox(...))
  set(hButton,'Enable','on');
end

I stumbled onto this page when trying to solve my conundrum. I’m trying to get ‘waitfor/uiwait’ to hold for a message box in a callback. I made a minimum working example like this:

function foo()
uicontrol('style','push','string','push','callback',@cbf,'parent',figure);

function cbf(~,~)
h = msgbox('press ok to continue');
waitfor(h)

But no matter what I do, the waitfor is not respected, that is the pushbutton is not blocked so one can open as many msgboxes as one likes. Very odd behaviour I think, have you by any chance encountered issues like this before?

This is not surprising. Matlab’s computational engine is [still] single threaded. I hope and expect this will change in the future. Even when it does, I’m not sure that the listeners would be dispatched asynchronously. I can think of quite a few use-cases where the synchronous listener invocation is actually intended.

based on this, I presume that matlab is executing all of these callbacks in a single thread, and the dispatcher for the event source is just executing the listeners in order, so that it can’t process the next until the prior one returns?

@Marc – however, you can still use waitfor with Java objects