Question: *Facts about MATLAB:*

1. MATLAB UI is Java Swing.
2. MATLAB has excellent interoperability with Java, it is possible to initialize Java objects and call their methods directly from MATLAB code, it is even possible to pass in MATLAB defined listeners to Java!

*My problem:*

MATLAB does not offer background threads, so to make MATLAB UI responsive we have to call function [drawnow](http://www.mathworks.de/help/techdoc/ref/drawnow.html) which flushes Swing EDT queue, see also [here](http://undocumentedmatlab.com/blog/matlab-and-the-event-dispatch-thread-edt/) and [here](https://stackoverflow.com/questions/2728292/matlab-postpones-disp-calls-when-doing-demanding-calculations-why-is-that). This is a known fact, so far so good.

But now I have a customer whose code which performs the computation is a MATLAB p-file (encrypted) so I have no access to the code to put `drawnow` there.

*Unsuccessful attempt:*

I tried spinning up a timer to do the job of calling `drawnow` but it does not seem to work - timer itself needs a precedent `drawnow` to fire its callbacks.

**EDIT:** At the end I implemented GUI with .NET/WPF running on another thread, so it remains always responsive and looks much better then original MATLAB.

Answer: 
I don't know whether this can be done properly. I've never found a way of getting the effect of drawnow in the middle of a mex file, and I would guess this situation is similar. But here is an incredibly messy hack anyway :D. If you have a p-file, you can run:

```
profile on;
pfile();
profile viewer;

```

and get an idea of what functions pfile() is calling. If the code is calling any built-in functions (e.g. disp) or any function whose source-code you have access to, you can create your own version of that file further up the path, which will be called by the p-file, e.g.

```
function disp(X)
  if (toc > 5)
    drawnow;
    tic;
  end
  builtin('disp', X);

```

This will call drawnow at most once every 5 seconds, though it won't be much use unless disp were called regularly. If you can't find a builtin to override, you could use any other function and just insert the drawnow part at the top, like:

```
function primes(N)
  if (toc > 5)
    drawnow;
    tic;
  end
  The rest of the original primes.m here.

```
Just an idea. You could build a jar file from the p-file using Matlab builder for java. 
From within Java you could do the calculation now in a separate thread.