Question

How do you refresh the tk gui while doing some computation inside of a button call back routine?

The routine takes a long time, and the user wants to see some progress.

Need some way to repaint the screen / look for the cancel button.

in gtk its like this:

/* computation going on */
...
    while (gtk_events_pending ())
      gtk_main_iteration ();
...
/* computation continued */

Answer 1

I might be missing the point, but why would’t you use thread for that? You won’t be able to join it in a callback, but you still should be able to generate an event.

TkButton.new :text => 'Hard routine',
             :command => proc { Thread.new { hard_routine } }.pack
Tk.mainloop

doing the heavy things in your callback is considered a bad practice since it blocks the entire event loop so your gui freezes.