c - GTK3 and multithreading, replacing deprecated functions

Question

I would like to replace deprecated functions gdk_threads_enter()/leave() in my application that uses threads. The application as it is now, works perfect (although i am not sure if this is the right way to do it).

My main loop, runs the gtk_main and the signal handlers. When i receive a start button, i start a thread, that runs in the background along the main. How can i update the GUI from that thread. I know per the Documentation of GTK3 and GDK3, they say avoid it by using

gdk_threads_add_idle() 

or

gdk_threads_add_timeout() 

But how do I do this if I want the updating to be done only when I click start? is there any example. I am not asking how to use gdk_threads_add_idle(), I am asking how to run worker function in the main without a thread after clicking start.

Button clicked --> start the worker function "in thread previously" --> update large amount of GUI elements in the GUI window.

Answer 1

What the documentation says is that you can still run your worker function in a thread, you just can't use GTK and GDK functions from that thread. So, you can still start the thread when you click start. But instead of updating GUI elements from the thread, you have to schedule them to be updated from the main thread by using gdk_threads_add_idle().

So your diagram should look something like this:

Main thread     Worker thread
    |
Button clicked
    |      \________
    |               
    |           Start worker function
    |                |
    |           Computation
    |                |
    |           Want to update GUI
    |                |
    |           gdk_threads_add_idle(function1, data1)
    | ______________/|
    |/               |
    v           More computation
function1 runs       |
    |           Want to update GUI
GUI updated          |
    |           gdk_threads_add_idle(function2, data2)
    | ______________/|
    |/               |
    v           More computation
function2 runs       |
    |      
  etc...

If this is too complicated for your use case, and you have a computation in your worker thread that returns control to your worker thread often enough (say, you are calculating something in a loop), then you can run the calculation entirely in the main thread without locking up the GUI by briefly returning control to the GUI main loop, like so:

for (lots of items) {
    result = do_short_calculation_on(one_item);

    update_gui(result);

    while (gtk_events_pending())
        gtk_main_iteration();
}