Need Help Regarding multithreading in gtkmm

Question

I am not very bad with threading, i need help,

I have a gtkmm window with progress bar, task is to execute multiple shell scripts or shell commands in background and update the progress bar accordingly. i have a

button->clicked_signal() {
         thread( [this] { worker->start() } ); 
}  


worker->start() {
      {
         lock_guard(mutex);         // as per i know to safely handle variables 
         progress = 0.0      
     }
      caller->notify();             // i found it on documentation that its for sending signal to window to refresh

   int ret = WEXITSTATUS(system("./my_shell_script with-args"));
  {
     lock_guard(mutex);
     progress = 0.4;
   }
  caller->notify();       // Simmilary i am handling more scripts
} 

Issue is that Complete window is freezing until the process finish. its only happening for system(); , if i use for loop() or other function then it will not freeze.

I tried other thing.

worker->executor() {
      int ret = WEXITSTATUS(system("./my_shell_script with-args"));
      {
         lock_guard(mutex);
         progress = 0.4;
       }
        // other executions
 }

worker->start() {
      thread  th1(&worker::executor, this);
      while(true) {
          caller->notify();
          if (stop) break;                             

      this_thread::sleep_for(chrono::milliseconds(120));     
      }

     th1.join();
     caller->notify();
} 

But Still Freezing. I am very bad at threading,

complete codes are available at https://github.com/itsManjeet/opportunity.git BRANCH (0.6.0)

Is their any better way to do this thing

Answer 1

You cannot make any GUI changes or use any other GTK functions from any thread except the main one. If you need to change a progress bar, for example, then you have to signal the main thread to do it, instead of trying to make the change from the worker thread. You can use Glib::Dispatcher for this.