GTK+ Forums

Warp · Familiar Face Joined: 24 Feb 2007 Posts: 13

I want to create a GUI for a program which performs lengthy calculations. Its current command-line version prints from time to time a percentage indicating the progress of the calculations. I would like the GUI version to show a progress bar (or anything similar) for this same purpose. However, this doesn't seem to be as simple as it sounds at first. AFAIK there would be two options for this:

1) Have the program "refresh" the application window from time to time, using the current progress value. I actually don't know how to do this (or if it's at all possible with GTK+). If I'm not mistaken, by default GTK+ can refresh the application window only when it gets control. As long as some function is doing calculations (basically in a busy loop) GTK has no control and thus the window does not get refreshed in any way.

2) Use multithreading: The main GUI application (and thus GTK) runs in one thread and the calculation routine in another. The GUI thread reads from time to time the progress of the calculation thread and updates the window accordingly.

Either option would be fine, although option 2 would obviously be much better: The application window would be more responsive and it would be easy to implement extra GUI features such as a button to cancel the calculations. However, since I don't have too much experience about creating threads I'm not completely sure how this should be done. And is GTK+ thread-safe?

How should I do this?

I'm using linux and GTK+ 2.6.4.

openldev · Posted: Fri Jun 15, 2007 9:00 pm Post subject:

With GTK+, you should only ever have one thread touching the GUI at a time. If not, you can run into terrible problems.

One option would be to use a timeout, which would call a function every second or two to update the progress bar.

Warp · Familiar Face Joined: 24 Feb 2007 Posts: 13

openldev · Posted: Sun Jun 17, 2007 12:55 pm Post subject:

Check out the sections on:

Threads: http://developer.gnome.org/doc/API/2.0/glib/glib-Threads.html
Thread Pools: http://developer.gnome.org/doc/API/2.0/glib/glib-Thread-Pools.html
Asynchronous Queues: http://developer.gnome.org/doc/API/2.0/glib/glib-Asynchronous-Queues.html

bobyjoe · Joined: 24 Jun 2007 Posts: 1

openldev · Posted: Sun Jun 24, 2007 12:24 am Post subject:

When you create a timeout, you can set the priority. If tasks with a higher priority are pending, the timeout will not be called. So, you should set it high enough to force it to run.

Warp · Familiar Face Joined: 24 Feb 2007 Posts: 13

It was quite simple, after all:

1) At the beginning of main(), call g_thread_init(NULL);
2) When I want to launch the calculation thread, I call g_thread_create().
3) After launching that thread, set a timer for calling the progress bar update with gtk_timeout_add()
4) Inside that progress bar updating function, if the calculation thread is still running, make the same gtk_timeout_add() again.