gobject.io_add_watch continuous callback from pyalsaaudio

Question

I'm trying to create a small custom mixer that suits my needs, using python 2.7 and pyalsaaudio 0.7, but I'm stuck with events got from alsamixer when another program changes the volume values. I tried to understand how other mixers work (for example volti) and, as far as I understand, it should work as expected, but even if the method is similar, I still get a continuous loop of event response from io_add_watch. So, I suppose that I don't understand how io_add_watch works yet.

This is a small version of the code:

class MyMixer(gtk.Window):
    def __init__(self):
        super(MyMixer, self).__init__()
        self.m = alsaaudio.Mixer(control='Headphone', id=1, cardindex=0)
        """ here go the mixer widgets """
        self.show_all()
        fd, event = self.m.polldescriptors()[0]
        self.watch = gobject.io_add_watch(fd, event, self.update)


    def update(self, *args):
        print 'changed'
        """ here I update mixer widgets """
        return True

mixer = MyMixer()
gtk.main()

What am I getting wrong?

Answer 1

When you get an event from the poll descriptors, you must call snd_mixer_handle_events(). pyalsaaudio has no mechanism for that.