threads with gtk gui problem

[Andy Baxter]

Hi,

I'm working on adding a Gtk GUI to a python program. Its main function 
is to read raw data from an arduino board over USB, and convert it to 
MIDI note/controller events to be sent to another program. I've had it 
working fine with just a command line interface, but when I replaced the 
command line with a Gtk interface, I started having problems getting the 
thread that reads the USB port to run.

I'm not sure what the custom is on this list for pasting code - It's a 
long program so I don't want to paste the whole thing.

The sequence of events I've coded is:

- the program starts.
- the port reader thread (which is a threading.Thread subclass) is 
initialised.
- the object which controls the interface is initialised (i.e. the glade 
file is loaded.)
- the port reader is started (i.e. the 'start' method is called, which 
calls the 'run' method in a thread).
- then the gtk main loop is run.

The behaviour I'm getting is that the port reader either fails to start, 
or stops running at the point where it tries to initialise the serial 
port. It then does nothing until I close the main window, at which point 
it starts running again.

The port reader's run method begins like this:

    # the method called by the thread superclass to run the main loop of 
the thread.
    def run(self):
       # main loop of thread.
       print "Starting port reader."
       fhan=serial.Serial(port=keeper.config['usbPort'], 
baudrate=keeper.config['usbBaud'], timeout=0.1)
       print "1"
       fhan.open()
       print "2"
       seq=PySeq() # the sequencer library object
       port=seq.createOutPort(keeper.config['midiPortName']) # make a 
midi out port.
       midich=keeper.config['midich']
       print "3"
       while True:
          inbuf=[]
          print ".",
          char=fhan.read(1)
          if self.quit:
             fhan.close()
             return
          if len(char)==0: continue
          ... (code to process the character read in)

('keeper' is a global object which stores the config data and references 
to a few key objects).

When you start the program, the thread stops either before the first 
print statement, or on the line which initialises the serial port ( 
fhan=serial.Serial(...) ). '1', '2', and '3' only get printed /after/ 
you close the gtk main window.

Can anyone help with this?

cheers,

andy baxter



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