I have been working on a Pygtk pgrogram for the OLPC project which is a
reading program for Project Gutenberg Etexts. Several people on the
OLPC mailing list suggested enhancing it to work with speech-dispatcher
so that the program could read the texts aloud, at the same time
highlighting the word as it is spoken. They felt it would be useful to
students trying to improve their reading skills, etc. What I have found
is that getting the program to read aloud is easy, getting a Pygtk
program to highlight words one a a time is easy, but getting the two to
work together might be impossible.
Speech-dispatcher runs in its own thread. It has callbacks that I have
configured to execute a Python method every time a word ends. Using
this it *should* be trivial to highlight the word as it is spoken.
Trouble is, when the Pygtk event loop is allowed to run at the same time
as speech-dispatcher, none of the callbacks are ever invoked. If I do a
wait loop after invoking speech-dispatcher, then all of the callbacks
work but the screen does not get updated to show the words being
highlighted. Only the final word on the page gets highlighted. Hynek
Hanke of the speech-dispatcher project has noticed that socket.recv()
does not work in speech-dispatcher if it is allowed to run at the same
time as the event loop.
I can supply code to demonstrate this problem. I am hoping that one of
you can suggest a good workaround.
Thanks,
James Simmons
Hynek Hanke wrote:
Hello James,
it is an interesting problem. I think pygtk needs to be fixed if it
seems to behave so badly with other libraries using threads.
This has little to do with speech callbacks specifically. More
important is the thing that when you run basic system functions
like socket.recv() from other threads, they behave badly.
Would you like to raise this issue with the PyGTK developers
to see if it is possible to fix it or to use PyGTK in some other
way that avoids the conflict?
As a workaround, you can try to avoid the pygtk loop and do
your own asynchronous thread to highlight the words. Threads
are easy in Python. However, unless we find out where in
PyGTK the problem lies exactly, it is always possible, that you will
run into the very same problems and they will prevent your
thread to work correctly.
Anyway, old or new implementation of speechd, threads will
always be used in the python communication library, since they
are technically necessary to handle asynchronous callbacks.
So it would be very useful to try to find a solution with pygtk.
With regards,
Hynek Hanke
_______________________________________________
pygtk mailing list pygtk@daa.com.au
http://www.daa.com.au/mailman/listinfo/pygtk
Read the PyGTK FAQ: http://www.async.com.br/faq/pygtk/
