Hello,
I have a certain device which sends messages via UDP. These messages
have effect on the stage rendering, which means I need to get them
periodically. The question is, what's the best way to do this? The
callback should be triggered between every redraw, i.e. there should
be no two stage redraws without the callback being called between the
redraws. Also, if the callback triggers a redraw, it shouldn't be
called again until the redraw happened. If the callback doesn't
trigger a redraw, it should be called again "very soon" (= n times per
second) to check for messages again.
Currently I am using gobject.timeout_add. This usually works okay, but
it has side effects which I don't want. Consider the code below. The
texture's position is never updated on my machine. If I uncomment
"time.sleep", everything is fine. I considered using gobject.idle_add
as well (uncommented below). This also doesn't give me the desired
effect: The texture is not drawn at all. Another thing I tried is to
connect after the stage is painted (also uncommented below). This
doesn't work either. The stage is painted a few times and the callback
is never called again.
I am now thinking about not using clutter_main, but a custom loop
which calls my callback after every gobject.MainContext.iteration().
But before I take it that far, I'd like to hear your opinions.
Thanks,
Thomas
import clutter
import gobject
import time
# Assume 20 frames per second.
def timeout_cb(stage=None):
global texture
# Here I would actually check the messages.
# To illustrate the problem, let's just move the actor by one pixel.
x, y = texture.get_positionu()
print 'updating', x
x += 1
texture.set_positionu(x, y)
# Sometimes this function can be slow. In that case redraws are blocked.
time.sleep(0.05)
return True
stage = clutter.Stage()
stage.set_size(640, 480)
stage.connect('key-press-event', clutter.main_quit)
texture = clutter.Texture()
texture.set_from_file("mypic.png")
stage.add(texture)
# Set up a callback which updates the stage periodically.
gobject.timeout_add(50., timeout_cb)
# gobject.idle_add(timeout_cb)
# stage.connect_after('paint', timeout_cb)
stage.show_all()
clutter.main()
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