A little program to show how a gtk gui gets unresponsive when using gtk2reactor and downloading a file with twisted.web.client.HTTPDownloader.

gui_slowdown.py

"""
A little program to show how a gtk gui gets unresponsive when using
gtk2reactor and downloading a file with twisted.web.client.HTTPDownloader.

Enter the url (HTTP) of a large file into the textbox and press start.
The progress bar becomes visibly jerky, while I'd expect that it stays
smooth.  Apparently twisted doesn't return control to GTK fast enough.

To set up a mini web server, you can use:
    
    $ twistd -n web --path /path/to/large/file

"""

from urlparse import urlparse
import gtk, gobject

from twisted.internet import gtk2reactor
gtk2reactor.install()

from twisted.internet import reactor, defer
import twisted.web.client as twc


class MainWindow(gtk.Window):
    def __init__(self):
        gtk.Window.__init__(self)
        self.set_default_size(300, 150)

        vb = gtk.VBox(spacing=6)
        self.add(vb)

        self.enURL = gtk.Entry()
        self.enURL.set_text("http://localhost:8080/video.avi")
        vb.pack_start(self.enURL, False, True)

        self.lblStatus = gtk.Label("Press Start")
        vb.pack_start(self.lblStatus, False, True)

        self.bbButtons = gtk.HButtonBox()
        vb.pack_start(self.bbButtons, False, True)
        self.btnStart = gtk.Button("Start")
        self.btnStart.connect("clicked", self.btnStart_clicked)
        self.bbButtons.pack_start(self.btnStart)

        self.pbDemo = gtk.ProgressBar()
        self.pbDemo.set_text("Testing smoothness")
        vb.pack_start(self.pbDemo, False, True)

        vb.pack_start(gtk.HBox(), True, False)
        vb.pack_start(gtk.Statusbar(), False, True)

        gobject.timeout_add(50, self.update_spinner, [0])

        vb.show_all()

    @defer.inlineCallbacks
    def btnStart_clicked(self, widget):
        url = self.enURL.get_text()
        scheme, host, port, path = twc._parse(url)
        filename = path.rpartition("/")[2]
        outfile = filename
        print url, "->", outfile
        factory = twc.HTTPDownloader(url, outfile)
        
        self.btnStart.set_sensitive(False)
        self.enURL.set_sensitive(False)
        self.lblStatus.set_text("Downloading...")

        print host, port
        self.connector = reactor.connectTCP(host, port, factory)

        result = yield factory.deferred
        print "finished"
        print result

        self.btnStart.set_sensitive(True)
        self.enURL.set_sensitive(True)
        self.lblStatus.set_text("Done!")

    def update_spinner(self, status):
        old = status[0]
        new = old + 2
        if new > 100:
            new = 0
        self.pbDemo.set_fraction(float(new)/100.)
        status[0] = new
        return True


def main():
    win = MainWindow()
    win.show_all()
    reactor.run()


if __name__ == "__main__":
    main()