<?xml version="1.0" encoding="utf-8"?>
<page xmlns="http://projectmallard.org/1.0/" xmlns:its="http://www.w3.org/2005/11/its" xmlns:xi="http://www.w3.org/2001/XInclude" type="guide" style="task" id="progressbar.py" xml:lang="ca">
  <info>
    <title type="text">ProgressBar (Python)</title>
    <link type="guide" xref="beginner.py#display-widgets"/>
    <link type="next" xref="spinbutton.py"/>    
    <revision version="0.2" date="2012-06-12" status="draft"/>

    <credit type="author copyright">
      <name>Marta Maria Casetti</name>
      <email its:translate="no">mmcasetti@gmail.com</email>
      <years>2012</years>
    </credit>

    <desc>A widget which indicates progress visually.</desc>
  </info>

  <title>ProgressBar</title>
  <media type="video" mime="application/ogv" src="media/progressbar.ogv">
    <tt:tt xmlns:tt="http://www.w3.org/ns/ttml">
      <tt:body>
        <tt:div begin="0s" end="6s">
          <tt:p>
              Pressing any key stops and starts this ProgressBar.
          </tt:p>
        </tt:div>
      </tt:body>
    </tt:tt>
  </media>
  <p>This ProgressBar is stopped and started by pressing any key.</p>

  <links type="section"/>

  <section id="code">
  <title>Code used to generate this example</title>

  <code mime="text/x-python" style="numbered">from gi.repository import GLib
from gi.repository import Gtk
import sys


class MyWindow(Gtk.ApplicationWindow):
    # a window

    def __init__(self, app):
        Gtk.Window.__init__(self, title="ProgressBar Example", application=app)
        self.set_default_size(220, 20)

        # a progressbar
        self.progress_bar = Gtk.ProgressBar()
        # add the progressbar to the window
        self.add(self.progress_bar)

        # the method self.pulse is called each 100 milliseconds
        # and self.source_id is set to be the ID of the event source
        # (i.e. the bar changes position every 100 milliseconds)
        self.source_id = GLib.timeout_add(100, self.pulse)

    # event handler
    # any signal from the keyboard controls if the progressbar stops/starts
    def do_key_press_event(self, event):
        # if the progressbar has been stopped (therefore source_id == 0 - see
        # "else" below), turn it back on
        if (self.source_id == 0):
            self.source_id = GLib.timeout_add(100, self.pulse)
        # if the bar is moving, remove the source with the ID of source_id
        # from the main context (stop the bar) and set the source_id to 0
        else:
            GLib.source_remove(self.source_id)
            self.source_id = 0
        # stop the signal emission
        return True

    # source function
    # the progressbar is in "activity mode" when this method is called
    def pulse(self):
        self.progress_bar.pulse()
        # call the function again
        return True


class MyApplication(Gtk.Application):

    def __init__(self):
        Gtk.Application.__init__(self)

    def do_activate(self):
        win = MyWindow(self)
        win.show_all()

    def do_startup(self):
        Gtk.Application.do_startup(self)

app = MyApplication()
exit_status = app.run(sys.argv)
sys.exit(exit_status)
</code>

  </section>

  <section id="methods">
  <title>Useful methods for a ProgressBar widget</title>
  <list>
    <item><p>Instead of <code>pulse()</code>, that makes the bar go back and forth, if we want the ProgressBar to "fill in" a fraction (a <code>float</code> between <code>0.0</code> and <code>1.0</code> included) of the bar that has been completed, use <code>set_fraction(fraction)</code>.</p></item>
    <item><p>To set a text and show it (superimposed over the bar) use <code>set_text(<var>"text"</var>)</code> and <code>set_show_text(True)</code>. If a text is not set and <code>set_show_text(True)</code> the text will be the percentage of the work that has been completed.</p></item>
  </list>
  </section>

  <section id="references">
  <title>API References</title>
  <p>In this sample we used the following:</p>
  <list>
    <item><p><link href="http://developer.gnome.org/gtk3/unstable/GtkProgressBar.html">GtkProgressBar</link></p></item>
    <item><p><link href="http://developer.gnome.org/glib/stable/glib-The-Main-Event-Loop.html">GLib - The Main Event Loop</link></p></item>
    <item><p><link href="http://developer.gnome.org/gdk/stable/gdk-Keyboard-Handling">Gdk - Key Values</link></p></item>
  </list>
  </section>
</page>
