How do I update/redraw a GTK Widget (GTKLabel) int

Question

I have some code below that is attempting to update a GTK Label element. I'm including two files: the ui file and the py file.

UI file:

<glade-interface>
  <widget class="GtkWindow" id="ApplicationFrame">
    <property name="width_request">320</property>
    <property name="height_request">240</property>
    <property name="visible">True</property>
    <property name="events">GDK_KEY_PRESS_MASK</property>
    <property name="title" translatable="yes">Simple</property>
    <property name="resizable">False</property>
    <property name="window_position">center-always</property>
    <property name="default_width">320</property>
    <property name="default_height">240</property>
    <property name="decorated">False</property>
    <property name="gravity">center</property>
    <child>
      <widget class="GtkFixed" id="layout">
        <property name="width_request">320</property>
        <property name="height_request">240</property>
        <property name="visible">True</property>
        <child>
          <widget class="GtkLabel" id="l1">
            <property name="width_request">320</property>
            <property name="height_request">40</property>
            <property name="visible">True</property>
            <property name="xalign">0</property>
            <property name="label" translatable="yes">l1</property>
          </widget>
          <packing>
            <property name="y">43</property>
          </packing>
        </child>
      </widget>
    </child>
  </widget>
</glade-interface>

Python File

import os
from time import sleep as wait
import gtk as gtk
import gtk.glade as glade
import gobject

class Application(object):
    def __init__ (self):
        self.glade = glade.XML("simple.ui")
        self.setup_ui()

    def setup_ui (self):
        self.window = self.glade.get_widget("ApplicationFrame")
        self.l1 = self.glade.get_widget("l1")
        self.names = {'l1' : self.l1}
        self.all = [self.l1]
        gobject.timeout_add(1000,self.display_me)
        gobject.timeout_add(100,self.do_something_that_takes_a_while)
        self.window.add_events(gtk.gdk.KEY_PRESS_MASK)
        self.window.connect("key-press-event", self.handler)
        self.window.connect("delete_event", self.delete_event)
        self.window.connect("destroy", self.destroy)
        self.window.show()

    def get_signal (self,widget,event):
        keyname = gtk.gdk.keyval_name(event.keyval)
        ctrl = event.state & gtk.gdk.CONTROL_MASK
        alt = event.state & gtk.gdk.MOD1_MASK
        shift = event.state & gtk.gdk.SHIFT_MASK
        name = []
        if ctrl and keyname not in ["Control_L","Control_R"]: 
            name.append("CTRL")
        if alt and keyname not in ["Alt_L","Alt_R"]:
            name.append("ALT")
        if shift and keyname not in ["Shift_L","Shift_R"]:
            name.append("SHIFT")
        name.append(keyname)
        name = "+".join(name)
        return name

    def handler (self,widget,event):
        name = self.get_signal(widget,event)
        if name.lower() in ['ctrl+x','ctrl+c','alt+q']:
            self.destroy()

    def main(self):
        gtk.main()

    def delete_event (self,widget=None,event=None,data=None):
        return False

    def destroy (self,widget=None,data=None):
        gtk.main_quit()

    def get (self,item):
        if isinstance(item, str): 
            if item in self.names:
                item = self.names[item]
        retval = None
        if hasattr(item,"text"):
            retval = item.text()
        elif hasattr(item,"get_label"):
            retval = item.get_label()
        return retval

    def set (self,item,text='',font=None):
        print 'Setting...'
        if isinstance(item, str): 
            if item in self.names:
                item = self.names[item]
        retval = None
        if font == None and hasattr(self,"page") and hasattr(self.page,"NORMAL_FONT"): 
                font = self.page.NORMAL_FONT
        if hasattr(item,"setText"):
            retval = item.setText(text)
        elif font == None:
            if hasattr(item,'set_text'):
                retval = item.set_text(text)
        elif hasattr(item,"set_label"):
            retval = item.set_label(text)
            if hasattr(item,"modify_font") and font != None:
                item.modify_font(font)
        item.queue_draw()
        self.try_to_update(item)
        print 'done'
        return retval

    def try_to_update (self,item):
        """
        do something here to update the visual screen????
        """
        print str(self)

    def do_something_that_takes_a_while (self):
        timeout = 15
        while timeout != 0:
            self.set('l1','%s' % timeout)
            wait(1)
            timeout -= 1
            print timeout
        return 1

    def clean (self):
        if item != None:
            self.set(item,empty_text)
        else:
            if hasattr(self,'all'):
                for item in self.all:
                    self.set(item)

    def display_me (self):
        print str(self)
        return True

    def __str__ (self):
        space = 25
        value = '%'+str(space)+'s'
        lines = ['\n','-'*79]
        if hasattr(self,'all'):
            line = []
            for obj in self.all:
                obj_value = self.get(obj)
                line.append(value % obj_value if obj_value != None else '')
                #line.append(value % ' ')
            lines.append(''.join(line))
        lines.append('-'*79)
        return '\n'.join(lines)


if __name__ == "__main__":
    from time import sleep as wait
    SEC = 1
    app = Application()
    app.main()

This should be simple, but I'm completely missing what I'm doing wrong. The element, l1, is not getting updated properly. I think the code within try_to_update is where I need to update the UI, but I'm at a loss as to which function I need to call. Can someone please help?

Thanks in advance!

Answer 1

You'll want to use the Widget's queue_draw function:

The queue_draw_area() method invalidates the rectangular area of the widget (...) by calling the gtk.gdk.Window.invalidate_rect() method on the widget's window and all its child windows.

But, as you are already doing that in your set method, my guess is that the

if hasattr(item,'show')

check prevents the item from updating. Another check is to call the queue_draw function on the entire window, and see if that updates things.

Alternatively, force the events that are queued to be processed as follows:

while gtk.events_pending():
    gtk.main_iteration_do(True)

Answer 2

One thing that happens in the code is that while do_something_that_takes_a_while is executed, no events are being processed. One way to solve that is to force event processing at some point inside that method:

--- code.py 2011-12-05 10:32:53.000000000 +0100
+++ code.py.bak 2011-12-05 10:27:22.000000000 +0100
@@ -95,8 +95,6 @@
         timeout = 15
         while timeout != 0:
             self.set('l1','%s' % timeout)
-            while gtk.events_pending():
-                gtk.main_iteration()
             wait(1)
             timeout -= 1
             print timeout