Optimized torrentview.cell_data_trackericon

cell_data_trackericon would load the tracker icon with
gtk.gdk.pixbuf_new_from_file_at_size each time it's requested.
These regular requests acumulating to thousands calls to
pixbuf_new_from_file_at_size with a big torrent list.

Now, read the tracker icon from disk once, and cache it.

deluge/ui/gtkui/torrentview.py

@@ -116,24 +116,29 @@ def cell_data_statusicon(column, cell, model, row, data):
 
 def cell_data_trackericon(column, cell, model, row, data):
     def on_get_icon(icon):
-        def create_blank_icon():
+        def create_blank_pixbuf():
             i = gtk.gdk.Pixbuf(gtk.gdk.COLORSPACE_RGB, True, 8, 16, 16)
             i.fill(0x00000000)
             return i
 
         if icon:
-            try:
-                icon = gtk.gdk.pixbuf_new_from_file_at_size(icon.get_filename(), 16, 16)
-            except Exception, e:
-                icon = create_blank_icon()
+            pixbuf = icon.get_cached_icon()
+            if not pixbuf:
+                try:
+                    pixbuf = gtk.gdk.pixbuf_new_from_file_at_size(icon.get_filename(), 16, 16)
+                except gobject.GError, e:
+                    # Failed to load the pixbuf (Bad image file), so set a blank pixbuf
+                    pixbuf = create_blank_pixbuf()
+                finally:
+                    icon.set_cached_icon(pixbuf)
         else:
-            icon = create_blank_icon()
+            pixbuf = create_blank_pixbuf()
 
         #Supress Warning: g_object_set_qdata: assertion `G_IS_OBJECT (object)' failed
         with warnings.catch_warnings():
             warnings.simplefilter("ignore")
-            if cell.get_property("pixbuf") != icon:
-                cell.set_property("pixbuf", icon)
+            if cell.get_property("pixbuf") != pixbuf:
+                cell.set_property("pixbuf", pixbuf)
 
     host = model[row][data]
     if host:

deluge/ui/tracker_icons.py

@@ -74,6 +74,7 @@ class TrackerIcon(object):
         self.filename = os.path.abspath(filename)
         self.mimetype = extension_to_mimetype(self.filename.rpartition('.')[2])
         self.data = None
+        self.icon_cache = None
 
     def __eq__(self, other):
         """
@@ -122,6 +123,20 @@ class TrackerIcon(object):
         """
         return self.filename if full else os.path.basename(self.filename)
 
+    def set_cached_icon(self, data):
+        """
+        Set the cached icon data.
+
+        """
+        self.icon_cache = data
+
+    def get_cached_icon(self):
+        """
+        Returns the cached icon data.
+
+        """
+        return self.icon_cache
+
 class TrackerIcons(Component):
     """
     A TrackerIcon factory class