Auto-convert gtk.Button from .ui files (Touch UI)

Convert all gtk.Button widgets loaded from .ui files to
finger-friendly widget if enable_fingerscroll is True.

src/gpodder/gtkui/base.py

@@ -162,6 +162,9 @@ class GtkBuilderWidget(object):
     def _handle_menu_bar(self, menu):
         pass
 
+    def _handle_button(self, button):
+        pass
+
     def set_attributes(self):
         """
         Convert widget names to attributes of this object.
@@ -180,6 +183,9 @@ class GtkBuilderWidget(object):
             if isinstance(widget, gtk.MenuBar):
                 self._handle_menu_bar(widget)
 
+            if isinstance(widget, gtk.Button):
+                self._handle_button(widget)
+
             # The following call looks ugly, but see Gnome bug 591085
             widget_name = gtk.Buildable.get_name(widget)
 

src/gpodder/gtkui/interface/common.py

@@ -105,6 +105,10 @@ class BuilderWidget(GtkBuilderWidget):
         for child in menu_bar.get_children():
             self.set_finger_friendly(child)
 
+
+    def _handle_button(self, button):
+        self.set_finger_friendly(button)
+
     def on_window_orientation_changed(self, orientation):
         """Override this method to relayout a window for portrait mode."""
         pass