Re: [Java-gnome-developer] OptionMenu events etc..

[Jonas B. <jb...@ni...>]

On Fri, 03 Oct 2003 23:47:19 +0300, Jonas Berlin <jb...@ni...>=
=20
wrote:

> Hi.. I took a look at some of the classes and thought they had some=20
> weird initialization style:
>
> public class ToggleButton extends Button {
>      protected void initializeEventHandlers() {
> 	super.initializeEventHandlers();
> 	evtMap.initialize(this);
>      }
>
>      protected static void addEvents(EventMap evtMap) {
> 	Button.addEvents(evtMap);
> 	// .. add togglebutton-specific events
>      }
> }

I did some research, a bunch debug prints in the signal-related codes to=20
test & verify the behaviour.

I found out that my previous statements were at least partially correct.

The situation is like this:
  1. initializeEventHandlers() methods call super.initializeEventHandlers=
()=20
(except for some cases)
  2. most addEvents() methods call addEvents() of some superclass, usuall=
y=20
<superclass>.addEvents() or then Widget.addEvents.

The result from this duplicate behaviour is that some event handlers get=20
registered multiple times. One easy way to test this is to do:

   LifeCycleListener lcl =3D new LifeCycleListener() {
       public void lifeCycleEvent(LifeCycleEvent evt) {
         System.out.println(evt);
       }
     };

   Button b =3D new Button("foo");
   b.addListener(lcl);
   b.show();

This will display something like:

org.gnu.gtk.event.LifeCycleEvent[source=3Dorg.gnu.gtk.Button@18a992f,id=3D=
SHOW]
org.gnu.gtk.event.LifeCycleEvent[source=3Dorg.gnu.gtk.Button@18a992f,id=3D=
SHOW]

Now if you change Button to ToggleButton, it instead shows:

org.gnu.gtk.event.LifeCycleEvent[source=3Dorg.gnu.gtk.ToggleButton@f72617=
,id=3DSHOW]
org.gnu.gtk.event.LifeCycleEvent[source=3Dorg.gnu.gtk.ToggleButton@f72617=
,id=3DSHOW]
org.gnu.gtk.event.LifeCycleEvent[source=3Dorg.gnu.gtk.ToggleButton@f72617=
,id=3DSHOW]

-----------

Now I suggest the following:

1. make sure all initializeEventHandlers() call=20
super.initializeEventHandlers(), with the only exception being Widget,=20
which is the topmost widget class.
2. remove all <anywidgetclass>.addEvents() calls from the addEvents()=20
methods of the various classes.

This way, events should be registered only once, and as a bonus, the code=
=20
will most likely be easier to read also =3D)

I'll start working on a patch that will fix all widget classes according=20
to my suggestion. If you have some better solution for this then I can tr=
y=20
that as well :)

- xkr47