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

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

On Thu, 2 Oct 2003 13:18:32 +0100, Mark Howard <mh...@de...> wrote:

> The next stage is to actually receive notification of the events from
> the native layer. This is done through the addEvents method. The jni
> code is done in other parts of java-gnome, so for things like Buttons
> and OptionMenus, it's just a case of adding:
> protected static void addEvents(EventMap anEvtMap) {
> 		Widget.addEvents(anEvtMap);
> 		anEvtMap.addEvent("clicked", "handleClick", ButtonEvent.Type.CLICK,=20
> ButtonListener.class);

Hi.. I took a look at some of the classes and thought they had some weird=
=20
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
     }
}

public class Button extends Bin {
     protected void initializeEventHandlers() {
	super.initializeEventHandlers();
	evtMap.initialize(this);
     }

     protected static void addEvents(EventMap evtMap) {
	Widget.addEvents(evtMap);
	// .. add button-specific events
     }
}

public class Bin extends Container {
     // no initializeEventHandlers(), so it uses the one from Container

     protected static void addEvents(EventMap evtMap) {
	Container.addEvents(evtMap);
     }
}

public class Container extends Widget {
     protected void initializeEventHandlers() {
	evtMap.initialize(this);
     }

     protected static void addEvents(EventMap evtMap) {
	Widget.addEvents(evtMap);
	// .. add container-specific events
     }
}

public class HBox extends Box {
     // no initializeEventHandlers(), so it uses the one from Container

     protected static void addEvents(EventMap evtMap) {
	Box.addEvents(evtMap);
     }
}

public class Box extends Container {
     // no initializeEventHandlers(), so it uses the one from Container

     protected static void addEvents(EventMap evtMap) {
	Container.addEvents(evtMap);
     }
}

Now first off, ToggleButton.addEvents() calls Button.addEvents() i.e. the=
=20
superclass' addEvents(). But Button.addEvents() call Widget.addEvents()=20
while its superclass is Bin. Bin again calls its superclass' addEvents(),=
=20
and so does Container. As a first impression, one would think the=20
Widget.addEvents() in the Button class should be Bin.addEvents().

On the other hand, one can see that the initializeEventHandlers() always=20
also calls initializeEventHandlers() for it's superclass. And since all=20
implementations of initializeEventHandlers() call their superclasses'=20
initializeEventHandlers(), one would think that calling for example=20
Container.addEvents() from Bin.addEvents() wouldn't be necessary.

If I understood the code correctly however, this will just result in some=
=20
signals being registered twice. I didn't have time to figure out whether=20
there are some checks to avoid duplicate registration. But anyway, becaus=
e=20
of the subclass calling the superclass, all events seem to get registered=
=20
anyway.

As far as I understood, all calls to the parent's addEvents() method coul=
d=20
be removed, since the super.initializeEventHandlers() will call the=20
initializatieEventHandlers() for its superclasses as well, eventually=20
initializing all superclasses' signals for the object in question.

Now if I got something wrong, please correct me. If you give guidelines=20
for how these really should be, I can see if I could create a patch for=20
the javas too..

Anyway I'll try to implement the OptionMenu events according to=20
ToggleButton's example and see what I can do..

- xkr47