On 22 sep, 22:02, "Emily Crutcher" <[EMAIL PROTECTED]> wrote:
> A more complete implementation of the event handlers has been added to
> the gwt-incubator
> gen2.event
> package<http://code.google.com/p/google-web-toolkit-incubator/source/browse/#...>.
Implementation-detail note: why is DomEvent using getTypeInt()? Why
not using getType()? It would save some string-to-int "translation"
code (see issue 2927), and given that the value is only used as a key
within DomEvent.WrappedKeyMap, I can't see a drawback (on the
contrary: adding support for other "dom events" –e.g. drag'n'drop, cut/
copy/paste, text selection, etc.– could then be done without the need
to rewrite/overwrite this string-to-int mapping). Of course, the
string-to-int mapping is still necessary for sinkEvents
(addHandlerAndSink) to work, but it would be done at registration-time
only, and not for every fired event!
This means however, that DomEvent.Key has to keep track of both the
int *and* the string event type (shouldn't this be somehow optimized
by the JSStringInterner?), and that DomEvent-derived classes thus have
to be kept "synchronized" with the getTypeInt()/sinkEvents() code (not
a big deal, this is an almost-never-changing code).
...but there are some events that have different names (mousewheel/
DOMMouseScroll). DomEvent.Key could have a register() abstract method
(with register(String name) helper method), or variations along this
line (e.g. constructor accepting an additional "String eventName" and
calling register(eventName), for the common case, and ScrollEvent
defining its own instance initializer code to call register() once
more with the second name):
public abstract static class Key<EventType extends DomEvent,
HandlerType extends EventHandler>
extends AbstractEvent.Key<EventType, HandlerType> {
int nativeEventType;
/**
* Creates a [EMAIL PROTECTED] Key}. Each event should have a singleton key.
*/
public Key(int nativeEventType) {
this.nativeEventType = nativeEventType;
register();
}
protected final void register(String eventName) {
registered.put(eventName, this);
}
protected abstract void register();
...
public static final Key<ScrollEvent, ScrollHandler> KEY = new new
Key<ScrollEvent, ScrollHandler>(
Event.ONSCROLL) {
protected void register() {
register("mousewheel");
register("DOMMouseScroll");
}
@Override
protected void fire(ScrollHandler handler, ScrollEvent event) {
handler.onScroll(event);
}
@Override
public ScrollEvent wrap(Event nativeEvent) {
return new ScrollEvent(nativeEvent);
}
};
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