On Thu, Jul 11, 2013 at 4:30 PM, Nick Pratt <[email protected]> wrote:
> I think this is great - we have some tables now with a ton of JS events on
> the child elements. Just to clarify, will this make the rendered page
> smaller since there will only be a single JS handler for the event for the
> container rather than N JS handlers?
>
At the moment all attributes for an inner element are preserved.
'e' (the event name), 'c' (the component markup id), pd (prevent default),
sp (stop propagation) can be removed because they are not really used.
But every inner element can have its own call listeners, form submitters
can also have custom settings ('f', 'sc', 'mp', 'm'), so I think they have
to be preserved.
If you look in #updateAjaxAttributes() for your ajax behaviors in your
table cells you will probably notice that they have their own attributes.
>
> Making it switchable (I think how Sven suggested) would be an improvement -
> we could leave it off by default, but provide a simple switch on a
> per-container (or per-app) basis that would allow the dev to choose.
>
Yes, it looks as an improvement.
Moving the current code to such implementation is easy.
The idea with plain JS solution I cannot visualize in my head yet.
>
> Regards
>
> Nick
>
> On Thu, Jul 11, 2013 at 4:59 AM, Martin Grigorov <[email protected]
> >wrote:
>
> > Hi,
> >
> > At https://github.com/apache/wicket/compare/event-delegating-behavioryou
> > may see the diff between master and event-delegating-behavior branches.
> >
> > The latter provides a new AjaxEventBehavior (AEB) -
> EventDelegatingBehavior
> > (EDB), that suppresses the JS event binding for all AjaxEventBehaviors
> for
> > a given event type (click, submit, change, ...) in the children
> components
> > of the host component of EDB.
> >
> > How EDB works:
> >
> > - until now AjaxEventBehavior#renderHead() renders ondomready header item
> > with JS snippet like:
> > Wicket.Ajax.ajax(attributesObject);
> > In the new branch there is a check if some parent has EDB for the event
> > type of this AEB, and if there is such then the AEB "donates" its
> > attributes to the EDB.
> >
> > - EventDelegatingBehavior#getCallbackScript() renders :
> > Wicket.Event.delegate('edbComponentMarkupId', 'eventType', edbAttributes,
> > childrenAttrsMap);
> >
> > - when a delegated component fires its event (e.g. the user clicks on an
> > AjaxLink) the event is handled by EDB's event handler. It extracts the
> > markupId of the inner HTML element and fires Wicket.Ajax.Call with the
> > specific attributes for the extracted inner element.
> >
> > Pros:
> >
> > - simple to use - just add EDB to a container component around your Ajax
> > heavy component (e.g. repeater with many Ajax behaviors). See the demo
> app
> > at https://issues.apache.org/jira/browse/WICKET-5267
> >
> > - faster JS execution
> > -- faster execution of the domready handler because there is just one
> > binding instead of N
> > -- faster reaction because the browser finds the event handler much
> faster.
> > I wasn't able to prove this with numbers because there is no way to
> detect
> > the 'start time', i.e. when the user makes the action. With JS the
> earliest
> > point is when the browser has already looked up the event handler.
> > Chrome Dev tools (timeline, profiling, pagespeed) don't help too. So my
> > reference that it is faster are the articles in the web and a use case in
> > our application.
> >
> > Cons:
> >
> > - AEB#renderHead() needs to check whether there is EDB up in the
> hierarchy
> > to be able to decide what to do.
> > This is ugly, I agree. But I see no other solution that will preserve the
> > transparent usage of something like EDB and will not require a major
> > rewrite of user applications to be able to use event delegation.
> > -- there are some optimizations to lower the impact of the new checks:
> > --- a new setting (IAjaxSettings#useEventDelegation) - a global property
> > that prevents visiting the parent components and their behaviors for all
> > apps which do not use EDB
> > --- when EDB is bound it registers a metadata for its event type in the
> > page instance. This prevents visiting all behaviors of all parent
> > components
> >
> >
> > I have no more ideas how to further optimize it.
> >
> > Any feedback is welcome! Even if you have a completely different idea how
> > to implement this functionality.
> >
> > Thanks for reading!
> >
>
