[jira] Commented: (WICKET-2739) Throttling breaks AjaxFormSubmitBehavior's precondition check

["Michael Brinkman (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/WICKET-2739?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12898668#action_12898668 ] 

Michael Brinkman commented on WICKET-2739:
------------------------------------------

Interestingly, I'm seeing this issue manifest as a precondition failure running Wicket 1.4.9 on IE8, but not on FF3.6.8 (opposite browser compatibility issue).  In the IE JS debugger I tracked it back to the same basic root cause where the element passed in to 'Wicket.&&' is clearly not the form component the behavior was added to.

The only thing I'll add to Russell's description of the issue and suggested fix is that I was able to work around this by altering the precondition script to be entirely name based, instead of using a reference to a DOM element:

			AjaxFormValidatingBehavior behavior = new AjaxFormValidatingBehavior(myForm, "onblur") {
				protected CharSequence getPreconditionScript()
				{
					return "return Wicket.$$('" + ((FormComponent<?>)getComponent()).getInputName() + "')&&Wicket.$$('" + getForm().getMarkupId() + "')";
				}
			};

I'm still pretty new to Wicket though, so I'm not sure if the form validating behavior is intended to be added to anything other than a FormComponent.  If it is, then obviously this wouldn't be a very desirable fix.

> Throttling breaks AjaxFormSubmitBehavior's precondition check
> -------------------------------------------------------------
>
>                 Key: WICKET-2739
>                 URL: https://issues.apache.org/jira/browse/WICKET-2739
>             Project: Wicket
>          Issue Type: Bug
>          Components: wicket
>    Affects Versions: 1.4.5
>         Environment: wicket 1.4.5, wicket quickstart, windows XP; FireFox 3.5.7 used in quickstart test
>            Reporter: Russell Morrisey
>         Attachments: throttleBreaksPrecondition.zip
>
>
> AjaxFormSubmitBehavior#getPreconditionScript() looks like:
> return "return Wicket.$$(this)&&Wicket.$$('" + getForm().getMarkupId() + "')";
> The javascript keyword 'this' should point to the DOM element which initiated the ajax event. (It wants to check that the component still exists on the page, before initiating the ajax request, as well as the form this behavior is linked to). When using an AjaxThrottlingCallDecorator to throttle the ajax request, the throttle callback function is not bound to the DOM element. The result is that 'this' refers to the window element, in the context of the throttle callback. The precondition function gets bind(this) called on it, but it's the wrong 'this'. I think that the throttle callback should be bound to 'this' at the time the callback is defined.
> AbstractDefaultAjaxBehavior#throttleScript(...) should be changed from:
> return new AppendingStringBuffer("wicketThrottler.throttle( '").append(throttleId)
> 			.append("', ")
> 			.append(throttleDelay.getMilliseconds())
> 			.append(", function() { ")
> 			.append(script)
> 			.append("});");
> to:
> return new AppendingStringBuffer("wicketThrottler.throttle( '").append(throttleId)
> 			.append("', ")
> 			.append(throttleDelay.getMilliseconds())
> 			.append(", function() { ")
> 			.append(script)
> 			.append("}.bind(this));");

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