[webkit-dev] Limiting slow unload handlers (Re: Back/forward cache for pages with unload handlers)

[Maciej Stachowiak]

On Oct 14, 2009, at 6:43 PM, John Abd-El-Malek wrote:

> To resurrect this thread.  I'm looking in implementing some of the  
> methods that we discussed so that web developers have no excuse in  
> simulating sleeps in unload handlers.

...

> -Image trick (image loads started from unload handlers outlive the  
> page): simple, maintains comparability with IE and existing sites.   
> however a little inelegant and requires JavaScript.

...

> Do we have agreement on proceeding with implementing the Image based  
> approach?

Yes, I think we should let image loads from unload handlers run to  
completion. I don't see much downside, and the compatibility with IE  
behavior is pretty compelling.

The other ideas you mentioned don't seem as good. Making a new API or  
a new XHR flag would be WebKit-specific and thus inferior to the Image  
thing. And I think <a ping>, though it may have its uses, does not  
apply to this use case. Dynamically creating an <a> element and  
sending it a fake click event is rather awkward. And navigations  
initiated from the unload handler do not actually happen. It would be  
weird to special-case things so that the ping is sent anyway, even  
though the navigation does not go through. Let's reserve <a ping> for  
hyperlink auditing and not bend it to the purpose of page close  
auditing.

Regards,
Maciej