[webkit-dev] GlobalScript API.

Maciej Stachowiak mjs at apple.com
Mon Aug 31 19:18:18 PDT 2009

On Aug 31, 2009, at 6:09 PM, Dmitry Titov wrote:

> Hi WebKit-dev,
> I'm hoping to get your advice on Global Script proposal and how to  
> start implementing it as an 'experimental API' since it's not  
> standardized yet.
> As part of work on Workers in WebKit and Chromium, we discussed them  
> with our web application folks (mostly gmail). We came to the idea  
> that in addition to workers, they need a shared script context which  
> runs on the same UI thread and directly scriptable.
> Our previous take (with an invisible window running all the time in  
> the background) was not that fruitful but it indicated the way to  
> go. We are thankful to the members of the whatwg community for the  
> detailed threat analysis of 'permanently running invisible pages',  
> it helped very much. Not right away but it was absorbed :-) Current  
> proposal reflects realization that there is a less-powerful way to  
> achieve the same benefits.
> I'm looking for a way to implement it as an experimental API in  
> WebKit and Chromium. I'm thinking it can go the similar way as  
> webkitNotifications - surrounded by ENABLE(GLOBAL_SCRIPT) and  
> prefixed with 'webkit' to keep the difference.

Here's what I think we should take a look at:

1) Does this proposal have a potential standards-track future?  
Relevant specific issues would be interest from other browser vendors  
and standards folks, interest from content producers, and our own  
degree of confidence that this is the right approach. Note: in some  
cases a prototype can be the best way to address concerns, however. In  
some cases we're willing to add proprietary extensions that have  
little hope of ever becoming a standard, but almost always we do this  
for the sake of non-browser use.

2) Do we have some agreement in the WebKit community that this is a  
good approach? It would be good for us to do some of our own design  
review, if this isn't going to be a standard in the foreseeable future.

If we are optimistic about the future, then an ENABLE macro and a  
WebKit prefix would be a good way to handle things.

I will do some detailed design review soon.


> I'd appreciate much your advice on the whole API and on the way to  
> bring it into WebKit.
> Here is a link to the whatwg thread, with the proposal and use  
> cases: http://lists.whatwg.org/htdig.cgi/whatwg-whatwg.org/2009-August/022113.html
> Here is an actual API:
> ---------------------------
> Page-level API
> var globalScript = new webkitGlobalScript(name, url, loadHandler,  
> errorHandler);
> This returns a global scope object for the named Global Script.
> If one does not exist yet, creates a new one. The globalScript is
> sharing same process and same thread as the page running the  
> constructor
> and is operational right away. No synchronization is necessary.
> Parameters:
> name - string identifying the global script. Scoped to the orogin.
> url  - the JS resource to load, if it was not yet loaded. If the  
> Global Script is already loaded but from a different url - the error  
> is raised.
> laodHandler - a function called asynchronously when the script is  
> loaded (or if it was already loaded by another page)
> errorHandler - handler for loading errors, like violation of same- 
> origin policy or network error
> The GlobalScript would create its own ScriptExecutionContext-derived  
> context if it was not yet created, and start to load the script into  
> it. Once the script is loaded, it is evaluated in the global scope  
> of the Global Script and loadHandlers are executed. Other pages that  
> create a Global Script with the same name in the same origin would  
> get the same object back.
> The globalScript object returned from the constructor can be  
> immediately used to set/retrieve properties and event handlers on it.
> API exposed to Global Script (on its global scope object)
> - Timers
> - XHR
> - Navigator
> - localStorage
> - Database
> - Workers
> -----------------------------
> Thanks,
> Dmitry
> _______________________________________________
> webkit-dev mailing list
> webkit-dev at lists.webkit.org
> http://lists.webkit.org/mailman/listinfo.cgi/webkit-dev

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