[webkit-dev] GlobalScript in WebKit

Maciej Stachowiak mjs at apple.com
Mon Nov 30 19:55:53 PST 2009

On Nov 30, 2009, at 6:16 PM, Drew Wilson wrote:

> Following up, I think this highlights the distinct set of use cases  
> that shared workers and shared script address:
> SharedWorkers are a great platform for when you have a single  
> database that is shared across multiple instances of your web app,  
> and you want to coordinate updates to that database. I can imagine  
> sharing a single connection to the server, etc via SharedWorkers.
> SharedScripts are a good platform for when you want to share data/ 
> code (for example, the immense body of Javascript used to implement  
> the Gmail UI) across multiple windows. I can't speak to whether  
> passing a hidden iframe between windows as was suggested in the  
> other thread would address this use case sufficiently.

Would it be fair to say the goal for SharedScript is just to share  
code and data (to reduce memory use of multiple instances of GMail),  
and not network connections, timers, or other APIs based on async  
callbacks (assuming those either remain per-Window or are in the  
SharedWorker)? If so, then it would pretty much completely be handled  
by sharing of some arbitrary JavaScript object, possibly arranged by  

Sharing an out-of-document HTMLIFrameElement would almost even account  
for timers and the like, except that currently in WebKit a frame's  
Window does not exist and its contents are not loaded if the frame is  
not rendered.

  - Maciej

> -atw
> On Mon, Nov 30, 2009 at 6:11 PM, Drew Wilson <atwilson at google.com>  
> wrote:
> I believe that the offline gmail team uses the Gears flavor of  
> shared workers and is planning to migrate to the HTML5 version once  
> DB access is supported from within worker context in shipping  
> browsers.
> So I guess that Gmail would be a candidate app that has asked for  
> both.
> -atw
> On Mon, Nov 30, 2009 at 6:08 PM, Maciej Stachowiak <mjs at apple.com>  
> wrote:
> On Nov 30, 2009, at 3:43 PM, Dmitry Titov wrote:
> I don't think it's correct to say that SharedWorkers are not useful  
> and "we need a SharedScript instead". They are different things and  
> can address different use cases. For example, SharedWorker is great  
> to make sure there is only one 'app instance' running - exactly  
> because it is shared inter-process, it can be used as a "inter- 
> process synchronization primitive" to control how many app instances  
> are opened. SharedScript is a container for data and code shared  
> between pages that comprise a "web application" and normally run in  
> the same process. As in native apps, whether or not multiple  
> instances of the app can run at the same time depends on the author  
> of the app, and can be done either way.
> Are there any Web apps at Google or elsewhere currently using  
> SharedWorker? Would any of them still use it if they could switch to  
> SharedScript? Has any app team specifically requested support for  
> *both* SharedWorker *and* SharedScript? (Serious questions, since  
> the justification for SharedScript is largely based on Web developer  
> feedback.)
> Note: if SharedScript was really globally shared it could be used to  
> implement shared workers - simply have the SharedScript manage the  
> per-app Workers.
> Regards,
> Maciej
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> webkit-dev at lists.webkit.org
> http://lists.webkit.org/mailman/listinfo.cgi/webkit-dev

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