[webkit-qt] webkit2, v8, diplomacy

Coda Highland chighland at gmail.com
Tue Jun 5 06:12:01 PDT 2012

On Tue, Jun 5, 2012 at 7:53 AM, Balazs Kelemen <kbalazs at webkit.org> wrote:
>     Hi all!
> I think it's time to decide how important is the v8 integration for us. I'm
> not saying it's hyper-super important, I'm just curious about your opinion.
> In fact we have a qt5 release blocker bug for that:
> https://bugs.webkit.org/show_bug.cgi?id=76778 (although at the time when it
> has been filed we did not expect that much community resistance) and it's
> also quite clear that this could save a lot of memory (1 js engine instead
> of 2). It's evident that we don't want to go against the community, but
> still I think they should be more open to this. It's really just some lines
> of boilerplate glue code to webkit2, and we choose a solution that provides
> source compatibility with WebKitTestRunner. Btw, there are the bugs:
>     - https://bugs.webkit.org/show_bug.cgi?id=76778 (meta)
>     - https://bugs.webkit.org/show_bug.cgi?id=87872 shim for wtr
>     - https://bugs.webkit.org/show_bug.cgi?id=84457 wk2+v8
> If the case is that we want to go for this, I would definitely need your
> help to get community acceptance since I'm not a reviewer and honestly I am
> not very good in diplomacy :)
> Anyway, I would not like to make the false illusion that pushing these
> patches will solve every problem and just save memory. In fact, in order to
> get the desired benefit we have to solve other issues:
>     - using the same copy of v8 (fork) in declarative and webkit. this is
> tricky because webkit needs the most up-to-date v8 version
>     - using v8 in qtscript, or detaching qtscrpit from qtdeclarative (I
> heard qtscript is a dependency)
> Cheers,
> -kbalazs

I don't understand why the push for V8 in the first place. JSC and V8
are in an arms race for performance, so you can't categorically say V8
is faster because that's not always true. JSC also has broader support
(see Konstantin's post). Furthermore, my understanding is that V8
doesn't expose the necessary APIs to be able to provide the full scope
of the QtScript API. (Has this changed since the original plans to
move to V8 were announced?)

Is there some specific feature that makes V8 qualitatively superior to
JSC for Qt's use cases? So far I've not seen anything that really
sells me on the idea.

/s/ Adam

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