[whatwg] style sheet blocking scripts

[James Robinson]

On Wed, Dec 9, 2009 at 3:19 PM, Jonas Sicking <jonas at sicking.cc> wrote:

> On Wed, Dec 9, 2009 at 3:18 PM, Jonas Sicking <jonas at sicking.cc> wrote:
> > On Wed, Dec 9, 2009 at 3:06 PM, James Robinson <jamesr at google.com>
> wrote:
> >> On Wed, Dec 9, 2009 at 2:57 PM, Jonas Sicking <jonas at sicking.cc> wrote:
> >>>
> >>> On Wed, Dec 9, 2009 at 2:10 PM, James Robinson <jamesr at google.com>
> wrote:
> >>> > 2009/12/9 tali garsiel <t_garsiel at hotmail.com>
> >>> >>
> >>> >> Well, not completely.
> >>> >> Regarding the first question- Webkit guys told me (on their IRC
> >>> >> channel)
> >>> >> that the don't block the parser and only block scripts that request
> >>> >> visual
> >>> >> information, so I'm still  confused.
> >>> >
> >>> > Here's my understanding of the implementation inside WebKit
> currently:
> >>> > During parsing, WebKit does not block the parser on stylesheet loads,
> >>> > but
> >>> > does block external scripts from running until previously-encountered
> >>> > stylesheets have loaded.  WebKit does not suspend script execution on
> >>> > requests for visual information if stylesheets have not loaded (for
> >>> > example
> >>> > for inline scripts or in the case of stylesheets added dynamically
> after
> >>> > parsing has completed).  WebKit does suspend parsing of the document
> on
> >>> > script loads, but has a speculative preloader to attempt to start
> >>> > fetches
> >>> > for resources past the <script> tag.
> >>>
> >>> Why does webkit treat external scripts different from inline scripts
> >>> here? I.e. why is an inline script allowed to run even if there are
> >>> pending stylesheet loads, but external scripts not? That seems
> >>> inconsistent and confusing.
> >>>
> >>> Is this considered a bug or desired behavior?
> >>
> >> The
> >> former:
> http://trac.webkit.org/browser/trunk/WebCore/html/HTMLTokenizer.cpp#L2017
> >> I'm not sure how much this matters in practice.  In theory, this is
> >> unobservable to the page unless it queries the loaded stylesheets
> directly
> >> or a property derived from layout both of which should suspend script
> >> execution.
> >
> > Why is this more "in theory" for inline scripts than for external
> scripts?
>
> Or rather, why is this more unobservable for inline scripts than for
> external scripts?
>

You're right, there's no real difference in the observability of this
behavior for inline vs external scripts.

- James


>
> / Jonas
>
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